VARIABLE RATE NITROGEN AND SEEDING TO IMPROVE NITROGEN USE EFFICIENCY TABITHA THERISA BROWN

Transcription

1 VARIABLE RATE NITROGEN AND SEEDING TO IMPROVE NITROGEN USE EFFICIENCY By TABITHA THERISA BROWN A disserttion submitted in prtil fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY WASHINGTON STATE UNIVERSITY Deprtment of Crop nd Soil Sciences DECEMBER 2015 Copyright by TABITHA THERISA BROWN, 2015 All Rights Reserved

2 Copyright by TABITHA THERISA BROWN, 2015 All Rights Reserved

3 To the Fculty of Wshington Stte University: The members of the Committee ppointed to exmine the disserttion of TABITHA THERISA BROWN find it stisfctory nd recommend tht it be ccepted. Dvid R. Huggins, Ph.D., Chir John Regnold, Ph.D. C. Kent Keller, Ph.D. Chd E. Kruger, M.S. Jeffery L. Smith, Ph.D., Honorry ii

4 ACKNOWLEDGEMENTS I owe tremendous mount of thnks to my committee for their time, support nd encourgement during our reserch dventures tht shped this disserttion. The crew in the Huggins lb performed much of the work in this disserttion nd through lughter the tedious work wsn t so bd. Fmily nd friends suffered from occsionl grumpiness nd feisty outbursts during the entire PhD process nd I wish to pologize for tht. And express my grtitude for their love nd support. The ptience nd fortitude of Clyde improved my mentl stte, sort of, nd I feel blessed for ll the things lerned long the wy. I would like to cknowledge the following sources of finding: Nitrogen Science Policy-oriented Integrted Reserch nd Eduction-IGERT (NSPIRE-IGERT); USDA-NIFA Site-Specific Climte Friendly Frming Project (SCF); nd USDA-NIFA Regionl Approches to Climte Chnge (REACCH). iii

5 VARIABLE RATE NITROGEN AND SEEDING TO IMPROVE NITROGEN USE EFFICIENCY Abstrct by Tbith Theris Brown, Ph.D. Wshington Stte University December 2015 Chir: Dvid R. Huggins Incresed nitrogen (N) fertilizer dditions to modern griculturl cropping systems will be necessry to feed growing world popultion. However, greter nitrogen use efficiency (NUE) is required if groecosystems re to continue to provide certin ecosystem services (e.g., greenhouse gs emission reductions nd wter qulity gols). The im of this reserch ws to investigte the role of vrible rte N nd seeding of winter whet (Triticum estivum) for optimizing yield-wter-nue reltionships cross heterogeneous lndscpes. Field plot studies were conducted t the Cook Agronomy Frm (CAF) ner Pullmn, WA during the 2010, 2011 nd 2012 winter whet hrvest yers. A rndomized complete block split plot N rte x seeding rte experiment with N fertilizer rte s min plot nd seeding rte s subplot ws employed cross three lndscpe positions. Assessed were evidence of hying-off, depletion of vilble wter resources, nd the link between yield, protein, nd NUE response to lndscpe by N fertiliztion rte by seeding rte tretment combintions. A performnce clssifiction ws developed to evlute whet performnce with regrd to N utiliztion efficiency (Gw/Nt) nd N uptke efficiency (Nt/Ns) components of the NUE. iv

6 Evidence of hying-off in winter whet ws medium to high for drier lndscpe positions, prticulrly during low precipittion yers nd likely occurs in these lndscpes most yers. Tretment impcts on NUE vried by yer nd lndscpe but overll NUE decresed by 14 to 22 kg grin yield per kg N supply s N rte incresed from 0 to 160 kg N h -1 cross three lndscpe positions nd two site yers (2011 nd 2012). Trget NUE nd mximum nthesis biomss could be chieved with 34 to 68% reduction in typicl seeding rtes. The NUE-bsed performnce clssifiction ws helpful in identifying environmentl or mngement conditions contributing to low or high NUE indicting potentil to be used s n evlution tool. This reserch lso included policy fellowship focused on N2O emission reductions nd greenhouse gs offset credits tht could be generted from doption of vrible rte N for whet nd concluded tht offset credits lone would not provide enough incentive for doption of vrible rte N. v

7 TABLE OF CONTENTS Pge ACKNOWLEDGEMENTS... iii ABSTRACT... iv LIST OF TABLES... xii LIST OF FIGURES... xvi DEDICATION... xviii CHAPTER 1. Introduction... 1 CHAPTER 2. Evidence of winter whet hying-off in Plouse lndscpes... 7 Introduction... 8 Methods Study: Common methodology Study 1: Plnt Density Experiment with Uniform N Study 2: Nitrogen Rte X Plnt Density Experiment Study 3: Nitrogen Rte Experiment with Uniform Plnt Density nd 2012 N Rte x Seed Rte Studies Sttistics Results Wether Pre-plnt Nitrogen nd Avilble Soil Wter in Spring Evidence of Hying-Off Symptoms vi

8 Evidence Rting for Assessing the Occurrence of Hying-off Reltionship of Kernel Mss to Test Weight Discussion Does Incresing NR nd SPM Led to Hying-off in Dry versus Wet Conditions? Hying-off in Response to NR nd SPM is not Observed in Wet Conditions due to Greter Avilble Wter Identifying Symptoms to Provide Evidence of Hying-off Conclusions References CHAPTER 3. Improving nitrogen use efficiency of winter whet: the role of lndscpe, nitrogen, nd seeding rte Introduction Methods Nitrogen Rte Experiment with Uniform Plnt Density nd 2012 N Rte x Seed Rte Studies Components of N Use Efficiency Aboveground Biomss nd Avilble Soil Wter t Anthesis Sttistics Results Wether Anthesis Biomss nd Remining Avilble Soil Wter Content Nitrogen nd Seeding Rte Effects on NUE vii

9 2010 Hrvest Yer Hrvest Yer Hrvest Yer Person Correltion for Surfce Avilble Soil Wter Content nd Select Vribles Discussion Improving NUE: The Role of N Rte North Bckslopes South Bckslopes Footslopes Summit Improving NUE: The Role of Seed Rte North Bckslope South Bckslope Footslope Implictions Summry nd Conclusions References CHAPTER 4. Developing nitrogen use efficiency performnce criteri to evlute site-specific mngement of whet Introduction Methods viii

10 2010 Nitrogen Rte Experiment with Uniform Plnt Density nd 2012 N Rte x Seed Rte Studies Components of N Use Efficiency Performnce Clssifiction Sttistics Results nd Discussion Grin Yield, Protein, nd NUE Nitrogen Utiliztion Efficiency Nitrogen Uptke Efficiency (Nt/Ns) nd Relted Components Avilble Nitrogen Uptke Efficiency (Nt/Nv) nd Nitrogen Retention Efficiency (Nv/Ns) Performnce Clssifiction: Evlution Tools for Assessing Ecophysiologicl Controls on NUE Performnce Clss Performnce Clss Performnce Clss Performnce Clss Performnce Clss Assessing the Performnce Clssifiction s Post-Hrvest Evlution Tool Prediction of Performnce Clsses Future Reserch Conclusions ix

11 References CHAPTER 5. Comprison of quntifiction pproches in offset protocols for griculturl nitrogen mngement: relevnce to Pcific Northwest drylnd griculture Executive Summry Introduction Greenhouse Gs Emissions nd Offsets Generl Description of Pcific Northwest Drylnd Agriculture Offset Credits from Agriculturl Nitrogen Mngement Agriculturl N mngement to reduce N2O emissions Eligibility Requirements Eligible N Sources Approved N Mngement Activities Mngement Options to Reduce N Fertilizer Rtes for PNW Whet Description of Smple Projects Smple Projects 1 nd 2: Switch from Hrd Red to Soft White Whet Clss Smple Project 3: Switch from Uniform to Vrible N Rte Appliction Impct of Emission Fctor for Direct N2O Emissions Quntifying emission reductions Sources nd Sinks Included in Emission Quntifiction Additionl to Business s Usul Lekge Defult Vlues for Clculting Direct nd Indirect N2O Emissions x

12 N2O emissions for smple projects using pplicble protocols Emissions for Smple Projects 1 nd 2 by Protocol nd Bseline Approch Offsets Generted for Smple Projects 1, 2 nd Smple Project 4: Influence of Regionl Emission Fctors Is this Enough to Impct Mngement Decisions? Conclusions nd Implictions Future Considertions References CHAPTER 6. Conclusions APPENDIX xi

13 LIST OF TABLES Tble Pge 2.1 Lndscpe position chrcteristics for N fertiliztion rte by winter whet seeding rte experiments conducted t the Cook Agronomy Frm during , nd crop yers Mens nd rnges for vrible relted to hying off nd crop growth for the three studies of the 2010 site yer Mens nd rnges for vrible relted to hying off nd crop growth for the 2011 nd 2012 site yers Criteri for evluting the evidence of hying-off using yield, test weight, hrvest index, nd grin protein concentrtion response to incresing N rte or SPM from regression nlysis Hying off symptomology nd evidence rting for the 2010 site yer Hying off symptomology nd evidence rting for 2011 nd 2012 site Yers Probbilities (Pf>F) for winter whet biomss, surfce vilble wter nd subsurfce vilble wter t nthesis by lndscpe, N ppliction rte nd seeding rte by site yer t the Cook Agronomy Frm ner Pullmn, WA Probbilities (Pf>F) for winter whet grin yield nd yield components s ffected by lndscpe, N ppliction rte nd seeding rte by site yer t the Cook Agronomy Frm, ner Pullmn, WA Nitrogen rte effect on nitrogen use efficiency nd components for soft white winter whet by lndscpe for Nitrogen nd seeding rte effect on nitrogen use efficiency nd Components for soft white winter whet by lndscpe for Nitrogen nd seeding rte effect on nitrogen use efficiency nd Components for soft white winter whet by lndscpe for Person correltion coefficients between surfce soil vilble wter (0-90-cm) t nthesis nd select vribles for the 2011 nd 2012 winter whet hrvest yers Averge grin yield, protein, nd N use efficiency components by performnce clss cross ll dt points xii

14 4.2 Additionl N use efficiency components verged by performnce clss cross ll dt points Averge grin yield components nd wter dt by performnce clss cross ll dt points Cross Vlidtion Results for Discriminnt Anlysis using Tretments (Lndscpe, N Rte, nd Seeding Rte), Grin Yield, Grin Protein Concentrtion, Ng/Nt nd Ng/Nf s best predictors Greenhouse gs offset progrms with griculturl nitrogen mngement protocols in North Americ Reviewed quntifiction protocols for griculturl nitrous oxide emissions methodology Eligible Conditions nd Prctices for Agriculturl Nitrogen Mngement Offset Protocols Emission Sources nd Sinks Included in Clcultion of Bseline nd Project N2O Emissions by Protocol Quntifiction Approches for Bseline nd Project Emissions Comprison of Approches for Clculting Direct nd Indirect N2O Emissions Direct nd Indirect Emissions for Bseline nd Project Conditions under Tier I nd Tier II Approches for Quntifying Direct N2O Emissions Nitrous Oxide Emission Reduction Potentil nd Offset Credit Incentive for the Agriculturl N Mngement Smple Projects Including the Fertilizer Cost Svings for Clculting the Offset Credit Incentive for the Agriculturl N Mngement Smple Projects tht Reduce N2O Emissions Pyment Incentive of Smple Project Activities Reltive to Returns over Whet Production Costs A-3 Cumultive monthly precipittion () nd growing degree dys using 0 C bse (b) for ech site yer s compred to norml xiii

15 A : regression equtions, djusted r 2 nd probbilities. Only liner or qudrtic trends were tested for significnce t the 10% level A : regression equtions, djusted r 2 nd probbilities. Only liner or qudrtic trends were tested for significnce t the 10% level A : regression equtions, djusted r 2 nd probbilities. Only liner or qudrtic trends were tested for significnce t the 10% level A-7 Nitrogen use efficiency nd components terminology A-8 A-9 Nitrogen nd seeding rte effect on winter whet biomss, surfce vilble wter nd subsurfce vilble wter t nthesis by lndscpe for Nitrogen nd seeding rte effect on winter whet biomss, surfce vilble wter nd subsurfce vilble wter t nthesis by lndscpe for A-10 Additionl Informtion on N2O Emission Protocol Fetures Reltive Mrket Shre of Offset Credits by GHG Offset Progrm All Reported Defult Fctors for Quntifying N2O Emissions by Protocol A-11 N Fertilizer Dt Needed for Clcultion of N2O Emissions Dt Sources nd Assumptions for Bseline N2O Emissions Quntifiction Field Specific N Fertiliztion Rte nd Yield Dt from the Cook Agronomy Frm Dtbse Yield Gol Bsed N Rte Clcultion for County Level Dt Approch County level yield dt for Whitmn County, WA from United Sttes Deprtment of Agriculture Ntionl Agriculture Sttistics A-12 Exmple Clcultion of Bseline nd Project N2O Emissions Exmple Clcultion of N2O Emissions for Bseline nd Project Activities for Smple Project xiv

16 A-13 Wshington Whet Sttistics for The Totl Are under Whet Production by Clss for Wshington Stte in A-14 Quntifying the Finncil Incentive of Offset Mrkets Totl N2O Offset Credit Incentive for Project Scenrios t the Field Level Cost Svings from Reducing N Fertilizer Rte for Smple Projects 1, 2, nd Whet Prices from Port of Portlnd for 2008 to 2013 t the Port of Portlnd Return over Vrible Costs of Growing Hrd Red Whet compred to Soft White Whet Clsses xv

17 Figure LIST OF FIGURES Pge 2.1 Cumultive precipittion () nd growing degree dys (b) Avilble wter in the 150-cm soil profile during the winter whet growing seson for 2010 (), 2011 (b) nd 2012 (c) winter whet hrvest yers Regression trends in grin yield (), grin protein concentrtion (b), Hrvest index (c) nd test weight (d) in response to incresing SPM for the 2010 Plnt Density Experiment with Uniform N Regression trends in grin yield (), grin protein concentrtion (b), hrvest index (c) nd test weight (d) in response to incresing SPM for the 2010 Nitrogen Rte X Plnt Density Experiment Regression trends in grin yield (), grin protein concentrtion (b), hrvest index (c) nd test weight (d) in response to incresing SPM for the 2010 Nitrogen Rte Experiment with Uniform Seeding Rte Regression trends in grin yield ( nd e), grin protein concentrtion (b nd f), hrvest index (c nd g) nd test weight (d nd h) in response to incresing NR nd SPM for Regression trends in grin yield ( nd e), grin protein concentrtion (b nd f), hrvest index (c nd g) nd test weight (d nd h) in response to incresing NR nd SPM for Reltionship between kernel mss nd test weight for 2010 (), 2011 (b), nd 2012 (c) cross ll tretments Interction plots for significnt N rte by seed rte effect on vilble N uptke efficiency (p =0.0187) observed in 2012 winter whet plots t Cook Agronomy Frm, ner Pullmn, WA Nitrogen nd Seed rte effect on winter whet boveground biomss, vilble wter in the surfce 0 to 90-cm, nd vilble wter in the subsurfce 90 to 150-cm t nthesis for north, foot, nd south slope position in Nitrogen nd Seed rte effect on winter whet boveground biomss, vilble wter in the surfce 0 to 90-cm, nd vilble wter in the subsurfce 90 to 150-cm t nthesis for north, foot, nd south slope position in xvi

18 4.1 Dichotomous key to clssifiction of soft white winter whet performnce bsed on N use efficiency criteri of N utiliztion efficiency (Gw/Nt) nd N uptke efficiency (Nt/Ns) Grin yield, grin protein nd N supply reltionships for ll lndscpe by N rte by seed rte plot dt between 2010 nd 2012 by Performnce Clssifiction The reltionship between N use efficiency, N utiliztion efficiency, grin yield, nd grin protein concentrtion by Performnce Clssifiction for ll lndscpe by N rte by seed rte plot dt between 2010 nd The grin yield nd grin protein reltionship to N uptke efficiency for ll lndscpe by N rte by seed rte plot dt from 2010 to 2012 by Performnce Clss Frequency of performnce clsses by site yer (), lndscpe (b), N rte (c) nd seed rte (d) Emission estimtes from EPA Inventory of U.S. Greenhouse Gs Emissions nd Sinks from by ) mjor U.S. economic sector nd b) N2O emission sources (USEPA, 2013) Emissions for Smple Projects 1 nd 2 by Protocol nd Bseline Quntifiction Approch Emissions for Bseline nd Project Activities under ACR2 nd VCS Quntifiction Methodologies Offset Credits for Project Activities under Tier I nd Tier II Direct N 2 O Emission Fctors A-2. Field plot loction t the Cook Agronomy Frm Plot () nd supporting dt for site selection of soil orgnic crbon contents for surfce 30-cm (b) nd reltive yield mps from hrvest yers (c) A-8b. Field plot loction t the Cook Agronomy Frm Plot () nd supporting dt for site selection of soil orgnic crbon contents for surfce 30-cm (b) nd reltive yield mps from hrvest yers (c) A-9b. Field plot loction t the Cook Agronomy Frm Plot () nd supporting dt for site selection of soil orgnic crbon contents for surfce 30-cm (b) nd reltive yield mps from hrvest yers (c) xvii

19 Dediction This disserttion is dedicted to Dr. Jeff L. Smith whose untimely bsence is felt deeply. In the science nd in the lughter. And in the length of this disserttion! xviii

20 CHAPTER ONE INTRODUCTION Incresing the efficiency with which synthetic nitrogen (N) fertilizers re used to produce modern crop yields remins n importnt griculturl gol tht ligns well with chieving environmentl qulity stndrds nd frm economic profitbility (Hrgrove et l., 1988; Huggins nd Pn, 1993). There is continued interest in further improvements to griculturl nitrogen use efficiencies (NUE) in the fce of globl chllenges, such s climte chnge, tht re ssocited with rising levels of Nr entering the environment (Hrgrove et l., 1988; Vitousek et l., 1997; Gllowy et l., 2003; Robertson nd Vitousek, 2009). However, the current humn popultion growth rte will require incresed food production nd subsequently greter mnufcture nd ppliction of N fertilizer to croplnds (Robertson nd Vitousek, 2009). Therefore, continued improvements in the NUE of modern griculturl systems without compromising yield re needed (Fiez et l., 1995; Huggins, 2010; Robertson nd Vitosek, 2009). Site-specific N fertilizer mngement, otherwise known s vrible rte mngement, is considered one of the most prcticl strtegies for improving griculturl NUE nd reducing N loss to unintended portions of the environment (Cssmn et l., 2002; Robertson nd Vitousek, 2009). Site-specific mngement involves vrying the ppliction of n input or mngement in mnner tht ccounts for vribility in soil properties, pest nd disese incidence, nd crop physiologicl sttus (Cssmn, 1999). In principle this involves pplying mngement, such s N fertiliztion, t the right rte, right time, right plce nd using the right source in order to ccount for sptil nd temporl vribility cross given lndscpe. Adoption of vrible rte mngement strtegies in the Plouse region of the Pcific Northwest, USA is desirble due to 1

21 the complex soil fertility nd crop productivity ptterns observed cross frm fields (Mull et l., 1992). The Plouse region, however, continues to be typified by uniform ppliction of N fertilizer inputs (Fiez et l., 1995). Uniform mngement is thought to contribute to inefficient use of N (i.e., fertilizer N, residul, nd minerlized orgnic N) nd other inputs (e.g., seed nd herbicides) while lso incresing the risk for environmentl degrdtion. Lndscpe scle understnding of vrition in soil processes nd gronomic fctors (e.g., yield gol, vrible seeding nd N) importnt for employing greenhouse gs mitigtion strtegies using vrible rte techniques in the Plouse is needed. Lrge rnges in NUE (Gw/Ns) hve been reported with griculturl fields of the Plouse (Sowers et l., 1994; Fiez et l., 1995; Huggins et l., 2010). Sowers et l. (1994) observed NUE to rnge from 18 to 24 kg grin per kg -1 N supply for soft white winter whet cross two field sites nd two crop yers. Fiez et l. (1995) reported NUE to rnge from kg grin per kg -1 N supply for soft white winter whet cross different lndscpe positions within fields during two growing sesons. In 2010, Huggins et l. observed rnge in NUE of 4-34 kg grin per kg -1 N supply for hrd red spring whet cross 37 h field. This rnge in N use efficiencies observed cross lndscpes of the Plouse occurs, in prt, s result of vribility in yield response to uniform N fertilizer pplictions (Huggins nd Pn, 1993). The ptterns in yield response nd extremes in NUE indicte tht uniform ppliction of N fertilizer inputs will not be sufficient to simultneously chieve grin yield, protein, nd NUE gols (Huggins et l., 2010b). The potentil economic dvntge from improvements in NUE continues to stimulte interest in precision frming technologies to pply N fertilizers site specificlly to better mtch 2

22 crop demnd with N supply (Huggins et l., 2010). In the Plouse, the mjor fctors involved in most N mngement decisions, such s potentil yield, N vilbility, N uptke efficiency nd N losses, exhibit both sptil nd temporl vribility (Huggins, 2010). Though comprehensive reviews on NUE exist, ssessment nd decision support relevnt to prcticl field scle N mngement remin insufficient to encourge doption of site-specific mngement (Cssmn et l., 2002; Dobermn, 2007). Tht is, the success of site-specific N mngement will require grower-oriented field-scle decision support tools to evlute if site-specific mngement strtegies llowed them to meet their production nd NUE gols (Cssmn et l., 2002; Huggins et l., 2010). The lrge rnge in reported NUE my be due to the interction of genetics (cittion), vribility in crop rottion or sequence, soil nd residue mngement prctices, vilble wter resources, or N fertilizer mngement (Pierce nd Rice, 1988). There re often lrge differences in soil type, vilble soil wter, soil temperture, nd other environmentl conditions tht impct crop development nd growth cross different lndscpe positions of Plouse hills (Mhler et l., 1979; Cih, 1984; Bssinette, 1995; Fiez et l., 1995). This results in lndscpe fctors cting s importnt environmentl drivers of crop development nd the fte of pplied N. Furthermore, improving crop yield nd NUE under drylnd crop production requires simultneous understnding of soil wter nd N dynmics (Fuentes et l., 2003). In the Plouse region drylnd frming relies hevily on stored soil moisture. Wter redistribution mong lndscpe positions s well s the timing nd mount of spring precipittion re lso importnt in determining grin yield (Pn et l., 2007). Wter re- 3

23 distribution in the complex topogrphy of the Plouse my result in some loctions within field experiencing extreme wter stress while others my provide dequte plnt vilble moisture in ny given yer. Given this, the following question ws posed: Should vrible rte seeding be considered in conjunction with vrible rte N in order to chieve greter NUE improvements? This reserch ws therefore imed t exmining winter whet crop response to vrible rte N nd seeding cross different lndscpe positions. The overrching gol ws to gin n understnding if tiloring winter whet seeding rtes to site-specific environments cn id in chieving the optimum plnt popultion to efficiently utilize the N supply nd vilble wter resources while lso optimizing crop yield nd yield qulity. This reserch is therefore divided into four min chpters tht follow. Chpter two investigted the occurrence of hying-off by simultneously exmining grin yield, grin protein concentrtion, hrvest index, nd test weight response to incresing N fertiliztion nd seeding rte cross yers nd lndscpe positions. Chpter three included n evlution of N fertilizer nd seeding rte tretments on NUE nd vilble soil wter depletion mong wet versus dry conditions. Chpter four involved the development of NUE performnce clssifiction for whet bsed on NUE criteri from regionl fertilizer guides nd ssessment of the clssifiction s post-hrvest evlution tool for site-specific N or seed rte mngement. A rod test of griculturl N mngement protocols for ddressing the role of N bsed GHG offset progrms in the drylnd Pcific Northwest (PNW) whet-bsed cropping systems is ddressed in Chpter five. Finlly, Chpter Six, Conclusions, provides summry nd ties together the previous four chpters, including some finl closing comments. 4

24 REFERENCES CITED Bssinette, J.P Plnting dte, cultivr nd seeding rte effects on winter whet, spring whet nd spring brley gronomic performnce nd decision to replnt. University of Idho Msters Thesis. Cssmn, K.G Ecologicl intensifiction of cerel production systems: yield potentil, soil qulity, nd precision griculture. Proc. Ntl. Acd. Sci. 96: Cssmn, K.G., A. Dobermnn, nd D. T. Wlters Agroecosystems, nitrogen-use efficiency, nd nitrogen mngement. Ambio. 31(2): Cih, A.J Slope position nd grin yield of soft white winter whet. Agron. J. 76: Dobermn, Nutrient use efficiency mesurement nd mngement. In Fertilizer Best Mngement Prctices First Edition. Interntionl Fertilizer Industry Assocition, Pris, Frnce. pgs Fiez et l., Nitrogen use efficiency of winter whet mong lndscpe positions. Soil Sci Soc. Am. J. 59: Fuentes, J.P Influence of tillge on soil properties under griculturl nd nturl pririe systems. Gllowy, J.N., J. D. Aber, J.W. Erismn, S.P. Seitzinger, R.W. Howrth, E. B. Cowling, nd B.J. Cosby The nitrogen cscde Bioscience. 53(4): Hrgrove, W.L., A.L. Blck, nd J.V. Mnnering Cropping strtegies for efficient use of wter nd nitrogen: Introduction. In Cropping strtegies for efficient use of wter nd nitrogen. Eds. Hrgrove et l. ASA Specil publiction number 51. p 1-5. Huggins, D.R. nd W.L. Pn Nitrogen Efficiency Component Anlysis: An evlution of cropping system differences in productivity. Agron. J. 85: Huggins, D Site-specific N mngement for direct-seed cropping systems. Chpter 16 in Kruger, C., G. Yorgey, S. Chen, H. Collins, C. Feise, C. Frer, D. Grntstein, S. Higgins, D. Huggins, C. McConnell, K. Pinter, C. Stöckle Climte Friendly Frming: Improving the Crbon Footprint of Agriculture in the Pcific Northwest. CSANR Reserch Report Wshington Stte University: Friendly-Frming-Finl-Report/. 5

25 Huggins, D., W. Pn, nd J. Smith Yield, protein nd nitrogen use efficiency of spring whet: evluting field-scle performnce. Chpter 17 in Kruger, C., G. Yorgey, S. Chen, H. Collins, C. Feise, C. Frer, D. Grntstein, S. Higgins, D. Huggins, C. McConnell, K. Pinter, C. Stöckle Climte Friendly Frming: Improving the Crbon Footprint of Agriculture in the Pcific Northwest. CSANR Reserch Report Wshington Stte University: Mhler, R.L., D.F. Bezdicek, nd R.E. Witters Influence of slope position on nitrogen fixtion nd yield of dry pes. Agron. J. 71: Mull, D.J., A.U. Bhtti, M.W. Hmmond, nd J.A. Benson A comprison of winter whet yield nd qulity under uniform versus sptilly vrible fertilizer mngement. Agric. Ecosys. Environ. 38: Pn, W.L., W. Schillinger, D. Huggins, R. Koenig, nd J. Burns Fifty yers of predicting whet nitrogen requirements in the Pcific Northwest U.S.A. Pierce, F.J. nd C.W. Rice, Impct of crop rottion on wter nd N use. In Cropping strtegies for efficient use of wter nd nitrogen. Eds. Hrgrove et l. ASA Specil publiction number 51. p Robertson, G.P., P.M. Vitousek Nitrogen in griculture: blncing the cost of n essentil resource. Annu. Rev. Environ, Resour. 34: Sowers, K.E., B.C. Miller, nd W.L. Pn Optimizing yield nd grin protein in soft white winter whet with split nitrogen pplictions. Agron. J. 86:

26 CHAPTER TWO EVIDENCE OF WINTER WHEAT HAYING-OFF IN PALOUSE LANDSCAPES ABSTRACT In drylnd, whet-bsed cropping systems where wter limits yield nd the potentil for hying-off exists, understnding the reltionship between mngement, crop growth, nd wter use re criticl. The objectives of this reserch were to: (1) ssess evidence for hying-off of winter whet in response to different N fertiliztion by seeding rte tretment combintions cross different lndscpe positions; nd (2) identify symptoms tht provide cler nd quntittive evidence of hying-off. A rndomized complete block, split-plot design with N fertilizer rte (NR) s the min plot (0 up to 160 kg h -1 ) nd winter whet seeding rte (SR) s the subplot (98 up to 335 seeds m -2 ) ws employed cross different lndscpe positions (north bckslope, footslope, south bckslope, or summit) in 2010, 2011, nd Grin yield, grin protein concentrtion, hrvest index nd test weight were used to identify if hying-off occurred. A low, medium nd high evidence rting for evluting the occurrence of hying-off ws developed to more quntittively ssess the mgnitude of hying-off. There ws medium to high evidence of hying-off for drier lndscpe positions (i.e., south bckslopes nd summit) s NR or spikes m -2 (SPM) incresed nd prticulrly under dry wether conditions (i.e., 2010) indicting tht hying-off likely occurs in most yers. In the south bckslope of 2010, where high evidence of hying-off ws observed, significnt qudrtic grin yield tht declined t higher N rtes, ws ssocited with high grin protein (rnge of 71 to 123 g kg -1 ), low hrvest index (rnge of 0.26 to 0.39), nd low test weight (rnge of 66.2 to 75.0 kg hl -1 ). The south bckslope in 2012 exhibited significnt qudrtic grin yield response to NR tht plteued 7

27 nd liner yield increse with incresing SPM tht ws ssocited with protein concentrtion rnge of 72 to 164 g kg -1, hrvest index 0.28 to 0.48 nd test weight of 72 to 80 kg hl -1. These rnges in response showed tht drier lndscpe positions nd drier yers could be N fertilized nd seeded t lower rtes thn wetter lndscpe positions or wetter yers without compromising yield by voiding mngement induced hying-off. Mnging to llow for compenstion mong yield components without contributing to hying-off should trget optimum combintions of N nd seed rte for the driest lndscpe positions tht lso support economicl yields nd yield qulity. INTRODUCTION Hying-off in cerel crops is described s grin yield reduction resulting from excessive vegettive growth tht excerbtes terminl drought during grin filling (vn Herwrden et l., 1998; Angus nd vn Herwrden, 2001). Hying-off hs been ttributed to soil wter deficit during grin filling when: (i) high levels of vilble soil N stimulte vegettive growth nd high soil wter consumption (vn Herwrden et l., 1998; Angus nd vn Herwrden, 2001); nd/or (ii) high plnt popultions result in greter biomss tht increses competition for vilble wter (Fischer nd Kohn, 1966) nd stored ssimiltes t grin filling (vn Herwrden, 1998b). Hying-off is reported to be most pronounced during conditions of terminl drought (i.e., wter deficit fter heding) resulting in reduced post- nthesis ssimiltion (vn Herwrden et l., 1998). Symptoms of hying-off hve been described s the lck of grin yield response or grin yield decline with incresing N supply ssocited with decrese in hrvest index nd grin test weight, n increse in grin protein concentrtion 8

28 nd low post-nthesis vilble soil wter (vn Herwrden et l., 1998). Evidence for hyingoff using symptomology reported in other regions hs not been evluted for ppropriteness under Plouse drylnd cropping systems. To be useful for growers, symptoms of hying-off must be clerly linked to crop growth nd productivity in order to evlute mngement impcts in the bsence of multiple N nd/or seed rte studies. Grin yield in whet (kg h -1 ) is the product of compenstion mong the following components: plnts per unit re, number of spikes per plnt, kernels spike -1, nd weight kernel -1 (Drwinkle, 1978). Plnts per unit re nd number of spikes per plnt cn be combined to provide the spikes m -2 (SPM). Compenstory effects mong cerel yield components cn be expressed in response to mngement by environment interctions nd to lesser extent genotype by environment interctions (Drwinkle, 1978; Cih, 1983; Klepper et l., 1982; Bulmn nd Hunt, 1988). For exmple, Grci del Morl et l. (2003) reported SPM to be the most importnt component contributing to grin yield during non-drought yers, while kernels spike -1 impcted yield the most during extreme wter stress. Vn Heerwrden et l. (1998) suggest using kernel mss in conditions of post-nthesis wter deficit to provide more cler indiction if hying-off occurred. Crop growth, grin yield nd the occurrence of hying-off re strongly influenced by dequte N supply, seeding rte (Drwinkle, 1978; Joseph et l., 1985; Bulmn nd Hunt, 1988) nd totl vilble wter (Tompkins et l., 1991; Schillinger et l., 2008). Nitrogen fertilizer ppliction influences biomss ccumultion, tiller production, spikes m -2, kernels spike -1 nd kernel mss (vn Herwrden et l., 1998; Ali et l., 2011). vn Herwrden et l. (1998) 9

29 found tht the ppliction of N incresed biomss t nthesis, SPM, kernels spike -1, nd kernel number. They reported kernel weight to decrese in response to N fertilizer ddition nd especilly t sites experiencing hying-off (vn Herwrden et l., 1998). Of the yield components, SPM hs been most strongly ssocited with winter whet grin yield (Fiez et l., 1994b; Bssinette, 1995; Grci del Morl et l., 2003) s spike number is one of the first yield components to be determined during the course of crop development (Bulmn nd Hunt, 1988). Whet grin yield hs been observed to increse linerly s SPM increse (Drwinkle, 1978; Bulmn nd Hunt, 1988) but optimum spike densities to chieve mximum yield cn vry from 400 to over 1,000 SPM (Drwinkle, 1978; Joseph et l., 1985; Bulmn nd Hunt, 1988; Holen et l., 2001). Under terminl drought conditions grin yield reductions due to hying-off hve been reported under higher seeding rtes nd ssocited SPM (Cih, 1983; vn Herwrden et l., 1998). The implictions of this re tht compenstion cn be limited by too few spikes but under drought conditions, high SPM produced by incresing the plnting rte, could result in hying-off. Nitrogen nd seeding rte mngement impcts on crop wter use hve been reported by Pwson et l., 1961, Entz nd Fowler, 1989, nd Vn Herwrden et l., Seeding rte impcts on wter use efficiency were observed by Entz nd Fowler (1989) s well s positive correltion between wter use efficiency nd SPM, kernel weight, nd biomss t nthesis. Thompkins et l. (1991) reported significnt seed rte effect on growing seson wter use. They reported 4% greter wter use under higher seeding rtes nd greter vilble soil wter in the low seed rte tretments t nthesis. The high seeding rte, however; still yielded 10

30 more thn the low seeding rte s result of erly seson biomss production (Thompkins et l., 1991). Brown (1971) observed tht incresing mounts of N fertilizer incresed the depth of wter depletion nd cumultive wter use for winter whet. Adjusting winter whet seeding rtes to better mtch vribility in N supply with plnt vilble wter resources my be importnt for optimizing grin yield nd N inputs by reducing mngement induced hying-off. In drylnd cropping systems where wter is limiting nd the potentil for hying-off exists, understnding of the reltionship between N mngement, crop growth, nd wter use re needed. Fiez et l. (1994b) observed tht ddition of N fertilizer incresed yield by incresing the spike density by 65 to 111 spikes m -2 per 100 kg N per h -1 but the effect ws lndscpe specific indicting tht lndscpe fctors re importnt environmentl drivers. Previous reserch in the Plouse region hs shown tht grin yield is strongly dependent on storge of winter precipittion in the soil profile, vilbility of soil wter during the growing seson nd the mount of spring precipittion (Leggett, 1959; Fuentes et l., 2003; Pn et l., 2007; Schillinger et l., 2008). This occurs, in prt, s greter thn 60% of the verge nnul precipittion occurs from October to Mrch in the estern Wshington portion of the Plouse (Fiez et l., 1995; Schillinger nd Ppendick, 2008). There re often lrge differences in soil type, vilble soil wter, soil temperture, nd other environmentl conditions tht impct crop development nd growth cross different lndscpe positions of Plouse hills (Mhler et l., 1979; Cih, 1984; Bssinette, 1995; Fiez et l., 1995). Tiloring whet seeding rtes to sitespecific environments my id in chieving the SPM required to efficiently utilize N supply, vilble wter resources, nd optimize grin yield while voiding hying-off. 11

31 The objectives of this reserch were to: (i) ssess the evidence for hying-off in response to different N fertiliztion by seeding rte tretment combintions cross different lndscpe positions; nd (ii) identify symptoms tht provide cler nd quntittive evidence of hying-off. The specific hypotheses considered in this reserch were: (i) hying-off occurs in drier lndscpe positions (e.g., south bckslopes, summit) t higher N fertilizer ppliction rtes nd spike popultions s compred to wetter lndscpe positions (e.g., north slopes nd footslope positions) or wetter yers; nd (ii) hying off is not exhibited in colder nd wetter lndscpe positions even with higher N supplies nd plnt popultions due to greter post-nthesis wter vilbility. METHODS Field plot trils from the 2010, 2011 nd 2012 winter whet hrvest yers were used to evlute N fertilizer nd seeding rte effects on soft white winter whet yield, yield qulity, yield components nd symptoms of hying-off (Appendix 1). A rndomized complete block, split-plot design with N fertilizer rte (NR) s the min plot nd seeding rte (SR) s the subplot ws employed cross different lndscpe positions (north bckslope, footslope, south bckslope, or summit) t the Cook Agronomy Frm (CAF), ner Pullmn, WA in ech yer (Appendix 2) Study: Common methodology A field scle N rte experiment ws initited on winter whet ( OR102 ) tht hd been plnted under vrible rte N mngement in October of Plot scle experiments were initited in the spring of 2010 within the lrger field-scle N rte study. Winter whet ws 12

32 plnted in pired rows on 12 inches centers using no-till drill (Horsh-Anderson) equipped with hoe type openers. The previous crop ws hrd red spring whet ( Hnk ). Nitrogen fertilizer rtes of 0, 48, 76, nd 104 kg N h -1 s ure mmonium nitrte solution (32-0-0) were pplied t plnting. Ech tretment or tretment combintion for the 2010 studies were 3 m 2 in size Study 1: Plnt Density Experiment with Uniform N Plnt density plots were estblished on one N fertilizer rte tretment (112 kg N h -1 ) on north nd south slope position tht hd been uniformly seeded (240 seeds m -2 ). In the spring of 2010, winter whet plnts were counted in the 3m 2 plots nd then thinned to chieve three plnt popultion tretments of 98, 164, nd 230 plnts m -2. The plnt density tretments were replicted four times in ech lndscpe position Study 2: Nitrogen Rte X Plnt Density Experiment A nitrogen rte x seeding rte experiment ws initited s rndomized complete block split plot design on south fcing bckslope (four replictions) nd summit (two replictions) lndscpe position. Uniformly seeded (240 seeds m -2 ) N fertilizer rte plots on south nd summit lndscpe position were thinned to chieve plnt popultion tretments of 98, 164, nd 230 plnts m -2 within ech N fertilizer tretment. The highest plnt density tretment (230 plnts m -2 ) ws not chieved due to low plnt popultion under the uniform seeding rte of 240 seeds m -2 (dt not shown) Study 3: Nitrogen Rte Experiment with Uniform Plnt Density A plot scle N Rte with uniform plnt density experiment in the north, summit, nd south slope lndscpe positions ws initited in the spring of There were four replictes 13

33 for north nd south slopes nd two replictes for the summit position. Replictes for the summit position were limited by the smll size of the summit lndscpe position for this prticulr field t CAF nd 2012 N Rte x Seed Rte Studies The plots were seeded nd fertilized on 19 cm (7.5 in) row spcing using Fbro no-till double disk plot drill with totl min plot size of 35 m 2 nd subplot size of 8.75 m 2. Nitrogen fertilizer (dry ure, ) ws estblished s the min plot nd bnd pplied below the seed t plnting t rtes of 0, 40, 80, 120, nd 160 kg N h -1. Plnt popultion nd spike density differences were estblished within ech NR strip by seeding t 80, 165, 250, nd 335 seeds m - 2. Soft white winter club whet ( Chukr ) ws plnted on October 13 in both 2011 nd Seed weight nd kernels per pound were determined ech yer to clculte the mount of seed weight required to chieve the desired seeding rtes. The previous crop ws grbnzo bens (Cicer rietinum, Sierr ). Plnt dt used in this reserch included plnt popultion density, spike density, boveground biomss t mturity, grin yield, grin protein concentrtion, kernels per spike, kernel mss nd test weight (TWT) (Appendix 1). Hrvest index (HI) ws clculted s the grin yield (kg h -1 ) divided by the totl boveground biomss (kg h -1 ). In ddition, soil profile inorgnic N content t pre-plnt ws used to ssess lndscpe differences in residul N contributing to hying-off nd response to tretments (Appendix 1). Soil profile vilble wter t tillering, nthesis, nd mturity (i.e., post-hrvest) were lso used to evlute tretment impcts on vilble wter supplies during the growing seson nd wter use efficiency, 14

34 expressed here s the kg h -1 grin yield divided by consumptive vilble wter use between tillering nd mturity (Appendix 1). Growing degree dys were bsed on bse temperture of 0 C nd clculted s dily mximum temperture plus the dily minimum temperture divided by two minus the bse temperture (Krow et l., 1993). Seeding rte tretments were bsed on the number of seeds per unit re rther thn on seed weight per unit re (i.e., kg seed h -1 ) s seed size nd test weight impct ctul seeds h -1 t given seed weight h -1. The seeding rte tretments were designed to mnipulte the production nd survivl of winter whet tillers nd provide rnge in the number of spikes per unit re mong different lndscpe positions. For this study, symptoms of hying-off were defined s the lck of grin yield response or grin yield decline with incresing N rte or plnt popultion (i.e., spikes m -2 ) tht were ssocited with: (i) decrese in HI; (ii) decrese in TWT; nd (iii) increse in grin protein concentrtion. Hrvest index is used to ssess the prtitioning of boveground biomss into vegettive tissue (e.g., leves, stems, chff) nd grin yield. Hrvest index is determined by dividing the grin yield (kg h -1 ) by the totl boveground biomss (kg h -1 ) (Hy, 1995; vn Herwrden et l., 1998). Test weight is volume-weight mesurement tht is used s n indictor for low kernel mss (Morris, 2004) nd provided quntittive rnges to ssess evidence for hying-off in ech lndscpe nd yer of the study. Sttistics The seeding rte tretments resulted in different ctul plnt densities within given tretment nd cross tretments. Therefore, regression nlyses were used to nlyze 15

35 tretment responses with the PROC REG procedure of SAS (SAS 9.4, SAS Inst., 2012). The effect of N rte nd spikes m -2 on grin yield, grin protein concentrtion, HI, TWT, yield components, vilble wter nd wter use ws performed by field (i.e., site yer) nd lndscpe. Where nlysis of vrince ws pproprite, it ws conducted using the PROC MIXED procedure of SAS (SAS 9.4, SAS Inst., 2012) where tretment mens were considered significntly different t p<0.10 nd Tukey s method ws used to control the experiment wise error rte for multiple men comprisons. RESULTS Wether The 30-yer norml nnul precipittion for the re is 53 cm ( , Pullmn 2NW Wether Sttion, Plouse Conservtion Field Sttion). Cumultive nnul precipittion (Oct 1 to Sept. 30) during the study period ws 47-, 61-, nd 58-cm for 2010, 2011, nd 2012, respectively (Figure 2.2). For ll three site yers, the growing seson precipittion (April through August) ws bove the 30 yer norml growing seson precipittion of 16.4 cm (Appendix 3). The growing seson precipittion ws 19.5 cm for 2010, 18.1 cm for 2011, nd 17.5 cm for Even though spring precipittion ws bove norml in 2010, over winter precipittion ws 11% below norml for 2010 leding to reltively droughty conditions overll for the 2010 crop yer (Fig. 2.2). There ws slightly higher thn norml precipittion during both the winter nd spring of Fll nd winter precipittion ws generlly lower thn norml for the 2012 crop yer. 16

36 Colder fll nd slightly wrmer winter nd erly spring conditions were observed in 2010 (Fig. 2.2b). October, November, nd December were 28, 17, nd 20% colder thn norml while Mrch nd April were 11 nd 10% wrmer thn norml (Tble 2.2). In 2011, slightly wrmer conditions were observed from October through April nd slightly colder conditions from My to hrvest compred to norml (i.e., lower GDD thn norml). The 2012 winter whet crop yer hd slightly less growing degree dys (3 to 7% less) during November to Mrch nd slightly more during April to August compred to norml (Fig 2.2). The timing nd mount of precipittion s well s wrmer winter nd spring tempertures ppered to hve fvored higher yields overll in the 2011 crop yer compred to the 2010 nd 2012 crop yers (Fig. 2.3). Pre-plnt Nitrogen nd Avilble Soil Wter in Spring Soil profile (0 to 1.5 m) vilble N in the spring following plnting (fll 2009) rnged from 111 to 184 kg N h -1 in control plots indicting high soil residul N levels for the winter whet crop (Tble 2.1). This ws result of unused N fertilizer remining in the soil profile following low-yielding hrd red spring whet crop. In 2011, there ws greter residul N in footslope (80 kg N h -1 ) compred to the north nd south bckslope positions which hd similr residul N, 59 nd 56 kg pre-plnt N h -1, respectively in control plots (0 pplied N) prior to fll seeding (Tble 2.1). In contrst, there ws significntly greter residul N in the south bckslope (90 kg N h -1 ) compred to north bckslope (66 kg h -1 ) nd footslope (59 kg N h -1 ) positions in 2012 (Tble 2.1). Estimted plnt vilble wter in the surfce 150-cm of the soil profile, over ll tretments, in the spring rnged from 16- to 19-cm, 39- to 44-cm, nd 29- to 44-cm in 2010, 17

37 2011, nd 2012, respectively (Tble 2.1). Avilble wter in the spring ws lowest in the summit in 2010 nd in the south bckslope in both 2011 nd 2012 (Fig. 2.2). Avilble soil profile wter in spring ws gretest in the north bckslope in 2010 nd gretest in the footlslope positions in 2011 nd In 2011, the footslope position ppered to receive wter from uplnd field loctions s vilble soil wter showed little decrese between nthesis nd mturity (Fig. 2.2b). In 2011, the south slope hd slightly (but significntly) lower vilble wter t nthesis thn the north bckslope position but differences were negligible by mturity (Fig 2.2b). In 2012, the footslope hd higher vilble wter t tillering nd nthesis but the north bckslope hd higher vilble wter t mturity (Fig 2.2c). The south bckslope hd the lowest vilble wter throughout the 2012 growing seson (Fig 2.2c). Evidence of Hying-Off Symptoms In 2010, there ws lck of or declining grin yield response to incresing NR nd SPM for the three studies (Appendix 4). In the first study, there ws no yield response in the north bckslope nd significnt liner yield decrese in the south bckslope s SPM incresed (Fig. 2.3, Appendix 4). Over ll plnt density tretments, grin yield rnged from 3010 to 5910 kg h -1 nd from 3530 to 5410 kg h -1 in the north nd south bckslopes, respectively (Tble 2.2). The grin yield decrese in response to greter SPM in the south bckslope ws ssocited with significnt liner increse in grin protein concentrtion, nd liner decreses in HI nd TWT (Fig. 2.3b, 2.3c, nd 2.3d). In the south bckslope, grin protein concentrtion rnged from 95 to 139 g kg -1, HI from 0.28 to 0.35, nd TWT from 66.7 to 74.8 kg hl -1 (Tble 2.2). A significnt 18

38 qudrtic reltionship between SPM nd TWT ws observed in the north bcklope where TWT declined t higher SPM (Fig. 2.3d). In the second study of 2010, there ws no significnt liner or qudrtic grin yield response to NR or SPM in the south or summit lndscpe positions (Fig. 2.4, Appendix 4). Significnt increses in grin protein concentrtions nd significnt declines in HI t higher N rtes nd spike densities indicte moisture-stress in the south bckslope lndscpe position (Fig. 2.4b nd 2.4c). In the south bckslope grin protein concentrtion rnged from 71 to 113 g kg -1 nd HI from 0.31 to 0.43 (Tble 2.2). A decline in HI t greter N rtes lso indictes tht hying-off ws likely contributing to the lck of grin yield response to incresing N fertiliztion in the summit position (Fig. 2.4c). In the summit, grin protein concentrtion rnged from 76 to 146 g kg -1 with n verge of 113 g kg -1 (Tble 2.2). Greter SPM ws chieved in the summit nd grin protein concentrtion incresed bove the mrket preference of 105 g kg -1 s SPM incresed. In the third study of 2010, there ws significnt qudrtic grin yield response to incresing NR in the south bckslope nd lck of yield response to NR in the north nd summit lndscpe positions (Fig. 2.5, Appendix 4). The yield response in the south bckslope ws ssocited with significnt liner increse in grin protein concentrtion, qudrtic response in HI index nd liner decrese in TWT (Fig. 2.5b, 2.5c nd 2.5d). In the south bckslope grin protein concentrtion rnged from 75 to 123 g kg -1, HI from 0.31 to 0.42, nd TWT from 70.6 to 76.4 kg hl -1 (Tble 2.2). Even though there ws no grin yield response to NR, significnt liner increse in grin protein concentrtion nd decrese in HI with incresing NR ws 19

39 observed in the north bckslope while only significnt qudrtic decrese in HI ws observed in the summit (Fig. 2.5b, 2.5c nd 2.5d). The HI rnged from 0.31 to 0.42 nd 0.35 to 0.41 in the north bckslope nd summit, respectively (Tble 2.2). The 2011 hrvest yer ws chrcterized by higher thn verge winter whet yields for the CAF. The men yield over ll tretments for the north bckslope, foot slope, nd south bckslope positions were 6895, 6132, nd 6818 kg h -1, respectively (Tble 2.3). In 2011, where little wter deficit occurred, N ppliction incresed grin yield for ll lndscpe positions (Fig. 2.6, Appendix 5). Nitrogen fertilizer ppliction rte could explin 47, 11, nd 56% of grin yield increse while SPM could explin 48, 38, nd 50% of grin yield increse for the north, footslope, nd south bckslope positions, respectively (Fig. 2.6 nd 2.6e). Incresing the N rte resulted in significnt increses in grin protein concentrtion for ll three lndscpe positions (Fig. 2.6b). In the foot nd south bckslope, incresing the SPM resulted in significnt liner increses in grin protein concentrtion (Fig 2.6f). Hrvest index rnged from 0.40 to 0.51, 0.38 to 0.49 nd 0.41 to 0.50 in the north, foot, nd south slopes, respectively (Tble 2.3). As N rte incresed, significnt qudrtic response nd liner decline in HI ws observed for the north bckslope nd footslope positions, respectively (Fig. 2. 6c). As SPM incresed, there ws significnt liner decline in HI for the north nd footslope nd qudrtic response in the south bckslope (Fig. 2.6g). In the rnge of responses observed, there ws significnt qudrtic TWT response to incresing NR nd SPM in the south bckslope where slight decreses t higher NR nd SPM were observed (Fig. 2.6d nd 2.6h). A liner increse in TWT ws observed with NR in the north bckslope (Fig. 2.6d) nd with SPM in the footslope (Fig. 2.6h). Despite the fvorble 20

40 conditions, some symptoms of hying-off were observed in the south bckslope t the higher N rtes nd higher SPM where TWT showed some decline over the rnge in responses observed (Fig. 2.6d nd 2.6h). Grin yield in the 2012 hrvest yer ppered representtive of norml winter whet yields for the CAF. Grin yields verged 5398, 5735, nd 4417 kg h -1 for the north, foot nd south bckslopes, respectively (Tble 2.3). Significnt qudrtic responses in grin yield were observed with n increse in NR for the north nd south bckslope positions (Fig. 2.7, Appendix 6). There ws liner increse in grin yield with increse in NR for the footslope. As SPM incresed there ws significnt grin yield response for ll three lndscpe positions (Fig. 2.7e). Grin protein concentrtion rnged from 86 to 110-, 71 to 132- nd from 72 to 164 g kg -1 in the north bckslope, footslope, nd south bckslope, respectively (Tble 2.3). There were slight but significnt liner increses in grin protein concentrtion with n increse in NR from 0 to 160 kg h -1 for the north bckslope nd footslope, respectively (Fig. 2.7b). Grin protein concentrtion decresed but then incresed s SPM incresed from 201 to 546, 161 to 632, nd 203 to 523 spike m -2 in the north bckslope, footslope, nd south bckslope, respectively (Fig. 7f). Hrvest index in the north bckslope, footslope, nd south bckslope rnged from 0.40 to 0.50, 0.37 to 0.48 nd 0.28 to 0.48, respectively (Tble 2.3). Hrvest index decresed linerly s NR incresed nd s SPM incresed for the north nd foot slope positions (Fig. 2.7c nd 2.7g). Hrvest index incresed nd then decresed s SPM incresed in the south bckslope. The only tretment effect on TWT ws observed in the south bckslope where TWT significntly decresed from 80.4 to 71.7 kg hl -1 s NR incresed (Tble 2.3 nd Fig. 2.7d). There ws 21

41 evidence of hying-off observed in the rnge of TWT, HI, nd grin protein concentrtion vlues (Tble 2.3) with greter evidence in the footslope nd south bckslope s compred to the north bckslope. Evidence Rting for Assessing the Occurrence of Hying-off An evidence rting for evluting the occurrence of hying-off ws developed using the symptoms of hying-off described by vn Herwrden et l. (1998) nd the significnt liner or qudrtic reltionships between N fertilizer rte or SPM nd grin yield, grin protein concentrtion, HI nd TWT (Figs. 2.5, 2.6 nd 2.7). Evidence of hying-off for this reserch were lck of grin yield response or grin yield decline with incresing NR or SPM tht were ssocited with decrese in HI, decrese in TWT nd increse in grin protein concentrtion (Tble 2.4). For given site yer, ech lndscpe position ws ssigned n evidence rting using scle of low, medium, or high evidence of hying-off with incresing NR nd SPM (Tble 2.4). Low evidence ws lck of or liner increse in yield ccompnied by men TWT 75.2 kg hl -1, HI> 0.40, nd GPR <110 g kg -1 (Tble 2.4). A qudrtic yield response tht leveled off nd/or did not decline tht ws ssocited with men TWT <75.2 kg hl -1, HI<0.40 nd GPR>110 g kg -1 ws considered medium evidence for hying-off. High evidence ws chrcterized by liner or qudrtic yield decline ssocited with TWT <75.2 kg hl -1. A TWT of 75.2 kg hl -1 ws selected for this evidence rting s this vlue represents the cut-off between U.S. whet grde of 2 or greter nd grde 3 or below (Morris, 2004). In 2010, there ws often lck of or declining grin yield response to incresing NR or SPM for the north, south, nd summit lndscpe positions. There ws greter evidence of 22

42 hying-off under incresing NR or SPM under the wether nd high pre-plnt soil inorgnic N conditions of The evidence for hying-off ws rted s medium to high cross ll lndscpe positions (Tble 2.5). This ws especilly true of the south bckslope position where the frequency of high evidence for hying-off ws gretest nd the symptoms of hying-off were most strongly expressed. The south bckslope hd medium to high evidence of hyingoff s NR or SPM incresed (Tble 2.5). The north bckslope hd medium to high evidence of hying-off s SPM incresed nd medium evidence s NR incresed. Under the fvorble wether conditions of the 2011 winter whet crop yer the evidence of hying-off s result of incresing NR or SPM ws low cross ll lndscpe positions (Tble 2.6). There ppered to be sufficient vilble wter to support both vegettive growth nd grin filling. The 2012 hrvest yer ws considered to be representtive of the growing conditions experienced in most yers. The evidence rting for hying-off ws low to medium in the 2012 winter whet hrvest yer (Tble 2.6). Incresing the NR in the south bckslope resulted in medium evidence for hying-off from observed symptomology in the rnge of TWT, HI, nd grin protein vlues (Tble 2.6). Incresing the SPM ppered to contribute to medium evidence rting for hying-off in both the footslope nd south bckslope in The north bckslope hd low evidence of hying-off s consequence of incresing either NR or SPM (Tble 2.6). Reltionship of Kernel Mss to Test Weight The reltionship between TWT nd kernel mss (KM) ws investigted to evlute if TWT s symptom of hying-off hs strong reltionship to KM cross site yers where 23

43 different conditions previled. There ws significnt qudrtic reltionship between KM nd TWT in 2010 nd 2012 but not in 2011 (Fig. 2.8). The qudrtic reltionship ws similr cross ll lndscpe positions in 2010 (Fig. 2.8). In 2012 there ws some seprtion in the reltionship between KM nd TWT for the footslope position s compred to the north nd south bckslopes (Fig. 2.8c). In 2011, there were lrge rnges in TWT for ny given KM (Fig. 2.8b). Test weight vlues were reltively high in 2011 s compred to 2010 nd 2012 nd the mjority of TWT vlues in 2011 were bove the 75.3 or 76.7 kg hl -1 minimum for U.S. whet grde of 2 or 1, respectively (Fig. 2.8b). A mjority of test weight vlues in 2010 were below the minimum requirement to qulify for grde of 2 or higher (Fig. 2.8). DISCUSSION Does incresing NR nd SPM led to hying-off in dry versus wet conditions? The combintion of incresed erly growth due to higher SPM nd/or N fertiliztion rtes in drier yers or lndscpe positions were expected to increse the occurrence of hyingoff. Greter evidence of hying-off ws observed with incresing NR nd SPM under the dry conditions nd high pre-plnt soil inorgnic N conditions of As hypothesized, the symptoms of hying-off were most expressed in the south bckslope nd summit lndscpe positions tht exhibited less vilble wter t tillering nd nthesis s compred to the north nd footslope lndscpe positions. High residul N, especilly in the summit position, coupled with drier thn norml conditions in 2010 likely contributed to the greter incidence of hyingoff s compred to the other site yers. The evidence of hying-off observed in the south bckslope under the more typicl precipittion levels of 2012 indictes tht hying-off cn lso 24

44 occur under reltively norml precipittion yers in drier lndscpe positions. Root restrictive lyers in the south bckslope nd summit lndscpe positions my lso contribute to hying-off by preventing ccessibility to deeper wter nd nutrient resources s previously observed by Pn nd Hopkins (1991). This is supported by evidence of hying-off observed in the drier south bckslope lndscpe positions even in the reltively wet conditions of Hying-off in response to NR nd SPM is not observed in wet conditions due to greter vilble wter. Evidence of hying-off ws not observed with incresing NR or SPM in the north bckslopes in 2011 nd 2012 where greter vilble wter ws observed compred to the south bckslope. There ws some evidence of hying-off with incresing SPM in the footslope of 2012 which ws not expected due to the high vilble wter content. This my be ttributed to rpid vegettive growth in the spring stimulted by high vilble wter nd N supply in the footslope lndscpe position s compred to the other lndscpe positions. The footslope position hd 1,467 nd 2,878 kg greter biomss h -1 compred to the north nd south bckslopes (dt not shown) coinciding with lower vilble wter t mturity s compred to the north bckslope. Erly seson vegettive growth in the 2012 footslope ppers to hve set n unrelisticlly high yield resulting in mngement induced wter deficit t grin filling. There ws evidence of bedrock in the 120 to 150-cm depth increment during soil smpling events indicting tht the mount of vilble wter nd reltively shllow soil my hve lso contributed to hying-off in the footslope position in Identifying symptoms to provide evidence of hying-off. 25

45 A declining HI indictes when yield is disproportiontely low reltive to the totl dry mtter production (vn Herwrden et l., 1998). Across site yers nd lndscpes, HI ws observed to decline with incresing NR nd SPM with few exceptions. This indictes tht HI response trend to NR or SPM lone would not be good indictor of hying-off. Using HI threshold of 0.40, however, did pper to be good indictor of hying-off. In this study, grin yield nd TWT response were found to be better predictors of hying-off while hrvest index nd grin protein concentrtion provided dditionl symptomology to more clerly identify the occurrence. Test weight declines coupled with continued grin yield increses s NR or SPM incresed provide evidence tht hying-off my be expressed in TWT vlues before it is observed in grin yield. In the U.S., TWT is used s n estimte of the plumpness of whet kernels (i.e., kernel mss) nd is n importnt grde determining fctor impcting the price received by producers (Morris, 2004). Minimum test weights of 76.7, 75.3, 72.9, 70.3, nd 66.3 kg hl -1 re required for U.S. grdes 1, 2, 3, 4, nd 5, respectively (Morris, 2004). In this study, KM ws found to be significntly relted to TWT but only in norml to dry yers where evidence of hying-off ws observed (i.e., 2010 nd 2012). vn Herwrden et l. (1998) proposed tht KM below 25- nd 30-mg indicte hying-off more certinly nd probbly occurred for whet tht generlly produces kernel mss of 40 mg. Vribility in conditions nd crop response to NR nd SPM mong yers nd lndscpes observed in this study nd others (Cih, 1983; Fiez et l., 1994b) supports the need to further develop evidence of hying-off tht cn be prescriptive without the time nd expense of NR nd SPM trils. Fiez et l., (1994b) noted tht KM declined with 26

46 incresing N rte nd tended to be lowest t the shoulder lndscpe position. More clerly defined evidence of hying-off using yield components, such s KM vlues used by vn Herwrden et l. (1998), under the rnges in lndscpe specific environments nd climte conditions is needed to provide useful nd rpid ssessment for reserchers, breeders, nd growers. Given the lck of precipittion during nd fter nthesis in Plouse drylnd cropping systems, it will be prticulrly importnt to consider lndscpe specific seeding rte influences on spike popultions nd compenstion mong yield components in conjunction with vrible rte N mngement. In ll yers, it ws observed tht SPM ws better predictor of yield response (i.e., higher r 2 ) thn ctul plnt popultion (dt not shown) s reported previously (Bssinette, 1995; Fiez et l., 1994b). The seeding rte tretments were designed to mnipulte the production nd survivl of winter whet tillers nd provide rnge in the number of SPM mong different lndscpe positions. Mnging for optimum SPM will require knowledge of the tillering chrcteristics of specific crop under given frm mngement systems nd environmentl conditions. Profuse tillering my result in too mny SPM nd ccumultion of greter vegettive biomss thn cn be supported. Conversely, suboptiml SPM from mngement, environmentl, or genetic fctors cn limit the bility of whet crop to compenste for reduced plnt popultion (Drwinkle, 1978; Cih, 1984). In ddition to the lck of yield gin from dded N, grin protein concentrtions in the driest yer where hying-off ws most observed were bove the mrket clss demnd of 105 g kg -1. Mull et l. (1992) reported tht prts of the lndscpe with the lowest vilble wter 27

47 content in the profile hd the highest grin protein concentrtions due to wter stress-nitrogen interctions. Nitrogen fertilizer rtes bove the yield gol therefore presents risk for not only hying-off but excess grin protein concentrtions nd the potentil for N loss to unintended portions of the ecosystem (vn Herwrden et l., 1998; Angus nd vn Herwrden, 2001). This reserch indictes tht site-specific N nd seed rte mngement will be importnt for optimizing grin yield, yield qulity, nd reducing the risk of hying-off in drier lndscpe positions. Adopting vrible rte N nd seed mngement will require better understnding of the temporl nd sptil vribility in lndscpe specific processes influencing the reltionship between crop growth, nutrient nd wter use efficiencies, nd grin yield nd qulity. For exmple, rpid in-crop ssessments of biomss nd crop N sttus using trctor mountble remote sensing equipment such s LiDAR (Eitel et l., 2014) could be linked with post-mortem yield, HI, TWT, nd nitrogen use efficiency dt by mngement zones nd/or lndscpe positions. Furthermore, trctor mounted LiDAR estimtes of biomss could be coupled with on-combine grin protein sensors nd grin yield monitors to estimte HI on site-specific bsis. CONCLUSIONS Mnging to llow for yield component compenstion without contributing to hyingoff should id trgeting of optimum combintions of N nd seed rte for the driest lndscpe positions tht lso support economicl yields, pproprite grin protein concentrtions, nd TWT vlues to chieve high whet grdes. Grin yield, protein concentrtion, HI nd TWT response to incresing NR nd SPM vried by yer nd lndscpe. These symptoms of hying- 28

48 off indicted tht there is medium evidence for hying-off in the drier south bckslope nd summit lndscpe positions s NR nd SPM increse nd tht hying-off likely occurs in most yers for these lndscpe positions. Medium to high evidence for hying-off s NR nd SPM incresed ws observed cross ll lndscpe positions studied in dry yers. This reserch indicted tht drier lndscpe positions nd drier yers could be N fertilized nd seeded t lower rtes thn wetter lndscpe positions or wetter yers to optimize yield nd void mngement induced hying-off. Site-specific N by seed rte mngement should consider split-n pplictions to djust N ppliction rtes to growing seson conditions nd seeding rtes nd row spcing tht consider environmentl controls on crop growth nd compenstion mong yield components. For this strtegy to be successful, use nd breeding of vrieties for reduced tillering is needed. Additionl reserch to ssess the risk or occurrence of hying off, given n inbility to predict growing seson precipittion t the time of winter whet plnting, is needed. Evidence of hying-off in the Plouse could be better dignosed with dditionl reserch on crop response to mngement by environment reltionships. Additionl spects to consider include remote sensing of whet biomss nd biomss N sttus t nthesis, impct of nthesis biomss on vilbility of soil wter nd mobiliztion of ssimiltes going into grin filling, nd the rnge of conditions where N fertiliztion contributes to hying-off. 29

49 REFERENCES CITED Ali, A., M.A. Choudhry, M.A. Mlik. R. Ahmd nd Sifulh Efect of vrious doses of nitrogen on the growth nd yield of two whet cultivr. Pk. J. Biol. Sci., 3(6): Angus, J.F. nd A.F. vnherwrden Incresing wter use nd wter use efficiency in drylnd whet. Agron. J. 93: Bssinette, J.P Plnting dte, cultivr nd seeding rte effects on winter whet, spring whet nd spring brley gronomic performnce nd decision to replnt. University of Idho Msters Thesis. Brown, P.L Wter use nd soil wter depletion by drylnd winter whet s ffected by nitrogen fertiliztion. Agron. J. 63: Bulmn, P. nd L.A. Hunt Reltionship mong tillering, spike number nd grin yield in winter whet (Triticum estivum L.) in Ontrio. Cn. J. Plnt Sci. 68: Buscc nd Montgomery, Buscc, A.J., nd J.A. Montgomery Field-lndscpe vrition in soil physicl properties of the Northwest drylnd crop production region. In: Veseth, R. nd B. Miller (eds.), Precision Frming for Profit nd Conservtion. 10th Inlnd Northwest Conservtion Frming Conference Proceedings, Wshington Stte University, Pullmn. Cih, A.J Seeding rte nd seeding dte effects on spring seeded smll grin cultivrs. Agron. J. 75: Cih, A.J Slope position nd grin yield of soft white winter whet. Agron. J. 76: Drwinkle, A Ptterns of tillering nd grin production of winter whet t wide rnge of plnt densities. Neth. J. Agric. Sci. 26: Donldson. E., W.F. Schillinger, nd S.M. Dofing Strw production nd grin yield reltionships in winter whet. Crop Sci. 41: Eitel, J.U.H., T.S. Mgney, L.A. Vierling, T.T. Brown, nd D.R. Huggins. LiDAR bsed biomss nd crop nitrogen estimtes for rpid, non-destructive ssessment of whet nitrogen sttus. Field Crops Res. 159: Entz nd Fowler, Influence of crop nd wter environment nd dry mtter ccumultion on grin yield of no-till winter whet. Cn. J. Plnt Sci. 69:

50 Fiez. T.E., B.C. Miller, nd W.L. Pn Assessment of sptilly vrible nitrogen fertilizer mngement in winter whet. J. Prod. Agric. 7(1): Fiez, T.E., B.C. Miller, nd W.L. Pn. 1994b. Winter whet yield nd grin protein cross vried lndscpe positions. Agron. J. 86: Fiez, T.E., W.L. Pn, nd B.C. Miller Nitrogen use efficiency of winter whet mong lndscpe positions. Soil Sci Soc. Am. J. 59: Fiez, T. E. nd B.C. Miller Vrying winter whet seeding rtes mong lndscpe positions. J. Production Aric. 8: Fischer, R.A. nd G.D. Kohn The reltionship of grin yield to vegettive growth nd postflowering lef re in the whet crop under conditions of limited soil moisture. Aust. J. Agric. Res. 17: Fuentes, J.P Influence of tillge on soil properties under griculturl nd nturl pririe systems. Grci del Morl, L.F., Y.Rhrrbti, D. Villegs nd C. Royo Evlution of grin yield nd its components in durum whet under Meditternen conditions: n ontogenic pproch. Agron. J. 95: Hll, G.F. nd C.G. Olson Predicting vribility of soils from lndscpe models. In M.J. Musbch nd L.P. Wilding (eds) Sptil vribilities of soils nd lndforms. SSSA Specil Publiction no. 28. pge 10 (9-24). Hne, D.C. nd F.V. Pumphrey Crop wter use curves for irrigtion scheduling. Oregon Stte University Agriculture Experiment Sttion Specil Report 706. Corvllis, OR. Htfield, J.L., T.J. Suer, nd J.H. Prueger Mnging soils to chieve greter wter use efficiency: review. Agron. J. 93: Hy, R.K Hrvest index: review of its use in plnt breeding nd crop physiology. Ann. Appl. Biol. 126: Hermnson, R., W. Pn, C. Perillo, R. Stevens, C. Stockle. Nitrogen use by crops nd the fte of Nitrogen in the soil nd vdose zone. Wshington Stte University nd Wshington Deprtment of Ecology. Publiction No Holen, D.L., P.L Bruckner, J.M. Mrtin, G. R. Crlson, D.M. Wichmn, nd J. E. Berg Response of winter whet to simulted stnd reduction. Agron. J. 93:

51 Huggins, D.H Site-specific N mngement for direct-seed cropping systems. Chpter 16 In Kruger, C., G. Yorgey, S. Chen, H. Collins, C. Feise, C. Frer, D. Grntstein, S. Higgins, D. Huggins, C. McConnell, K. Pinter, C. Stöckle Climte Friendly Frming: Improving the Crbon Footprint of Agriculture in the Pcific Northwest. CSANR Reserch Report Wshington Stte University: Friendly-Frming-Finl-Report/. Huggins, D.H. nd D. P. Uberug Field heterogeneity of soil orgnic crbon nd reltionships to soil properties nd terrin ttributes. Chpter 14 In Kruger, C., G. Yorgey, S. Chen, H. Collins, C. Feise, C. Frer, D. Grntstein, S. Higgins, D. Huggins, C. McConnell, K. Pinter, C. Stöckle Climte Friendly Frming: Improving the Crbon Footprint of Agriculture in the Pcific Northwest. CSANR Reserch Report Wshington Stte University: Frming-Finl-Report/. Ibrhim, H.M. nd D.R, Huggins Sptio-temporl ptterns of soil wter storge under drylnd griculture t the wtershed scle. Journl of Hydrology. 404: Joseph, K.D.S.M, M.M. Alley, D.E. Brnn, nd W.D. Grvelle Row spcing nd seeding rte effects on yield nd yield components of soft red winter whet. Agron. J. 77: Krow, R.S., E.L. Klepper, R.W. Rickmn, nd T.R. Toll Erly growth nd development of cerels. EM Klepper, B., R.W. Rickmn, nd C.M. Peterson Quntittive chrcteriztion of vegettive development in smll cerel grins. Agron. J. 74: Leggett, G.E Reltionships between whet yield, vilble moisture nd vilble nitrogen in estern Wshington dry lnd res. Wshington Agric. Exp. Stn. Bull. 609, Pullmn. Mhler, R.L., D.F. Bezdicek, nd R.E. Witters Influence of slope position on nitrogen fixtion nd yield of dry pes. Agron. J. 71: Morris, C.F Grin qulity Idho whet production guide. Pg In L.D. Robertson, S.O. Guy, nd B.D. Brown (Eds.) Southern Idho Drylnd Winter Whet Guide. University of Idho BUL 827. Mull, D.J., A.U. Bhtti, M.W. Hmmond, nd J.A. Benson A comprison of winter whet yield nd qulity under uniform versus sptilly vrible fertilizer mngement. Agric. Ecosystems Environ. 38:

52 Pn, W.L. nd A.G. Hopkins Plnt development, nd N nd P use of winter brley. I. Evidence of wter stress-induced P deficiency in n eroded toposequence. Plnt nd Soil 135:9-19. Pn, W.L., W. Schillinger, D. Huggins, R. Koenig, nd J. Burns Fifty yers of predicting whet nitrogen requirements in the Pcific Northwest U.S.A. Pwson, W.W., O.L. Brough, J.P. Swnson, nd G. M. Horner Economics of cropping systems nd soil conservtion in the Plouse. Schillinger, W.F Tillge method nd sowing rte reltions for drylnd spring whet, brley, nd ot. Crop Sci. 45: Schillinger, W.F. nd R.I. Ppendick Then nd now: 125 yers of drylnd whet frming in the Inlnd Pcific Northwest. Agron. J. 100: Schillinger, W.F., S.E. Schofstoll, nd J. R. Alldredge Avilble wter nd whet grin yield reltions in Mediterrnen climte. Field Crops Reserch. 109: Soil Survey Stff, Nturl Resources Conservtion Service, United Sttes Deprtment of Agriculture. Web Soil Survey. Avilble online t Accessed [05/15/2010]. Sowers, K.E., B.C. Miller, W.L. Pn. 1994b. Optimizing yield nd grin protein in soft white winter whet with split nitrogen pplictions. Agron. J. 86: Tompkins, D.K., G.E. Hultgreen, A.T. Wright, nd D.B. Fowler Seed rte nd row spcing of no-till winter whet. Agron. J. 83: Vn Herwrden, A.F., G.D. Frquhr, J.F. Angus, R.A. Richrds, nd G.N. Howe Hyingoff, the negtive grin yield response of drylnd whet to nitrogen fertilizer I. Biomss, grin yield, nd wter use. Aust. J. Agric. Res. 49: Vn Herwrden, A.F., J.F. Angus, R.A. Richrds, nd G.D. Frquhr. 1998b. Hying-off, the negtive grin yield response of drylnd whet to nitrogen fertilizer I. Crbohydrte nd protein dynmics. Aust. J. Agric. Res. 49:

53 Tble 2.1. Lndscpe position chrcteristics for N fertiliztion rte by winter whet seeding rte experiments conducted t the Cook Agronomy Frm during , nd crop yers. Site Yer Lndscpe Position Soil Series Pre-Plnt Soil Inorgnic N Non fertilizer N Contributions Avilble Soil Wter in Spring N Supply kg N h cm North Bckslope Plouse SiL c 222 b 19 Summit Nff SiL b 16 b South Bckslope Plouse SiL b b North Bckslope Plouse SiL 59 b b Footslope Thtun SiL b South Bckslope Plouse SiL 56 b b 39 b 2012 North Bckslope Plouse SiL 66 b b 39 b Footslope Thtun SiL 59 b South Bckslope Plouse SiL b c Soil inorgnic N nd vilble soil wter were summed over soil profile smples collected t 30-cm increments from 0- to 150-cm depth in the fll for pre-plnt nd t tillering for spring vilble wter. Clculted s N minerliztion following (Huggins nd Pn, 2003) but this vlue likely includes redistribution nd losses of inorgnic N nd should therefore be considered non-fertilizer N contributions. Pre-plnt inorgnic N estimted from control plots (0 kg N h -1 ) of spring soil smples due to lck of preplnt soil smpling in the fll of Within columns, mens followed by the sme letter re not significntly different t the 10% level. 34

54 Tble 2.2. Mens nd rnges for vrible relted to hying off nd crop growth for the three studies of the 2010 site yer. Study Mens nd Rnges by Lndscpe Vrible North South Summit Men Rnge Men Rnge Men Rnge 1: Plnt Density Experiment with Uniform N APD, plnts m n.. n.. SPM, spikes m n.. n.. KPS, kernels spike n.. n.. KM, mg n.. n.. Grin Yield, kg h n.. n.. Grin Protein, g kg n.. n.. HI, kg grin (kg biomss) n.. n.. TWT, kg hl n.. n.. Mv, cm n.. n.. 2: Nitrogen Rte X Plnt Density Experiment NR, kg h -1 n.. n APD, plnts m -2 n.. n SPM, spikes m -2 n.. n KPS, kernels spike -1 n.. n KM, mg n.. n Grin Yield, kg h -1 n.. n Grin Protein, g kg -1 n.. n HI, kg grin (kg biomss) -1 n.. n TWT, kg hl -1 n.. n Mv, cm n.. n : Nitrogen Rte Experiment with Uniform Seeding Rte NR, kg h SPM, spikes m KPS, kernels spike KM, mg Grin Yield, kg h Grin Protein, g kg HI, kg grin (kg biomss) TWT, kg hl Mv, cm Abbrevitions for vribles: NR, Nitrogen fertilizer rte; APD, ctul plnt density ; SPM, spike density; KPS, kernels per spike; KM, kernel mss; HI, hrvest index; TWT, test weight; TMCWU, consumptive wter use between tillering nd mturity ; WUE, wter use efficiency ; Mv, vilble wter t mturity. n.. not pplicble. 35

55 Tble 2.3. Mens nd rnges for vrible relted to hying off nd crop growth for the 2011 nd 2012 site yers. Yer Mens nd Rnges by Lndscpe Vrible North Footslope South Men Rnge Men Rnge Men Rnge 2011 NR, kg h APD, plnts m SPM, spikes m KPS, kernels spike KM, mg Grin Yield, kg h Grin Protein, g kg HI, kg grin kg biomss TWT, kg hl Tv, cm Av, cm Mv, cm NR, kg h APD, plnts m SPM, spikes m KPS, kernels spike KM, mg Grin Yield, kg h Grin Protein, g kg HI, kg grin (kg biomss) TWT, kg hl Tv, cm Av, cm Mv, cm Abbrevitions for vribles: NR, Nitrogen fertilizer rte; APD, ctul plnt density ; SPM, spike density; KPS, kernels per spike; KM, kernel mss; HI, hrvest index; TWT, test weight; Tv, vilble wter t tillering; Av, vilble wter t nthesis; Mv, vilble wter t mturity. 36

56 Tble 2.4. Criteri for evluting the evidence of hying-off using yield, test weight, hrvest index, nd grin protein concentrtion response to incresing N rte or SPM from regression nlysis. Grin Yield Response Test Weight Hrvest Index No response or liner increse Grin Protein Conc. kg hl -1 g kg -1 Evidence Rting TWT 75.2 HI<0.40 GPR>110 MED Other LOW Qudrtic Response tht levels off nd does not decline TWT 75.2 HI<0.40 GPR>110 MED Other LOW Decline (liner or qudrtic) TWT>75.3 MED TWT 75.2 HIGH Evidence of hying off combined the results of regression nlysis for response of grin yield, grin protein concentrtion, hrvest index (HI), test weight (TWT) to incresing N rte or SPM. Only liner or qudrtic trends were tested for significnce t the 10% level. Lck of yield response occurred if there ws no significnt liner or qudrtic response. 37

57 Tble 2.5. Hying off symptomology nd evidence rting for the 2010 site yer. Study Tretment Lndscpe Grin Yield Response Test weight Hrvest Index Grin Protein Rnge kg hl -1 g kg -1 Evidence Rting 1: Plnt Density Experiment with Uniform N Plnt Density NBS No Response MED SBS Decline, Liner HIGH 2: Nitrogen Rte X Plnt Density Experiment Nitrogen Rte SBS No Response MED SU No Response MED Plnt Density SBS No Response MED SU No Response MED 3: Nitrogen Rte Experiment with Uniform Seeding Rte Nitrogen Rte NBS No Response MED SBS Qudrtic, Declines HIGH SU No Response MED Lndscpe positions re bbrevited s NBS, north bckslope; SBS, south bckslope; SU, summit. 38

58 Tble 2.6. Hying off symptomology nd evidence rting for 2011 nd 2012 site yers. Yer 2011 Tretment Lndscpe Yield Test Weight Hrvest Index Grin Protein Rnge kg h -1 kg hl -1 g kg -1 Evidence Rting Nitrogen Rte NBS Liner LOW FS Liner LOW SBS Liner LOW Spike Density NBS Liner LOW FS Liner LOW SBS Qudrtic, Levels off LOW 2012 Nitrogen Rte NBS Qudrtic, No Decline LOW FS Liner LOW SBS Qud, Levels off MED Spike Density NBS Qud, No Decline LOW FS Qud, Levels off MED SBS Liner MED Lndscpe positions re bbrevited s NBS, north bckslope; SBS, south bckslope; FS, footslope. 39

59 70 Cumultive Precipittion, cm D Month Grph 6 Norml b Growing Degree Dys, 32 degrees C Bse Temperture /1/09 3/1/10 9/1/10 3/1/11 9/1/11 3/1/12 9/1/12 Month nd Yer Norml Monthly Oct to Sept Figure 2.1. Cumultive precipittion () nd growing degree dys (b). Cumultive precipittion compred to norml precipittion ( ) for Oct. 1 to Sept. 30 using NOAA Ntionl Wether Service Pullmn 2 NW (46 46 N, W) locted t the Plouse Field Conservtion Field sttion, ner Pullmn, WA. Avilble wter included soil vilble wter plus precipittion. Cumultive growing degree dys clculted s (Tmx+Tmin)/2 using bse temperture of 0 C. 40

60 Avilble Wter, cm Avilble Wter, cm b b b b b b c North bckslope South bckslope Summit North bckslope Footslope South bckslope b b b 2012 Avilble Wter, cm c b c b c North bckslope Footslope South bckslope b c 0 Apr My Jun Jul Aug Sep Oct Nov Month Figure 2.2. Avilble wter in the 150-cm soil profile during the winter whet growing seson for 2010 (), 2011 (b) nd 2012 (c) winter whet hrvest yers. Soil vilble wter ws determined on soil smples collected from 0 to 150-cm t tillering, nthesis, nd mturity. Within dte, mens followed by the sme letter re not significntly different t the 10% level using proc mixed (SAS 9.4, SAS Inst., 2012). 41

61 Grin Yield, kg h Adj. r 2 NBS = n SBS = 0.44 SBS Grin Protein, g kg b c Adj. r 2 NBS = n SBS = 0.32 SBS 0.36 Hrvest Index SBS Test Weight, kg hl Adj. r 2 NBS = n SBS = 0.26 d Adj. r 2 NBS = 0.11 SBS = Spikes m-2 South Bckslope North Bckslope Figure 2.3. Regression trends in grin yield (), grin protein concentrtion (b), hrvest index (c) nd test weight (d) in response to incresing SPM for the 2010 Plnt Density Experiment with Uniform N (i.e., Study 1). Only liner or qudrtic trends were tested nd only those tht were significnt t the 10% level re shown with lndscpe positions bbrevited s NBS, north bckslope nd SBS, south bckslope. Non-significnt indicted by n indictes not pplicble. 42

62 e Grin Yield, kg h Grin Yield, kg h SPM vs GW1-3 SPM vs GW1-4 u sbs su Hrvest Index Grin protein, g kg -1 Test Weight, kg hl b c d Adj. r 2 SBS = 0.60 SU = n Adj. r 2 SBS = 0.45 SU = 0.14 Adj. r 2 SBS = n SU = Grin protein, g kg -1 Hrvest Index Test Weight, kg hl f g h Adj. r 2 SBS = 0.31 SU = 0.62 Adj. r 2 SBS = 0.42 SU = n sbs SPM vs TWT1-3 SPM vs TWT1-4 N Fertilizer Rte, kg h -1 South Bckslope Summit Spikes m -2 Figure 2.4. Regression trends in grin yield (), grin protein concentrtion (b), hrvest index (c) nd test weight (d) in response to incresing SPM for the 2010 Nitrogen Rte X Plnt Density Experiment (i.e., Study 2). Only liner or qudrtic trends were tested nd only those tht were significnt t the 10% level re shown with lndscpe positions bbrevited s SBS, south bckslope (drk circles) nd SU, summit (open circles). Non-significnt indicted by n indictes not pplicble. 43

63 Grin Yield, kg h -1 Grin Protein Conc., g kg b c Adj. r 2 NBS = n SBS = 0.18 SU = n Adj. r 2 NBS = 0.26 SBS = 0.67 SU = n sbs nbs sbs 0.40 Hrvest Index Test Weight, kg hl Adj. r 2 NBS = 0.12 SBS = 0.51 SU = 0.40 d Adj. r 2 NBS = n SBS = 0.15 SU = n North Bckslope South Bckslope Summit sbs N Fertilizer Rte, kg h -1 Figure 2.5. Regression trends in grin yield (), grin protein concentrtion (b), hrvest index (c) nd test weight (d) in response to incresing SPM for the 2010 Nitrogen Rte Experiment with Uniform Seeding Rte (i.e., Study 3). Only liner or qudrtic trends were tested nd only those tht were significnt t the 10% level re shown with lndscpe positions bbrevited s NBS, north bckslope; SBS, south bckslope; nd SU, summit. Non-significnt indicted by n indictes not pplicble. 44

64 e th tslope th Bckslope h Bckslope slope Hrvest Index Grin Protein, g kg -1 Grin Yield, kg h b c Adj. r 2 NBS = 0.12 FS = 0.06 SBS = n d NR X Dt X Dt Adj. r 2 NBS = 0.47 FS = 0.13 SBS = 0.56 Adj. r 2 NBS = 0.33 FS = 0.14 SBS = 0.56 Hrvest Index Grin Protein, g kg -1 Grin Yield, kg h f g Adj. r 2 NBS = 0.12 FS = 0.07 SBS = 0.13 h NR X Dt X Dt Adj. r 2 NBS = 0.48 FS = 0.38 SBS = 0.50 Adj. r 2 NBS = n FS = 0.09 SBS = 0.09 North bckslope Footslope South bckslope Foot slope South North Foot South th bckslope th bckslope Test Weight, kg hl Adj. r 2 NBS = 0.04 FS = n SBS = Test Weight, kg hl Adj. r 2 NBS = n 75 FS = 0.21 SBS = Foot South N Fertilizer Rte, kg h -1 North Footslope South Figure 2.6. Regression trends in grin yield ( nd e), grin protein concentrtion (b nd f), hrvest index (c nd g) nd test weight (d nd h) in response to incresing NR nd SPM for Only liner or qudrtic trends were tested nd only those tht were significnt t the 10% level re shown with lndscpe positions bbrevited s NBS, north bckslope; SBS, south bckslope; nd FS, footslope. Nonsignificnt indicted by n indictes not pplicble. Spikes m -2 45

65 e north foot Grin Yield, kg h-1 Grin Protein, g kg b c X Dt X Dt Adj. r 2 NBS = 0.70 FS = 0.06 SBS = 0.28 Adj. r 2 NBS = 0.16 FS = 0.06 SBS = n Grin Yield, kg h-1 Grin Protein, g kg f g X Dt X Dt Adj. r 2 NBS = 0.54 FS = 0.62 SBS = 0.46 Adj. r 2 NBS = 0.07 FS = 0.37 SBS = 0.06 north foot south north foot south north foot south Hrvest Index Test Weight, kg hl Adj. r 2 NBS = 0.56 FS = 0.03 SBS = n d Adj. r 2 NBS = n FS = n SBS = 0.21 X Dt N Fertilizer Rte, kg h-1 Hrvest Index Test Weight, kg hl h North Bckslope Footslope South Bckslope X Dt 74 Adj. r 2 NBS = n 72 FS = n SBS = n Spikes m-2 Adj. r 2 NBS = 0.47 FS = 0.11 SBS = 0.11 north foot south SPM vs TWT1-1 SPM vs TWT1-2 SPM vs TWT1-3 Figure 2.7. Regression trends in grin yield ( nd e), grin protein concentrtion (b nd f), hrvest index (c nd g) nd test weight (d nd h) in response to incresing NR nd SPM for Only liner or qudrtic trends were tested nd only those tht were significnt t the 10% level re shown with lndscpe positions bbrevited s NBS, north bckslope (blck circles); SBS, south bckslope (blck tringle); nd FS, footslope (open circles). Non-significnt indicted by n indictes not pplicble. 46

66 80 North Bckslope South Bckslope Summit Adj r2 = 0.65 Test Weight, kg hl y = X -0.05X 2 84 b 82 Test Weight, kg hl Test Weight, kg hl North Bckslope Footslope South Bckslope Adj r2 = 0.50 North bckslope Footslope South bckslope c 70 y = X X Kernel Mss, mg Figure 2.8. Reltionship between kernel mss nd test weight for 2010 (), 2011 (b), nd 2012 (c) cross ll tretments. Regression line nd djusted r 2 shown where significnt liner or qudrtic trends t the 10% level were observed. 47

67 CHAPTER THREE IMPROVING NITROGEN USE EFFICIENCY OF WINTER WHEAT: THE ROLE OF LANDSCAPE, NITROGEN, AND SEEDING RATE ABSTRACT Improving nitrogen use efficiency (NUE) in drylnd cropping systems is complicted by wter-n-yield interctions tht exhibit considerble sptil nd temporl vribility cross lndscpes typicl of the Plouse region. The objectives of this reserch were to evlute the impct of N by seed rte tretments on NUE (defined s grin yield divided by N supply) nd vilble soil wter depletion mong three different lndscpe positions. N fertilizer rte (0 up to 160 kg h -1 ) by seeding rte (98 up to 335 seeds m -2 ) plot trils were employed cross three different lndscpe positions (north bckslope, footslope, south bckslope, or summit) in 2010, 2011, nd Anlysis of vrince ws used to determine tretment impcts on NUE nd relted soil nd plnt physiology bsed components. Incresing the N fertilizer rte (NR) from 0 to 160 kg N h -1 resulted in nthesis biomss increses of up to 34 to 50%, 31 to 20%, nd 30 to 35% in the north, foot, nd south bckslopes in 2011 nd 2012, respectively. Nitrogen fertilizer induced increses in nthesis biomss were ssocited with greter depletion of vilble wter in the soil surfce (0 to 90 cm) for the north nd south bckslope positions, but not the footslope. In both 2011 nd 2012, the effect of seeding rte (SR) on biomss nd vilble wter ws not s gret s tht of NR nd there were no significnt differences in nthesis biomss mong the 165, 250, nd 335 seeds m -2 tretments for ll lndscpe positions. Nitrogen use efficiency decresed by 15, 18 to 22 nd 19 to 14 kg kg -1 s N rte incresed from 0 to 160 kg N h -1 for the north, footslope nd south bckslope for 2011 nd 2012, respectively. Seeding rte generlly incresed NUE, by s much s 11 kg kg -1 in the 2011 north bckslope, but 48

68 the effects were miniml. Nitrogen losses to competing pthwys limited crop N uptke nd contributed to the low NUE s observed. Nitrogen use efficiency trgets could be chieved with lower NR in dry yers nd especilly in drier lndscpes under dry wether conditions. Trget NUE nd optimum nthesis biomss could be chieved with 34 to 68% reduction in typicl seeding rtes used t the Cook Agronomy Frm. Improving crop yield nd N mngement under drylnd crop production will continue to require simultneous understnding of soil wter nd N dynmics. INTRODUCTION Improving the efficiency with which nitrogen (N) fertilizers re used in cropping systems hs the potentil to ddress environmentl concerns while lso providing economic benefit to griculturl producers (Fiez et l., 1995; Huggins, 2010; Robertson nd Vitosek, 2009). For exmple, cropping systems tht reduce N fertilizer inputs by incresing nitrogen use efficiency (NUE) cn reduce costs ssocited with N fertilizer inputs nd minimize off site impcts ssocited with nitrte contmintion of qutic systems (Huggins nd Pn, 1993; Keller et l., 2008) nd emissions of greenhouse gsses to the tmosphere (Robertson nd Vitousek., 2009). Regionl, if not field scle, evlutions of NUE re needed to develop meningful strtegies to improve NUE given the strong influence of environmentl conditions on the mount nd timing of N vilbility, crop N uptke, nd N losses (Cssmn, 1999; Dobermn, 2007; Huggins et l., 2010). Nitrogen use efficiency nd the fte of N in the soilplnt system is further complicted by the interction of wether, soil properties, nd cropping system mngement prctices (Cssmn et l., 2002; Fuentes et l., 2003; Huggins nd Pn, 49

69 2003; Dobermn, 2005). Becuse of this, site-specific N fertilizer mngement (otherwise known s vrible rte) is considered one of the most prcticl strtegies for improving griculturl NUE nd reducing N loss to unintended portions of the environment (Cssmn et l., 2002; Robertson nd Vitousek, 2009). Environmentl fctors most relted to NUE include vilbility of the N supply, soil temperture, timing nd mount of precipittion, mount of growing seson vilble soil wter, nd vrious dditionl soil properties (Dobermn, 2007; Hwkesford, 2012). There is considerble sptil nd temporl vribility in these fctors in the Plouse region (Huggins et l., 2010). Nitrogen supply s well s storge nd vilbility of wter re importnt determinnts of grin yield nd subsequently NUE in drylnd cropping systems of the Plouse region (Leggett, 1960; Pn et l., 2007). For exmple, Huggins et l. (2010) estimted N minerliztion, n importnt contribution to the N supply, to rnge from 20 to 70 kg N h -1 over 12 h field. Wter-N-yield interctions re importnt in determining the site-specific N supply nd N fertilizer requirements under drylnd whet production systems of the Plouse (Legett, 1960; Koenig, 2005; Mhler, 2007; Schillnger et l., 2008). Crop yield hs been strongly correlted with wter vilbility (Schillinger et l., 2008). Sptil vribility in soil properties hve been correlted with sptil ptterns observed in soil wter content (Buscc nd Montgomery, 1992; Ibrhim nd Huggins, 2011). Avilble soil wter content in spring ws found to vry from 6.1- to 40.6-cm in the surfce 1.5 m cross 12 h reserch frm field ner Pullmn, WA but vilble wter ws not correlted with whet yield (Pn et l., 2007) s reported by Leggett (1960) nd Schillinger et l. (2008). This lck of 50

70 reltionship between vilble wter nd grin yield chllenges previously held wter-yield reltionships tht re used to predict winter whet N needs. Understnding field-scle vribility in vilbility of soil wter will be criticl to interpreting nd understnding the role of site-specific mngement to improve NUE (Fiez et l., 1995; Pn et l., 2007; Ibrhim nd Huggins, 2011). Drylnd crop productivity in the Plouse region hs been shown to vry both temporlly nd sptilly (Cih, 1984; Mull et l., 1992; Fiez et l., 1994b) due to considerble vribility microclimtic conditions nd soil properties (Mull et l., 1992; Pn et l., 2007). This vribility hs been shown to influence the timing nd mount of vilble wter (Ibrhim et l., 2011), vilble N nd vilble N uptke (Sowers et l., 1994; Huggins nd Pn, 2003) nd overll NUE (Sowers et l., 1994; Fiez et l., 1995; Huggins et l., 2010b). Nitrogen use efficiency hs been reported to rnge from 4 to 34 kg kg -1 within fields nd cross yers in the Plouse region (Sowers et l., 1994; Fiez et l., 1995; Huggins et l., 2010). Despite the considerble vribility, the region continues to be typified by uniform N rtes tht likely contribute to inefficient use of N supplies, other inputs (e.g., seed nd herbicides), nd potentilly vilble soil wter supplies. An dditionl concern in drylnd environments like the Plouse, is tht incresed vegettive biomss stimulted by the ddition of N fertilizers cn lso contribute to greter depletion of vilble wter for post-nthesis grin filling (Entz nd Fowler, 1989). Nitrogen nd seeding rte mngement impcts on crop wter use hve been reported (Pwson et l., 1961; Entz nd Fowler, 1989; Vn Herwrden et l., 1998). Seeding rte impcts on wter use efficiency were observed by Entz nd Fowler (1989) s well s positive correltion between 51

71 wter use efficiency nd spikes m -2, kernel weight, nd biomss t nthesis. Thompkins et l. (1991) reported significnt seed rte effect on growing seson wter use. They reported 4% greter wter use under higher seeding rtes nd greter vilble soil wter in the low seed rte tretments t nthesis. Brown (1971) observed tht incresing mounts of N fertilizer incresed the depth of wter depletion nd cumultive wter use for winter whet. Adjusting winter whet seeding rtes to better mtch vribility in N supply with plnt vilble wter my be importnt for optimizing grin yield nd improving NUE in drylnd griculturl systems of the Plouse. Nitrogen use efficiency hs been shown to vry by crop nd mong vrieties indicting plnt genetic influence on NUE (Dobermn, 2007; Mlcolm nd Hwkford, 2012). Plnt genetic fctors relted to NUE include trits influencing the efficiency in which vilble N supplies re tken up nd utilized by the crop to produce biomss nd grin (Dwson et l., 2008; Mlcolm nd Hwkford, 2012). Genetic x environment x mngement interctions on crop growth nd development s well s NUE underscore the importnce of evlutions tht incorporte soil nd plnt bsed components of NUE (Dobermn, 2007; Huggins et l., 2010). In the Plouse region, the complex topogrphy nd considerble sptil vribility in soil properties results in lndscpe position cting s n environmentl control (Buscc nd Montgomery; Mull, 1992). Improvements to griculturl NUE in Plouse lndscpes will require understnding lndscpe specific drivers tht influence both soil nd plnt physiologicl processes tht regulte NUEwter reltionships. 52

72 Though wter-n interctions hve been long recognized in the Plouse region (Horner nd Vndecyeve, 1950), lndscpe-specific reltionship between crop yield, N supply, nd vilble wter on efficient use of N fertilizer inputs remins mbiguous (Pn et l., 2007). Understnding the impct of N fertilizer ppliction nd seeding rte on the growth nd development of cerel crops, crop wter use nd NUE is lcking in generl but specificlly for the Plouse region. The objectives of this reserch were to evlute the impct of N nd seed rte tretments on N use efficiency nd vilble soil wter depletion in the surfce nd subsurfce for three different lndscpe positions. The specific hypotheses were: (i) NUE cn be improved with lower N rtes nd seed rtes in drier lndscpe positions or yers s compred to wetter lndscpe or yers; nd (ii) incresing NR nd SR results in greter vegettive biomss nd depletion of soil wter for post-nthesis grin filling. METHODS Field plot trils from the 2010, 2011 nd 2012 winter whet hrvest yers were used to evlute lndscpe specific N fertilizer nd seeding rte effects on NUE, boveground biomss t nthesis nd vilble soil wter content t nthesis (Appendix 1). A rndomized complete block, split plot design with N fertilizer rte (NR) s the min plot nd seeding rte (SR) s the subplot were employed cross different lndscpe positions t the Cook Agronomy Frm (CAF), ner Pullmn, WA in ech yer (Appendix 2). For 2010, only the N rte experiment with uniform plnting density (i.e., study 3) ws used. The seeding rte tretments were designed to mnipulte the production nd survivl of winter whet tillers nd provide rnge in the number of spikes per unit re mong different lndscpe positions. 53

73 2010 Nitrogen Rte Experiment with Uniform Plnt Density Soft white winter whet ( OR102 ) ws plnted in pired rows on 30 cm (12 in) centers using no-till drill (Horsh-Anderson) equipped with hoe type openers. An N rte plot scle experiment in the north, summit, nd south slope lndscpe positions ws initited in the spring of 2010 within lrger field-scle N rte study. The field ws seeded t uniform rte of 240 seeds m -2 nd N fertilizer ws pplied t 0, 48, 76, nd 104 kg N h -1 using ure mmonium nitrte (32-0-0) in October of There were four replictes for north nd south slopes nd two replictes for the summit position. Replictes for the summit position were limited by the smll size of the summit lndscpe position for this prticulr field t CAF. The previous crop ws hrd red spring whet ( Hnk ) nd 2012 N Rte x Seed Rte Studies Field plots were seeded nd fertilized on 19 cm (7.5 in) row spcing using Fbro notill double disk plot drill with totl min plot size of 35 m 2 nd subplot size of 8.75 m 2. Nitrogen fertilizer (dry ure, ) ws estblished s the min plot nd bnd pplied below the seed t plnting t rtes of 0, 40, 80, 120, nd 160 kg N h -1. Plnt popultion nd spike density differences were estblished within ech NR strip by seeding t 80, 165, 250, nd 335 seeds m -2. Soft white winter club whet ( Chukr ) ws plnted on October 13 in both 2011 nd Seed weight nd kernels per pound were determined ech yer to clculte the mount of seed weight required to chieve the desired seeding rtes. The previous crop ws grbnzo bens (Cicer rietinum, Sierr ). Components of N Use Efficiency 54

74 Nitrogen nd seed rte impcts on N use efficiency were evluted by prtitioning differences in yield nd grin N into mjor soil nd plnt components of N efficiency. Nitrogen use efficiency nd components were determined from grin yield, grin N, boveground plnt N, pplied N, nd pre- nd post-hrvest root zone soil inorgnic N (150-cm). For this reserch, the NUE ws clculted s the hrvested grin yield (Gw) divided by N supply (Ns) where the N supply includes soil nd fertilizer derived N sources (Huggins nd Pn, 2003). Nitrogen use efficiency nd components terminology re summrized in Tble 3.1. Following Huggins et l. (2010), NUE ws prtitioned into the following components: N retention efficiency (Nv/Ns), vilble N uptke efficiency (Nt/Nv), nd N utiliztion efficiency (Gw/Nt). The N uptke efficiency (Nt/Ns) nd vilble N use efficiency (Gw/Nv) cn be determined from these components. The N uptke efficiency is the boveground N divided by the N supply nd the N utiliztion efficiency is the grin yield divided by the boveground plnt N. Aboveground Biomss nd Avilble Soil Wter t Anthesis Totl boveground biomss (kg h -1 ) t nthesis ws determined from 0.5 m -2 re within ech plot tht ws hrvested when pproximtely 50% of nthers could be observed (i.e., nthesis). Aboveground biomss ws dried t 50 C for two dys nd weighed. Soil profile vilble wter t nthesis for the surfce (0 to 90 cm) nd subsurfce (90 to 150 cm) were determined by summing the vilble soil wter over the pproprite depth increments tht were smpled by 30-cm increments shortly fter nthesis plnt smpling (i.e., 0-30, 30-60, 60-90, nd cm depth increments) (Appendix 1). The vilble soil wter t nthesis ws determined ssuming 110 g kg -1 grvimetric wter concentrtion t the permnent 55

75 wilting point (Fiez et l., 1994b) nd soil bulk density estimtes from nerby geo-referenced monitoring loctions (Huggins, personl communiction). Sttistics An nlysis of vrince ws conducted using the PROC MIXED procedure of SAS (SAS 9.4, SAS Inst., 2012). Tretment mens were considered significntly different t p<0.10. Tukey s method ws used to control the experiment wise error rte for multiple men comprisons. The impct of mngement prctices were evluted by lndscpe for ech site yer due differences in how tretments were imposed (i.e., tretment levels nd rtes) nd differences in the lndscpe positions represented in ech site yer. Person correltion coefficients were generted using the PROC CORR procedure of SAS to investigte the reltionship between vribles (i.e., vilble soil wter t nthesis, nthesis biomss, NUE nd NUE components) (SAS 9.4, SAS Inst., 2012). The strength of reltionship ws defined by the following rnges in the correltion coefficient (r vlue): 0.00 to 0.19, very wek; 0.20 to 0.39, wek; 0.40 to 0.59, moderte; 0.60 to 0.79, strong; nd 0.80 to 1.00, very strong (Evns, 1996). RESULTS Wether The 2012 site yer ws reltively norml precipittion yer while the 2010 site yer ws drier nd the 2011 site yer wetter thn norml (Appendix 3). The 30-yer norml nnul precipittion for the re is 53 cm ( , Pullmn 2NW Wether Sttion, Plouse Conservtion Field Sttion). Cumultive nnul precipittion (Oct 1 to Sept. 30) during the study period ws 47-, 61-, nd 58-cm for 2010, 2011, nd 2012, respectively. The timing nd mount 56

76 of precipittion s well s wrmer winter nd spring tempertures ppered to hve fvored higher yield overll in the 2011 crop yer compred to the 2010 nd 2012 crop yers (Appendix 3). For this study, the summit nd south bckslope positions represented drier lndscpe positions s compred to footslope nd north bckslope positions (Fig. 2.2). Anthesis Biomss nd Remining Avilble Soil Wter Content In 2011, boveground biomss t nthesis incresed significntly with incresing NR nd SR rte though the response to seed rte ws not s gret s the response to NR (Tble 3.1; Fig. 3.3 nd 3.3d). Overll, the south bckslope exhibited higher biomss nd lower vilble soil wter content t nthesis compred to the north nd footslope positions. The footslope exhibited the highest vilble wter compred to the other lndscpe positions. Biomss t nthesis incresed significntly by 34%, 31%, nd 32% s NR incresed from 0 to 160 kg h -1 for the north, foot, nd south bckslope positions, respectively (Fig 3.2). In the north bckslope, nthesis biomss ws significntly higher in the 165, 250 nd 335 seeds m -2 tretment compred to the 80 seeds m -2 tretment (Fig. 3.2d). There ws no significnt effect of SR on nthesis biomss in the footslope nd nthesis biomss ws significntly higher for the 250 nd 335 s compred to the 80 seeds m -2 tretment in the south bckslope. Anthesis biomss decresed slightly, but not significntly, s seed rte incresed from 250 to 335 seeds m -2 in the north bckslope nd footslope, respectively. Avilble wter remining in the surfce 90-cm declined significntly, from 4.34 to nd from 3.66 to 1.20-cm, s N rte incresed from 0 to 160 kg h -1 in the north nd south bckslope, respectively (Fig. 3.2b). In the south bckslope, significnt declines in subsurfce vilble wter were observed t the 120 nd 160 kg N h -1 57

77 rtes. There were miniml to no effects of incresing SR on vilble wter for the 0- to 90 nd 90- to 150-cm depths for ll lndscpe positions (Fig. 3.2e nd 3.2f). In 2012, the footslope hd the highest nthesis biomss nd vilble surfce soil wter content cross NR nd SR tretments (Tble 3.1; Fig. 3.3). There were significnt increses in boveground biomss t nthesis s NR incresed for the north nd south bckslope but not for the footslope position in 2012 (Fig. 3.3). In the south bckslope, nthesis biomss incresed from 5943 to 9220 kg biomss h -1 with n increse in NR from 0 to 80 kg N h -1 nd then declined to 9095 nd 8373 kg h -1 t 120 nd 160 kg N h -1, respectively. Aboveground biomss incresed with n increse in SR rte but significnt effects were miniml fter 165 seeds m -2 (Fig. 3.3d). In the south bckslope biomss declined slightly t the higher SR tretment, continued to increse for the footslope nd reched plteu in the north bckslope though the response ws not significnt (Fig. 3.3d). Avilble soil wter content in the surfce 90-cm decresed significntly from 5.8 to 1.9- nd 6.7 to 3.3-cm s N rte incresed from 0 to 160 kg N h -1 in the north nd south bckslope (Fig. 3.3b). Surfce vilble soil wter content did not decline significntly with n increse in NR or SR for the footslope position (Fig 3.3b nd 3.3e). There ws miniml to no significnt effect of NR on vilble wter in the 90- to 150-cm portion of the soil profile (Fig. 3.3c). There ws no significnt effect of incresing SR on vilble wter in the surfce 0 to 90-cm or subsurfce 90 to 150-cm (Fig. 3.3e nd 3.3f). Nitrogen nd Seeding Rte Effects on NUE 58

78 The impct of mngement prctices were evluted by lndscpe for ech site yer due to the significnce of lndscpe nd site yer differences in significnt NR or SR by lndscpe interctions (Tble 3.2) Hrvest Yer Nitrogen use efficiency (Gw/Ns) decresed from 24.6 to 15.6 kg kg -1 nd from 26.4 to 16.3 kg kg -1 s N rte incresed from 0 to 103 kg N h -1 for the north nd south bckslope, respectively (Tble 3.3). Nitrogen use efficiency ws lowest in the summit position s compred to other lndscpes nd there were no significnt NR effects on NUE or components for this lndscpe (Tble 3.3). In the north bckslope, decreses in NUE were primrily due to the significnt negtive reltionship of N uptke efficiency (Nt/Ns) with NR, where Nt/Ns decresed significntly from 0.51 to 0.39 kg kg -1 s N rte incresed from 0 to 103 kg N h -1. In contrst, decresing NUE with greter pplied N in the south bckslope position ws primrily due to declining N utiliztion efficiency (Gw/Nt), where Gw/Nt decresed significntly from 51 to 35 kg Gw kg Nt -1 s N rte incresed from 0 to 103 kg N h -1 (Tble 3.3) Hrvest yer Nitrogen use efficiency decresed by 14.6, 18.2 nd 18.8 kg kg -1 s N rte incresed from 0 to 160 kg N h -1 for the north, footlslope nd south bckslope, respectively (Tble 3.4; Appendix A-8b). The significnt differences in Gw/Ns, Nt/Ns, nd Nv/Ns mong NR tretments in the footslope ppered to be miniml with differences occurring t the low N rte compred to the higher N rtes (i.e., bove 40 kg h -1 ). Nitrogen utiliztion efficiency declined by 10.4, 9.6, nd 15.4 kg kg -1 with n N rte increse from 0 to 160 kg N h -1 in the north, foot, nd south 59

79 slope, respectively (Tble 3.4). Nitrogen uptke efficiency decresed by 0.18, 0.24 nd 0.15 s NR incresed for the north, footslope nd south bckslope, respectively. A significnt NR effect on vilble N uptke efficiency (Nt/Nv) ws only observed in the south bckslope in 2011 but the effects ppered to be miniml (Tble 3.1). Nitrogen retention efficiency (Nv/Ns) declined by s much s 0.22, 0.30, nd 0.20 kg kg -1 s NR incresed in the north, foot, nd south slopes, respectively (Tble 3.4). In the north bckslope, Gw/Ns incresed by 11 kg kg -1 s SR incresed from 80 to 335 seeds m -2 (Tble 3.4). In the south bckslope, Gw/Ns ws 16% nd 7% greter for the 165 nd 250 seeds m -2 s compred to the 335 seeds m -2 tretment. There were no significnt SR effects on Gw/Nt or Nt/Nv for ll three lndscpe positions. A significnt increse in Nv/Ns, by 0.19 kg kg -1, occurred s SR incresed from 80 to 335 seeds m -2 ws observed in the north bckslope. There ws slight but significnt SR effect on Nv/Ns in the footslope with Nv/Ns rnging from 0.65 to 0.77 kg kg -1 cross SR tretments nd significnt differences limited to the 80 nd 250 seeds m -2 tretments (Tble 3.4). In the south bckslope, Nv/Ns incresed from 0.84 to 0.92 kg kg -1 s SR incresed from 80 to 165 seeds m -2 but then declined to 0.88 nd 0.76 kg kg -1 t the 250 nd 335 seeds m -2 tretments, respectively Hrvest Yer Nitrogen use efficiency decresed by 15, 22, nd 14 kg kg -1 s N rte incresed from 0 to 160 kg N h -1 for the north, foot, nd south slope positions, respectively (Tble 3.5; Appendix A- 8b). Slight but significnt decreses in Gw/Nt s N rte incresed were observed in the north (by 6 kg kg -1 ) nd south bckslope (by 8 kg kg -1 ). In the south bckslope significnt differences in 60

80 Gw/Nt were limited to differences between the 0 nd 160 kg N h -1 N rtes with Gw/Nt of 53 nd 45 kg kg -1, respectively. Nitrogen uptke efficiency decresed by s much s 0.30, 0.34 nd 0.19 kg kg -1 with increses in N rte for the north, foot nd south bckslope, respectively. The north bckslope ws the only lndscpe position to exhibit significnt NR effect on Nt/Nv. Nitrogen retention efficiency decresed significntly from 0.98 to 0.75, 1.0 to 0.57, nd 0.86 to 0.54 kg kg -1 s N rte incresed from 0 to 160 kg h -1 in the north, foot, nd south slopes, respectively. There ws significnt NR*SR interction on Nt/Nv in 2012 (Tble 3.5) nd from the interction plot, it ws observed tht Nt/Nv initilly increses with NR but then declines s NR continues to increse for the 80, 165 nd 250 seeds m -2 tretment levels. However, in the 335 seeds m -2 tretment Nt/Nv ws highest t 0 kg N h -1 nd did not exhibit the sme decline s NR incresed (Fig. 3.1). Nitrogen use efficiency significntly incresed, by s much s 4.4 nd 7.9 kg kg -1, s SR incresed for the north nd footslope positions, respectively (Tble 3.5). Nitrogen use efficiency incresed, but not significntly, from 20.6 to 26.5 kg kg -1 s SR incresed from 80 to 335 seeds m -2 in the south bckslope. A slight but significnt increse in Gw/Nt with incresing SR ws observed in the north bckslope. Seed rte did not hve significnt effect on Gw/Nt for the foot or south slope. There ws no significnt SR effect on Nt/Ns for the north or south bckslope positions nd miniml effect in the footlslope with the highest Nt/Ns t the 250 seeds m -2 (0.63 kg kg -1 ) followed by the 335 (0.58 kg kg -1 ), 80 (0.55 kg kg -1 ) nd 165 (0.51 kg kg -1 ) seeds m -2 tretment. Avilble N uptke efficiency incresed significntly from 0.70 to 0.81 kg kg -1 s SR incresed from 80 to 335 seeds m -2 for the south bckslope. There ws little 61

81 (footslope) to no significnt effect (north nd south bckslope) of incresing SR on Nv/Ns in 2012 s ws observed in In the footslope, Nv/Ns rnged from 0.62 to 0.78 kg kg -1 with the lowest in the 165 seeds m -2 tretment nd highest Nv/Ns in the 250 seeds m -2 tretment. Person Correltion for Surfce Avilble Soil Wter Content nd Select Vribles In the reltively wet conditions of 2011 (Appendix 3), the positive ssocition between surfce vilble wter nd subsurfce vilble wter t nthesis ws wek in the north bckslope (r=0.246), moderte in the footslope (r=0.425) nd moderte in the south bckslope (r=0.496) (Tble 3.6). The negtive correltion between biomss nd surfce vilble wter t nthesis ws modertely strong in the north nd south bckslope (r= nd , respectively) nd insignificnt in the footslope (p=0.535). Surfce vilble soil wter content ws wekly but significntly ssocited with Gw/Ns in the south bckslope (r=0.395, p=0.0003). The significnt positive ssocition between surfce vilble wter nd Gw/Nt ws wek in the north bckslope (r=0.284) nd moderte in the south bckslope (r=0.580). Significnt negtive correltions with Nt/Nv nd positive correltions with Nv/Ns occurred in the footslope nd south bckslope but were wek. Positive correltion between surfce nd subsurfce vilble wter content t nthesis observed in the north nd south bckslope were moderte nd wek, respectively. Surfce vilble wter ws moderte to strongly ssocited nd negtively correlted with nthesis biomss for ll three lndscpes. Modertely strong nd positive correltion mong surfce vilble wter nd Gw/Ns were observed in the north bckslope (r=0.513). The correltion with Gw/Nt nd Nt/Ns ws moderte for the north bckslope (r=0.402 nd 0.458, respectively) 62

82 nd wek for the footslope (r= nd , respectively) with no significnt correltion in the south bckslope. Avilble N uptke efficiency ws negtively nd wekly correlted to surfce vilble wter content t nthesis in the footslope (r=-0.333) nd south bckslope (r= ). N retention efficiency ws significntly correlted with surfce vilble wter t nthesis for ll three lndscpe positions. The ssocition between surfce vilble wter nd Nv/Ns ws positive for the north nd south bckslope but negtive for the footslope. DISCUSSION Improving NUE: The Role of N Rte Koenig (2005) presented trget NUE vlues required to chieve N fertiliztion gols for whet. The NUE trget for soft white winter whet is Gw/Ns of 22.2, bsed on unit N requirement (UNR) of (0.045 kg kg -1 or 1/NUE) nd, in turn, ssumes n Nt/Ns of 0.5 (50% N uptke efficiency) nd therefore N utiliztion efficiency (Gw/Nt) of 44.4 kg kg -1. These trget NUE nd N component efficiencies in conjunction with the nlysis of vrince results provide mens to evlute the hypotheses tht drier lndscpe positions or yers should be N fertilized nd seeded t lower rte thn wetter lndscpe positions or yers. The rnge in NUE observed in this study exceed the rnges tht hve been previously reported cross Plouse lndscpes. Nitrogen use efficiency in the dry yer of 2010 were more similr to the kg kg -1 reported by Fiez et l. (1995), 18 to 24 kg kg -1 reported by Sowers et l. (1994) nd 4 to 34 kg kg -1 rnge reported by Huggins et l. (2010). Wetter conditions due to wether or lndscpe specific vilble soil wter content resulted in higher NUE thn previously reported by incresing both Gw/Nt nd Nt/Ns. 63

83 Nitrogen utiliztion efficiency decresed with incresing N rte s seen by Huggins et l. (2010) nd Huggins nd Pn (1993) but were highest nd bove trget levels in 2011, prticulrly in the footslope nd south fcing bcklsope. Nitrogen utiliztion efficiencies were lowest nd below trget vlue of 44.4 kg kg -1 for ll lndscpe positons in the dry conditions of 2010 nd especilly in the driest lndscpe position (i.e., summit). Huggins et l. (2010) reported nitrogen utiliztion efficiency (Gw/Nt) to rnge from 28.9 to 45.3 for hrd red spring whet. Fiez et l., (1995) found Gw/Nt t optimum soft white winter whet yield to rnge from 37.3 to 46.5 over two different site yers. The Gw/Nt rnged from 31.7 in the 2010 summit to 62.2 in the 2011 south bckslope. This rnge is greter thn tht reported by Huggins et l., (2010) nd Fiez et l. (1995) nd is ttributed to the rnge in wether nd residul soil inorgnic N conditions cross site yers. The rnge in Nt/Ns mong lndscpe positions nd NR tretments were generlly similr to the 0.40 to 0.70 rnge reported by Huggins et l., (2010) for hrd red spring whet. Overll yers nd NR tretments, the Nt/Ns rnged from 0.39 to 0.87, 0.46 to 0.80, 0.42 to 0.80, nd 0.39 to 0.52 kg kg -1 for the north bckslope, footlslope, south bckslope nd summit, respectively. These rnges re higher thn those observed in the N rte tril dt of Fiez et l. (1995) on footslope (0.45 to 0.46), north bckslope (0.38 to 0.59), shoulder (0.44 to 0.55) nd south bckslope (0.54 to 0.67) positions. In the current reserch, lower rnges nd vlues of Nt/Ns were often ssocited with norml to dry yers, drier lndscpe positions nd the highest NR tretment. The highest overll Nt/Ns were chieved in the wet wether conditions of 2011 s well s the wetter lndscpe positions in the more norml wether conditions of

84 Avilble N uptke efficiency (Nt/Nv) ws found to be reltively stble cross site yers with little response to NR cross lndscpes with vlues similr to nd often greter thn the 78% reported by Sowers et l. (1994) for soft white winter whet. The high Nt/Nv observed throughout this study indicted tht the winter whet ws reltively efficient t tking up sources of vilble N nd tht vritions in Nv/Ns mong lndscpes hd greter impct on Nt/Ns. Inefficiencies in N uptke efficiency (Nt/Ns) hve been ttributed to N loss in Plouse lndscpes (Moll et l., 1982; Fiez et l., 1995; Huggins nd Pn, 2003). Nitrogen retention efficiency (Nv/Ns) is n NUE component used to evlute how much of the N supply ws vilble to the plnt nd to ssess N loss. Low N retention efficiency indictes N loss, while high N retention efficiency coupled with low Nt/Nv cn indicte poor mtch between vilble N nd crop N demnd (Huggins nd Pn, 2003; Huggins et l., 2010). The reltively lrge contribution of declining Nv/Ns to lower Nt/Ns vlues nd reltively high Nt/Nv observed cross lndscpes nd tretments in this study supports tht N vilbility is limiting N uptke efficiency under dry wether s well s wet nd dry lndscpe positions s previously reported (Fiez et l., 1995). The Nv/Ns rnged from 0.47 to 0.98, 0.57 to 1.0, 0.54 to 0.95, nd 0.46 to 64 for the north bckslope, footslope, south bckslope, nd summit, respectively, s N rte incresed over ll yers. These rnges re greter thn tht reported by Huggins et l. (2010) for plot reserch (0.70 to 0.98) nd smller thn the rnge reported for field reserch (0.20 to over 1.00). It ws hypothesized tht improvements to NUE cn be chieved with lower NR nd SR in drier lndscpe positions or yers s compred to wetter lndscpe positions or yers nd tht 65

85 incresing NR nd SR results in greter vegettive biomss nd depletion of soil wter for postnthesis grin filling. This study showed tht NUE trgets could be chieved with lower NR for ll lndscpe positions in dry yers but especilly in drier lndscpes under dry wether conditions. Trget NUE s were chieved with lower NR in drier lndscpe positions (i.e, south bcklope) under norml wether conditions. In wetter conditions (i.e., 2011) trget NUE ws chieved t the sme high N rte (160 kg N h -1 ) for ll lndscpe positions. Yet under norml conditions (i.e., 2012), N rte reductions in wet lndscpes (i.e., footslope) improved NUE by reducing N loss. In contrst to the conclusions of Fiez et l. (1994) tht lndscpe lone ws not useful for delineting zones of productivity, this reserch showed tht lndscpe does provide useful criterion for delineting spects of crop performnce relted to NUE. In the Plouse region, the complex topogrphy nd considerble sptil vribility in soil properties results in lndscpe position cting s n environmentl control (Buscc nd Montgomery; Mull, 1992). For this reson, NUE evlutions of site-specific mngement will require understnding lndscpe specific drivers tht influence both soil nd plnt physiologicl processes cross the rnge in wether conditions. North Bckslopes The dry yer (2010) ws the only yer where the north bckslope did not chieve the trget NUE cross NR tretments. The 0.50 Nt/Ns trget ws only chieved t the 0 kg N h -1 rte s compred to 2011 nd 2012 where it ws chieved t ll NR in the north bckslope. High residul soil N following the low yielding HRSW crop tht preceded the 2010 winter whet crop likely contributed to the lck of NR response nd highlights the importnce of pre-plnt 66

86 soil smpling for inorgnic N. The low Nv/Ns but high Nt/Nv in the 2010 north bckslope indictes tht N loss to competing pthwys (e.g. immobiliztion) in dry conditions reduced N vilbility. Nitrogen utiliztion efficiency trgets were chieved t lower N rtes in drier yers (75 kg N h -1 in 2010 nd 120 kg N h -1 in 2012) s compred to wetter wether conditions (160 kg N h -1 in 2011) indicting tht yield ws limited by wter-stress tht induced low N uptke efficiency in dry to norml conditions. Furthermore, under norml conditions, wter stress ppered to be excerbted by incresing the N ppliction rte. South Bckslopes Nitrogen fertilizer rtes of 48, 160, nd 40 to 80 kg N h -1 resulted in chieving the minimum trgets for NUE nd components in 2010, 2011, nd 2012 respectively. The low NUE in 2010 ws due mostly to NR impcts on Gw/Nt, though Nt/Ns hd dropped slightly below the 0.50 kg kg -1 trget. The south bckslope ws the driest lndscpe in 2011 nd Nitrogen utiliztion efficiency declined with incresing NR in the wet nd norml conditions of 2011 nd 2012 but not below the 44.4 kg kg -1 trget. Under norml conditions (2012), Nt/Ns trgets were not chieved t N rtes of 40 kg h -1 nd bove leding to NUE s below the 22.2 trget in most NR tretments. The declining Nv/Ns with high Nt/Nv indicted tht N loss reduced N vilbility under norml conditions s opposed to Gw/Nt under dry conditions (2010). Furthermore, incresing NR ws ssocited with incresed biomss t nthesis nd subsequently greter depletion of surfce vilble wter in both 2011 nd This indictes tht high N rtes under norml to dry conditions in drier lndscpe positions hve the potentil 67

87 to induce or excerbte moisture stress relted N deficiencies (2012) nd yield limittions (2011). Footslopes There ws similr rnge in NUE for the 2011 nd 2012 footslope positions nd the footslope hd the highest vilble wter compred to the other lndscpes. Nitrogen use efficiency declined with incresing NR nd the minimum trget NUE ws reched t fertilizer rtes of 160 nd 120 kg N h -1 in the wet (2011) nd norml (2012) wether yers, respectively. In both yers, NUE declines were the result of Nt/Ns below the 50% trget. Incresing NR resulted in incresed biomss but depletion of soil vilble wter resources for post-nthesis grin filling ws not observed. The Nt/Ns slightly below 50% in the norml conditions of 2012 were ssocited with lower Nv/Ns, nd coupled with higher surfce vilble soil wter t nthesis, indicte tht N loss such s leching or denitrifiction re reducing N vilbility in the footslope t the higher N rtes. Summit There ws no NUE or NUE component response to NR indicting no N should hve been dded to this lndscpe position. The NUE vlues in this lndscpe were considerbly lower thn the other lndscpes in 2010 nd compred to the other lndscpes nd yers of this reserch. Nitrogen uptke nd utiliztion efficiencies were poor in 2010 nd Gw/Nt ws well below the trget of 44.4 kg kg -1 cross ll N rtes. A lck of response to NR ws likely result of high residul soil inorgnic N coupled with wter stress given the low precipittion nd vilble soil wter content in 2010 (Tble 2.1). Nitrogen uptke efficiency decresed from

88 to 0.39 kg kg -1 s N rte incresed nd the response ppered to be relted to loss of the N supply to immobiliztion nd possibly strnding of N in upper portions of the soil profile. Improving NUE: The Role of Seed Rte The effect of winter whet seeding rte on NUE hs not been extensively studied nd t present remins poorly understood (Di et l., 2013). Vrition in winter cerel crop development cross lndscpe positions of the Plouse hve been ssocited with vribility in soil processes such s erosion, mount of plnt vilble wter, presence of root restrictive lyers nd vilbility of nutrient supplies (Pn nd Hopkins, 1991). Altering seeding rtes to control vegettive growth nd more efficiently utilize N nd vilble wter supplies offers prcticl mngement strtegy to ensure sufficient wter vilble for post-nthesis grin filling nd void hying-off (vn Herwrden et l., 1998). It ws hypothesized tht incresing SR would result in greter vegettive biomss nd depletion of soil wter for post-nthesis grin filling nd tht improvements to NUE could be chieved with lower SR in drier lndscpe positions or yers s compred to wetter lndscpe positions or yers. Trget NUE nd optimum nthesis biomss could be chieved or exceeded with lower SR (i.e., 165 seed m -2 ) thn typiclly used t CAF (250 seeds m -2 ) indicting tht t lest 34% reduction in typicl seeding rtes is fesible. It ws observed tht lower SR (80 seeds m -2 ) chieved trget NUE s of 22.2 kg kg -1 in wet versus dry conditions, which ws contrry to the originl hypotheses. In this reserch, incresing seeding rte did not result in significnt increses in nthesis biomss or depletion of vilble soil wter in the surfce or subsurfce s hypothesized. Tompkins et l. (1991) found tht higher seeding rtes used significntly more 69

89 wter over the growing seson s compred to lower seeding rtes. Nitrogen rte nd not SR resulted in greter vegettive biomss tht ws ssocited with depletion of nthesis vilble soil wter content. In ddition, incresing the SR resulted in improvements to NUE in both 2011 nd Di et l. (2103) concluded tht NUE could be improved through optimizing seed rte due to increses in Nt/Ns but overll the NUEs in tht study were much lower (rnged from 17 to 20 kg kg -1 ) thn generlly observed in the SR portion of this study (rnge of 27 to 41 kg kg -1 ). Furthermore, the two yer experiments of Di et l. (2013) were conducted under irrigtion nd in single lndscpe position. The Gw/Nt in Di et l. (2013) rnged from 55 to 87 kg kg -1 nd in this study rnged cross seeding rtes nd yers from 44.0 to 50.5, 50.4 to 58, nd 45 to 54 kg kg -1 for the north bckslope, footslope, nd south bckslope, respectively. The rnge in Nt/Ns cross SR tretments for this reserch (0.46 to 0.75 kg kg -1 ) were somewht similr to the rnge observed by Di et l. (2013). Lndscpe specific response ppered to be importnt to understnding the role of soil versus crop physiologicl response in NUE with increses in seed rte under wet (2011) versus dry (2012) conditions. North Bckslope Trget NUE ws met or exceeded in the north bckslope cross ll seed rtes in both yers. A SR of 80 seeds m -2 would hve resulted in chieving the minimum NUE trgets in wet nd norml conditions. This indicted tht improvements to NUE in wetter lndscpes, nd lso in wetter thn norml yers, occur s SR increse but re not necessry to chieve the minimum NUE of 22.2 kg kg -1. There ws no biomss response to incresing seed rte from

90 to 335 seed m -2 nd lso n overll lck of SR impct on vilble wter t nthesis. Under wet wether conditions (2011), increses in NUE with SR were driven by incresing Nt/Ns but under norml wether conditions by increses in Gw/Nt s SR incresed. It ppered tht under wet conditions, lrge frction of the N supply my be vilble from the N cycle process of minerliztion thereby contributing to greter N uptke efficiencies s compred to the norml wether conditions in Overll, these results indicte tht in north bckslopes, 68% reduction in SR would llow NUE gols to be met under norml nd wetter thn norml wether conditions. South Bckslope Though reltively dry lndscpe position, greter NUE s were observed under wet wether conditions compred to norml conditions in the south bckslope. Nitrogen use efficiency trgets were obtined cross ll SR in 2011 nd t minimum SR of 165 seeds m -2 for the south bckslope in Therefore, 34% nd 68% reductions in typicl SR t CAF will result in meeting NUE trgets in wetter nd drier conditions, respectively. This ws ttributed to strong bility of the winter whet used in this reserch to compenste for low seeding rte under wet conditions given the wrmer tempertures of south fcing spects. In 2012, the Nt/Ns ws lower thn the 50% trgets for the 80, 165, nd 335 seeds m -2 tretments suggesting sink size limittion of N uptke under norml conditions in dry lndscpes. By comprison, the reltively drier south bckslope positions under wet conditions hd n Nt/Ns rnge of 0.63 to 0.75 kg kg -1 cross SR tretments. There is evidence tht N loss to competing pthwy reduced NUE for the south bckslope under norml conditions. Contrry to the hypotheses, 71

91 higher rther thn lower SR improved NUE under norml conditions in dry south bckslope positions. Footslope The foot slope position hd greter nthesis vilble wter content in the surfce compred to the north nd south bckslope. The NUE trget of 22.5 kg kg -1 ws chieved or exceeded cross ll SR in the footslope for both 2011 nd Similr rnges in Nv/Ns were observed in both wet (0.49 to 0.58) nd norml (0.51 to 0.63) wether conditions in this wetter lndscpe position. There ws lso similr rnge in Gw/Nt cross wet (54 to 58 kg kg -1 ) nd norml (50 to 56 kg kg -1 ) conditions with slightly higher Gw/Nt under wet conditions. Overll, these results indicte tht in wetter lndscpes 68% reduction in SR would llow the NUE trget of 22.2 kg kg -1 to be met under norml nd wetter thn norml wether conditions. Implictions Lndscpe nd NR present the lrgest influence on vegettive biomss nd vilbility nd depletion of wter reserves going into the grin filling period. In ddition to wether nd lndscpe, this reserch showed thn N rte mngement, more so thn SR mngement, stimultes vegettive biomss nd depletion of vilble soil wter in north nd south bckslopes. This hs prticulrly negtive implictions for chieving or exceeding NUE gols in dry wether or lndscpe positions. This reserch hs shown tht seeding rte increses my improve NUE without significnt impcts on vilble wter throughout the root zone. Improving crop yield nd N mngement under drylnd crop production will continue to require simultneous understnding of soil wter nd N dynmics. Nitrogen use efficiency 72

92 component nlysis provided frmework for dignosing lndscpe specific drivers nd mngement effects on chieving trget NUE. From the NR nd SR tretment effects on NUE lone, there does pper to be role for greter reductions in NR in drier wether conditions nd lndscpes s compred to wetter conditions nd lndscpes. Eqully s importnt, this reserch lso showed tht reducing NR in wet lndscpe positions under norml conditions cn reduce N loss. Reducing SR by pproximtely 34% in dry lndscpes nd 68% in wetter lndscpes or wether conditions ppered to be effective in chieving NUE, pproprite vegettive biomss, nd vilble wter resources mong north bckslope, footslope, nd south bckslope positions. The ptterns in yield response nd extremes in NUE cross Plouse lndscpes indictes tht uniform seeding nd N fertilizer rtes my not be sufficient to simultneously chieve grin yield, protein, nd NUE gols (Huggins nd Pn, 1993; Pn et l., 2007; Huggins et l., 2010). In drylnd cropping systems, where rinfll is limited nd vrible in distribution, it becomes incresingly importnt to void N ppliction rtes tht might result in hying-off (vn Herwrden et l., 1998). Hying-off is thought to be driven by high N supply nd dequte wter tht stimultes crop biomss ccumultion nd sets potentilly high yield tht cnnot be supported by conditions lter in the growing seson (e.g., terminl drought) (vn Herwrden et l., 1998). Nitrogen fertilizer pplictions tht contribute to hying off further contribute to economic loss from not only yield declines but lso for the N fertilizer tht indvertently reduced yield. This study focused on differences in NUE response to N nd seed rte mong wet nd dry lndscpes nd demonstrted tht considerble vrition exists in the 73

93 NR nd SR required to simultneously chieve yield longside trget NUE gols. For this reserch to be pplicble to growers, future reserch should trget site-specific NR nd SR mngement improvements to NUE tht consider optimizing grin yield nd yield qulity. Additionl reserch is lso needed to more clerly elucidte site-specific yield, NUE, nd vilble wter reltionships tht cn be optimized through N nd seed rte mngement. SUMMARY AND CONCLUSIONS In this reserch wether conditions vried considerbly from yer to yer but lndscpe remined significnt fctor effecting vilble wter t nthesis, nthesis biomss, nd NUE. This reserch expnds the lndscpe scle understnding of NUE by highlighting tht differences in NUE mong wet versus drier lndscpe positions is most ssocited with improving Nv/Ns in wet conditions nd overcoming wter-stress induced limittions on Nv/Ns nd Gw/Nt in drier conditions. This study showed tht NUE trgets could be chieved with lower NR for ll lndscpe positions in dry yers but especilly in drier lndscpes in dry yers. Overll, NUE trgets could be chieved with 34 to 68% lower SR thn typiclly used t CAF nd especilly in wet yers or lndscpe positions. Nitrogen rte rther thn SR hd greter impct on vegettive biomss nd depletion of vilble soil wter content t nthesis. Future reserch should include site-specific N nd seed rte mngement tht considers NUE longside grin yield nd yield qulity to ensure tht environmentl performnce is not t the detriment of economic performnce. 74

94 REFRENCES CITED Brown, P.L Wter use nd soil wter depletion by drylnd winter whet s ffected by nitrogen fertiliztion. Agron. J. 63: Cssmn, K.G Ecologicl intensifiction of cerel production systems: yield potentil, soil qulity, nd precision griculture. Proc. Ntl. Acd. Sci. 96: Cssmn, K.G., A. Dobermnn, nd D. T. Wlters Agroecosystems, nitrogen-use efficiency, nd nitrogen mngement. Ambio. 31(2): Cih, A.J Slope position nd grin yield of soft white winter whet. Agron. J. 76: Di, X, X. Zhou, D. Ji, L. Xio, H. Kong, nd M. He Mnging the seeding rte to improve nitrogen-use efficiency of winter whet. Field Crops Res. 154: Dwson, J.C., D.R. Huggins, nd S.S. Jones Chrcterizing nitrogen use efficiency in nturl nd griculturl ecosystems to improve the performnce of cerel crops in lowinput nd orgnic griculturl systems. Field Crops Res. 107: Dobermn, A.R Nitrogen use efficiency Stte of the rt. Agronomy & Horticulture Fculty Publictions. Pper 316. Avilble online t ccessed 2/2/2015. Dobermn, Nutrient use efficiency mesurement nd mngement. In Fertilizer Best Mngement Prctices First Edition. Interntionl Fertilizer Industry Assocition, Pris, Frnce. pgs Entz nd Fowler, Influence of crop nd wter environment nd dry mtter ccumultion on grin yield of no-till winter whet. Cn. J. Plnt Sci. 69: Fiez. T.E., B. C. Miller, nd W.L. Pn Assessment of sptilly vrible nitrogen fertilizer mngement in winter whet. J. Prod. Agric. 7(1): Fiez et l., 1994b. Winter whet yield nd grin protein cross vried lndscpe positions. Agron. J. 86: Fiez et l., Nitrogen use efficiency of winter whet mong lndscpe positions. Soil Sci Soc. Am. J. 59:

95 Hrdy. R.W.F nd U.D. Hvelk Nitrogen fixtion reserch: key to world food? Science 188 (4188): Hrgrove, W.L., A.L. Blck, nd J.V. Mnnering Cropping strtegies for efficient use of wter nd nitrogen: Introduction. In Cropping strtegies for efficient use of wter nd nitrogen. Eds. Hrgrove et l. ASA Specil publiction number 51. p 1-5. Hwkesford, M.J The diversity of nitrogen use efficiency for whet vrieties nd the potentil for crop improvement. Better Crops. 96 (3): Huggins, D.R. nd W.L. Pn Nitrogen Efficiency Component Anlysis: An evlution of cropping system differences in productivity. Agron. J. 85: Huggins, D.R. nd W.L. Pn Key indictors for ssessing nitrogen use efficiency in cerelbsed groecosystems. J. Crop Production 8: Huggins, D Site-specific N mngement for direct-seed cropping systems. Chpter 16 in Kruger, C., G. Yorgey, S. Chen, H. Collins, C. Feise, C. Frer, D. Grntstein, S. Higgins, D. Huggins, C. McConnell, K. Pinter, C. Stöckle Climte Friendly Frming: Improving the Crbon Footprint of Agriculture in the Pcific Northwest. CSANR Reserch Report Wshington Stte University: Friendly-Frming-Finl-Report/. Huggins, D., W. Pn, nd J. Smith Yield, protein nd nitrogen use efficiency of spring whet: evluting field-scle performnce. Chpter 17 in Kruger, C., G. Yorgey, S. Chen, H. Collins, C. Feise, C. Frer, D. Grntstein, S. Higgins, D. Huggins, C. McConnell, K. Pinter, C. Stöckle Climte Friendly Frming: Improving the Crbon Footprint of Agriculture in the Pcific Northwest. CSANR Reserch Report Wshington Stte University: Ibrhim, H.M. nd D.R, Huggins Sptio-temporl ptterns of soil wter storge under drylnd griculture t the wtershed scle. Journl of Hydrology. 404: Keller, C.K., J.L. Smith, nd R.M. Allen-King Nitrte in tile dringe of the semirid Plouse Bsin. J. Environ. Qul. 37: Koenig, R.T Drylnd winter whet. Estern Wshington nutrient mngement guide. EB1987. Wshington Stte University. WSU Extension Publishing nd Printing. 76

96 Mhler, R.L Northern Idho Fertilizer Guide: Winter Whet. CIS453. University of Idho, Moscow, ID. McCool, D.K. nd R.D. Roe Long-term erosion trends on croplnd in the Pcific Northwest. ASAE Section Meeting Pper No. PNW Pcific Northwest Section Meeting, Albert, Cnd September ASAE, St. Joseph, MI. Mull, D.J., A.U. Bhtti, M.W. Hmmond, nd J.A. Benson A comprison of winter whet yield nd qulity under uniform versus sptilly vrible fertilizer mngement. Agric. Ecosys. Environ. 38: Pn, W.L. nd A.G. Hopkins Plnt development, nd N nd P use of winter brley. I. Evidence of wter stress-induced P deficiency in n eroded toposequence. Plnt nd Soil 135:9-19. Pn, W.L., W. Schillinger, D. Huggins, R. Koenig, nd J. Burns Fifty yers of predicting whet nitrogen requirements in the Pcific Northwest U.S.A. Ppendick, R.I Frming Systems nd conservtion needs in the Northwest Whet Region. Am. J. Alt. Agric. 11(2&3): Pwson, W.W., O.L. Brough, J.P. Swnson, nd G. M. Horner Economics of cropping systems nd soil conservtion in the Plouse. Pierce, F.J. nd C.W. Rice, Impct of crop rottion on wter nd N use. In Cropping strtegies for efficient use of wter nd nitrogen. Eds. Hrgrove et l. ASA Specil publiction number 51. p Rsmussen, P.E., S.L. Albrecht, R.W. Smiley Soil C nd N chnges under tillge nd cropping systems in semi-rid Pcific Northwest griculture. Soil Tillge Res. 47: Ro, A.C.S, J.L. Smith, V.K. Jndhyl, R.I. Ppendick, nd J. F. Prr Cultivr nd climtic effects on the protein content of soft white winter whet. Agron. J. 85: Run, W.R. nd G. V. Johnson Improving nitrogen use efficiency for cerel production. Agron. J. 91: Robertson, G.P., P.M. Vitousek Nitrogen in griculture: blncing the cost of n essentil resource. Annu. Rev. Environ, Resour. 34:

97 Schillinger, W.F., S.E. Schofstoll, nd J. R. Alldredge Avilble wter nd whet grin yield reltions in Mediterrnen climte. Field Crops Reserch. 109: Snyder, C.S. nd T.W. Bruulsem Nutrient use efficiency nd effectiveness in North Americ: indices of gronomic nd environmentl benefit. Interntionl Plnt Nutrition Institute (IPNI) publiction Sowers, K.E., B.C. Miller, nd W.L. Pn Optimizing yield nd grin protein in soft white winter whet with split nitrogen pplictions. Agron. J. 86: Tompkins, D.K., G.E. Hultgreen, A.T. Wright, nd D.B. Fowler Seed rte nd row spcing of no-till winter whet. Agron. J. 83: Vn Herwrden, A.F., G.D. Frquhr, J.F. Angus, R.A. Richrds, nd G.N. Howe Hyingoff, the negtive grin yield response of drylnd whet to nitrogen fertilizer I. Biomss, grin yield, nd wter use. Aust. J. Agric. Res. 49:

98 Tble 3.1. Probbilities (Pf>F) for winter whet biomss, surfce vilble wter nd subsurfce vilble wter t nthesis s ffected by lndscpe, N ppliction rte nd seeding rte by site yer t the Cook Agronomy Frm, ner Pullmn, WA. Yer Source df Biomss t Anthesis Avilble wter Surfce Subsurfce 2010 N Rte 3 n.. n.. n.. Lndscpe 2 n.. n.. n.. N Rte*Lndscpe 6 n.. n.. n N Rte 4 < < Seeding Rte 3 < N Rte*Seeding Rte Lndscpe 2 < < < N Rte*Lndscpe Seeding Rte*Lndscpe N Rte*Seeding Rte*Lndscpe N Rte 4 < < Seeding Rte 3 < N Rte*Seeding Rte Lndscpe 2 < < < N Rte*Lndscpe Seeding Rte*Lndscpe N Rte*Seeding Rte*Lndscpe Totl boveground biomss t nthesis. Surfce nd subsurfce vilble wter content is for 0 to 90-cm nd 90 to 150-cm. n.. not pplicble. 79

99 Tble 3.2. Probbilities (Pf>F) for winter whet grin yield nd yield components s ffected by lndscpe, N ppliction rte nd seeding rte by site yer t the Cook Agronomy Frm, ner Pullmn, WA. Yer Source df Gw/Ns Gw/Nt NtNs NtNv Nv/Ns 2010 N Rte 3 < Lndscpe 2 < N Rte*Lndscpe N Rte 4 <.0001 <.0001 < <.0001 Seeding Rte N Rte*Seeding Rte Lndscpe 2 <.0001 <.0001 <.0001 <.0001 <.0001 N Rte*Lndscpe Seeding Rte*Lndscpe 6 < < <.0001 N Rte*Seeding Rte*Lndscpe N Rte 4 <.0001 <.0001 < <.0001 Seeding Rte N Rte*Seeding Rte Lndscpe 2 <.0001 <.0001 <.0001 <.0001 <.0001 N Rte*Lndscpe 8 < < Seeding Rte*Lndscpe N Rte*Seeding Rte*Lndscpe Gw/Ns: N Use Efficiency; Gw/Nt: N utiliztion efficiency; Nt/Ns: N uptke efficiency; Nt/Nv: vilble N uptke efficiency; Nv/Ns: N retention efficiency 80

100 Tble 3.3. Nitrogen rte effect on nitrogen use efficiency nd components for soft white winter whet by lndscpe for Lndscpe nd Tretment Gw/Ns GW/Nt NtNs NtNv Nv/Ns North Bckslope N Rte, kg N h b 45.1 b 0.45 b b bc 38.5 b 0.45 b b c 39.9 b 0.39 b b Pf>F South Bckslope N Rte, kg N h b 45.1 b bc 39.5 bc c 34.9 c Pf>F Summit N Rte, kg N h Pf>F Gw/Ns: N Use Efficiency; Gw/Nt: N utiliztion efficiency; Nt/Ns: N uptke efficiency; Nt/Nv: vilble N uptke efficiency; Nv/Ns: N retention efficiency. Within columns, mens followed by the sme letter re not significntly different t the 10% level. 81

101 Tble 3.4. Nitrogen nd seeding rte effect on nitrogen use efficiency nd components for soft white winter whet by lndscpe for Lndscpe nd Tretment Gw/Ns Gw/Nt NtNs NtNv Nv/Ns North Bckslope N Rte, kg N h b 49.8 b 0.70 b b bc 49.6 b 0.67 bc bc c 48.0 bc 0.61 c c c 44.6 c 0.65 bc bc Seeding Rte, seeds m c c c bc bc bc b b b N Rte <.0001 < <.0001 Seeding Rte < < <.0001 N Rte*Seeding Rte Footslope N Rte, kg N h b b b b 56.8 b 0.49 b b b 52.4 b 0.51 b b b 50.6 b 0.46 b b Seeding Rte, seeds m b b b N Rte < <.0001 Seeding Rte N Rte*Seeding Rte South Bckslope N Rte, kg N h b b 57.6 b 0.72 b 0.81 b 0.88 b c 51.0 c 0.66 b 0.77 b 0.86 b c 49.1 cd 0.70 b bc c 46.8 d 0.65 b c Seeding Rte, seeds m b b b b b b c N Rte <.0001 < <.0001 Seeding Rte <.0001 N Rte*Seeding Rte Gw/Ns: N Use Efficiency; Gw/Nt: N utiliztion efficiency; Nt/Ns: N uptke efficiency; Nt/Nv: vilble N uptke efficiency; Nv/Ns: N retention efficiency. Within columns, mens followed by the sme letter re not significntly different t the 10% level. 82

102 Tble 3.5. Nitrogen nd seeding rte effect on nitrogen use efficiency nd components for soft white winter whet by lndscpe for Lndscpe nd Tretment Gw/Ns Gw/Nt NtNs NtNv Nv/Ns North Bckslope N Rte, kg N h b b 0.81 bc b b 0.85 b 0.88 b c 43.1 b 0.64 c 0.84 bc 0.77 c c 42.4 b 0.57 c 0.77 c 0.75 c Seeding Rte, seeds m b 44.0 b b b 44.9 b b b 46.3 b b N Rte <.0001 <.0001 < <.0001 Seeding Rte N Rte*Seeding Rte Footslope N Rte, kg N h b b b bc bc bc cd bc c d c c Seeding Rte, seeds m b b b b b b b b b N Rte < < <.0001 Seeding Rte N Rte*Seeding Rte South Bckslope N Rte, kg N h b 46.2 b 0.44 b b b 50.7 b 0.49 b b b 48.6 b 0.44 b b b 45.1 b 0.42 b b Seeding Rte, seeds m b b b N Rte Seeding Rte N Rte*Seeding Rte Gw/Ns: N Use Efficiency; Gw/Nt: N utiliztion efficiency; Nt/Ns: N uptke efficiency; Nt/Nv: vilble N uptke efficiency; Nv/Ns: N retention efficiency. Within columns, mens followed by the sme letter re not significntly different t the 10% level. 83

103 Tble 3.6. Person correltion coefficients between surfce soil vilble wter (0-90-cm) t nthesis nd select vribles for the 2011 nd 2012 winter whet hrvest yers. Field Correltion coefficient nd probbility by Lndscpe Vrible North Bckslope Footslope South Bckslope r p-vlue r p-vlue r p-vlue 2012 n Subsurfce Avil. Wter, cm < Biomss, kg h < < <.0001 GWNs < GwNt NtNs < NtNv NvNs < n Subsurfce Avil. Wter, cm < <.0001 Biomss, kg h < <.0001 GWNs GwNt <.0001 NtNs NtNv NvNs Gw/Ns: N Use Efficiency; Gw/Nt: N utiliztion efficiency; Nt/Ns: N uptke efficiency; Nt/Nv: vilble N uptke efficiency; Nv/Ns: N retention efficiency. Strength of reltionship defined s: 0.00 to 0.19, very wek; 0.20 to 0.39, wek; 0.40 to 0.59, moderte; 0.60 to 0.79, strong; nd 0.80 to 1.00, very strong. 84

104 Avilble N uptke efficiency (Nt/Nv) seeds m seeds m seeds m seeds m -2 N Rte, kg h -1 Over All Lndscpes Avilble N Uptke Efficiency (Nt/Nv) N Rte, kg h -1 South Bckslope 80 seeds m seeds m seeds m seeds m Figure 3.1. Interction plots for significnt N rte by seed rte effect on vilble N uptke efficiency (p =0.0187) observed in 2012 winter whet plots t Cook Agronomy Frm, ner Pullmn, WA. Dt re mens over north bckslope, footslope, nd south bckslope lndscpe positions (top) nd for the south bckslope (bottom). 85

105 North Foot South Aboveground Biomss t Anthesis, kg h c c d bc bc cd b bc bc b b b d b b b North Foot South North Foot South Avilble Wter in Surfce 90-cm t Athesis, cm b b b bc c e b b b North Foot South North Foot South Avilble Wter in 90 to 150 cm t Athesis, cm c b b bc bc c c f N Rte, kg h-1 North Bckslope Footslope South Bckslope Seeding rte, seeds m-2 Figure 3.2. Nitrogen nd Seed rte effect on winter whet boveground biomss, vilble wter in the surfce 0 to 90-cm, nd vilble wter in the subsurfce 90 to 150-cm t nthesis for north, foot, nd south slope position in Within lndscpe, mens followed by the sme letter re not significntly different t the 10% level. 86

106 North Foot South North Foot South Anthesis Biomss, kg h-1 Avilble Wter in Surfce 90cm t nthesis, cm d c b c c bc b b b b b c b b c d b b b e f b b b b North Foot South North Foot South North Foot South Avilble Wter in cm t nthesis, cm b c b b N Rte, kg h Seed Rte, seeds m-2 North Bckslope Footslope South Bckslope Figure 3.3. Nitrogen nd Seed rte effect on winter whet boveground biomss, vilble wter in the surfce 0 to 90-cm, nd vilble wter in the subsurfce 90 to 150-cm t nthesis for north, foot, nd south slope position in Within lndscpe, mens followed by the sme letter re not significntly different t the 10% level. 87

107 CHAPTER FOUR DEVELOPING NITROGEN USE EFFICIENCY PERFORMANCE CRITERIA TO EVALUATE SITE- SPECIFIC MANAGEMENT OF WHEAT. ABSTRACT Though comprehensive reviews on NUE exist, ssessment nd decision support for evluting the role of site-specific mngement to improve NUE in the Plouse region re insufficient. The min objective ws to develop performnce clssifiction for winter whet (Triticum estivum L.) bsed on NUE criteri nd ssess the utility of the clssifiction s n evlution tool. A dichotomous key ws developed to seprte whet performnce into five clsses bsed on N utiliztion efficiency (Gw/Nt), N uptke efficiency (Nt/Ns) nd NUE (Gw/Ns) criteri using regionl soft white winter whet fertility guides. Dt from three yers of lndscpe by N rte by seeding rte studies (n=605) were clssified ccording to the criteri. Performnce Clss 1 represents sitution where whet mngement strtegies were well suited to the environmentl conditions nd occurred in 16% of the observtions. Performnce Clsses 2 through 5 represent situtions where site-specific mngement strtegies might improve crop performnce nd idelly enhnce NUE. Performnce Clss 2 represented conditions where the N supplied ws not dequte to rech mximum yield resulting in the highest NUE (40 kg kg -1 ). Performnce Clss 3 ws chrcterized by the lowest men protein concentrtion (83 g kg -1 ) nd low grin yield (4.70 Mg h -1 ) reltive to Clsses 1 nd 2. Performnce Clss 3 hd the highest Gw/Nt (56 kg kg -1 ) but the lowest Nt/Ns (36%) resulting in n overll NUE of 21 kg kg -1. The reltively high grin protein (103 g kg -1 ), low HI (0.40) nd low N utiliztion efficiency (38 kg kg -1 ) in Clss 4 indicted medium evidence for hying-off. 88

108 Performnce Clss 5 ppered to be limited by n inbility to compenste for low plnt popultion nd low N vilbility due to wter-stress. Clss 5 hd the highest verge protein (107 ± 14 g kg -1 ) nd the lowest verge yield (3.97 Mg h -1 ) nd NUE (14 kg kg -1 ) compred to the other performnce clsses indicting high evidence for hying-off. The NUE-bsed performnce clssifiction ws helpful in identifying environmentl nd/or mngement conditions contributing to low or high NUE nd hs the potentil to be used with precision frming technologies such s remote sensing, on-combine yield monitors nd grin protein sensors to id on-frm evlution nd decisions. INTRODUCTION Improving the efficiency with which nitrogen (N) fertilizers re used in cropping systems hs the potentil to ddress environmentl concerns while lso providing economic benefit to griculturl producers. Cropping systems tht more effectively use N cn reduce costs ssocited with N fertilizer inputs nd minimize off site impcts ssocited with nitrte contmintion of qutic systems (Huggins nd Pn, 1993; Keller et l., 2008). Agriculturl mngement prctices to improve N use efficiency tend to be region nd cropping system specific (Cssmn, 1999; Dobermn, 2007). This is due in lrge prt to the interction of environmentl conditions nd sptiotemporl vribility tht impct the mount nd timing of N vilbility, N loss, nd crop N uptke. Evlution of these drivers is needed in order to identify pproprite mngement strtegies to improve the NUE of cropping systems. Sitespecific N fertilizer mngement (otherwise known s vrible rte) hs been considered one of the most prcticl strtegies for improving griculturl NUE nd reducing N loss to unintended 89

109 portions of the environment (Cssmn et l., 2002; Robertson nd Vitousek, 2009). However, doption of site-specific mngement requires ccurte knowledge of the vribility in soil properties relted to N cycling coupled with knowledge of crop response to this vribility. Lrge rnges in whet grin yield, yield qulity, nd NUE (4 to 34 kg kg -1 ) hve been reported within fields nd yers in the Plouse region (Sowers et l., 1994; Fiez et l., 1995; Huggins et l., 2010). Mnging this yer-to-yer nd within field vribility continues to generte interest in vrible rther thn uniform rtes of griculturl inputs (Huggins nd Pn, 1993). Nitrogen use efficiency nd N cycle processes re strongly influenced by the interction of environmentl conditions nd mngement prctices. Environmentl fctors most relted to vribility in NUE include N supply, soil temperture, timing nd mount of precipittion, nd soil moisture (Dobermn, 2007; Hwkesford, 2012). Mngement influences on NUE might include N fertilizer source, timing nd mount of N pplied, tillge nd crop rottion (Dobermn, 2007). Nitrogen use efficiency hs lso been shown to vry by crop nd mong vrieties indicting genetic influence on NUE (Dobermn, 2007; Hwkesford, 2012). Plnt genetic fctors relted to NUE include trits influencing the efficiency in which vilble N supplies re tken up nd utilized by the crop to produce biomss nd grin (Hwkesford, 2012). Genetic x environment x mngement interctions on yield nd crop performnce (e.g., NUE) underscore the importnce of regionl, if not field scle, evlutions tht incorporte locl mngement prctices, vribility in environmentl conditions nd crop response to these fctors (Cssmn, 1999; Dobermn, 2007; Huggins et l., 2010). 90

110 Mnging inputs to optimize grin yield-protein-nue reltionships requires evlution on site-specific bsis nd grower-oriented decision support tools for ssessing if site-specific mngement strtegies llowed producers to meet production, environmentl, nd economic gols. Though comprehensive reviews on NUE exist, ssessment nd decision support relevnt to site-specific N mngement re insufficient (Cssmn et l., 2002; Dobermn, 2007). The overll lck of frm scle dt on N dynmics nd NUE contributes to the scrcity of decision support tools to ssist with site-specific mngement decisions (Snyder nd Bruulsem, 2007). This is prticulrly importnt for the Plouse region of the PNW given the high sptil nd temporl vribility in grin yield, qulity nd NUE (Huggins, 2010). The gol of this reserch ws to develop n evlution tool for soft white winter whet performnce tht links sitespecific mngement with gronomic gols. The objectives were to (i) develop performnce clssifiction for whet bsed on NUE criteri; (ii) ssess performnce clssifiction using three yers of dt from lndscpe by N rte by seeding rte plot studies; nd (iii) identify soil nd crop physiologic properties useful for prediction of site-specific NUE performnce. METHODS Field plot trils from the 2010, 2011 nd 2012 winter whet hrvest yers were used to evlute lndscpe specific N fertilizer nd seeding rte effects on NUE, boveground biomss t nthesis nd vilble soil wter content t nthesis (Appendix 1). A rndomized complete block, split plot design with N fertilizer rte (NR) s the min plot nd seeding rte (SR) s the subplot were employed cross different lndscpe positions t the Cook Agronomy Frm (CAF), ner Pullmn, WA in ech yer (Appendix 2). For 2010, only the N rte experiment with uniform 91

111 plnting density (i.e., study 3) ws used. The seeding rte tretments were designed to mnipulte the production nd survivl of winter whet tillers nd provide rnge in the number of spikes per unit re mong different lndscpe positions Nitrogen Rte Experiment with Uniform Plnt Density Soft white winter whet ( OR102 ) ws plnted in pired rows on 30 cm (12 in) centers using no-till drill (Horsh-Anderson) equipped with hoe type openers. An N rte plot scle experiment in the north, summit, nd south slope lndscpe positions ws initited in the spring of 2010 within lrger field-scle N rte study. The field ws seeded t uniform rte of 240 seeds m -2 nd N fertilizer ws pplied t 0, 48, 76, nd 104 kg N h -1 using ure mmonium nitrte (32-0-0) in October of There were four replictes for north nd south slopes nd two replictes for the summit position. Replictes for the summit position were limited by the smll size of the summit lndscpe position for this prticulr field t CAF. The previous crop ws hrd red spring whet ( Hnk ) nd 2012 N Rte x Seed Rte Studies Field plots were seeded nd fertilized on 19 cm (7.5 in) row spcing using Fbro notill double disk plot drill with totl min plot size of 35 m 2 nd subplot size of 8.75 m 2. Nitrogen fertilizer (dry ure, ) ws estblished s the min plot nd bnd pplied below the seed t plnting t rtes of 0, 40, 80, 120, nd 160 kg N h -1. Plnt popultion nd spike density differences were estblished within ech NR strip by seeding t 80, 165, 250, nd 335 seeds m -2. Soft white winter club whet ( Chukr ) ws plnted on October 13 in both 2011 nd Seed weight nd kernels per pound were determined ech yer to clculte the mount 92

112 of seed weight required to chieve the desired seeding rtes. The previous crop ws grbnzo bens (Cicer rietinum, Sierr ). Components of N Use Efficiency Nitrogen use efficiency nd components were determined from grin yield (Gw), grin N (Ng), boveground plnt N (Nt), pplied N (Nf), nd pre- nd post-hrvest root zone soil inorgnic N (153-cm), Nr nd Nh, respectively. In this reserch, NUE is clculted s the hrvested grin yield (Gw) divided by N supply (Ns) where the N supply includes soil nd fertilizer derived N sources (Huggins nd Pn, 2003). Nitrogen use efficiency nd components terminology re summrized in Appendix A-7. Following Huggins et l. (2010), NUE ws prtitioned into the following components: N retention efficiency (Nv/Ns), vilble N uptke efficiency (Nt/Nv), nd N utiliztion efficiency (Gw/Nt). The N uptke efficiency (Nt/Ns) nd vilble N use efficiency (Gw/Nv) cn be determined from these components. The N uptke efficiency is the boveground N divided by the N supply nd the N utiliztion efficiency is the grin yield divided by the boveground plnt N. Nitrogen use efficiency cn lso be determined from the N fertilizer use efficiency (Gw/Nf) nd the N relince index (Nf/Ns). Performnce Clssifiction A dichotomous key ws developed to seprte whet performnce into five clsses bsed on N utiliztion efficiency (Gw/Nt), N uptke efficiency (Nt/Ns) nd NUE (Gw/Ns) (Figure 4.1). Performnce clsses 1 through 3 re where whet chieved n N utiliztion efficiency of 45 or greter. Performnce Clsses 4 nd 5 represent conditions where the N utiliztion efficiency gol of 45 ws not chieved. Within the N utiliztion efficiency criteri, performnce 93

113 ws further seprted using n N uptke efficiency threshold of 50%. The N utiliztion efficiency criteri of 45 ws selected s performnce gol bsed on the drylnd soft white winter whet fertilizer guide unit N requirement of 45 g N kg -1 grin (2.7 lbs N bu -1 ) which ssumes n N uptke efficiency of t lest 50% (Koenig, 2005). From the UNR, which is the inverse of NUE, it ws derived tht the generlly ccepted NUE for soft white winter whet in the region is 22 kg grin per kg of N supplied (Koenig, 2005). Performnce Clsses 1, 2 nd 4 re where N uptke efficiency is greter thn or equl to 50% nd Clsses 3 nd 5 where N uptke efficiency is below 50%. A NUE of greter thn or equl to 30 kg grin per kg N supplied ws used to distinguish high NUE performnce tht rises from N fertilizer ppliction rtes below tht needed to chieve the mximum yield gol. This llowed instnces of high NUE to be further seprted into conditions where yield gol gols were either met nd exceeded or unrelized s result of insufficient N supply. Performnce Clss 1 is where the Gw/Nt is greter thn 45 nd Nt/Ns ws greter thn 50% but NUE ws less thn 30 nd mximum yield ws obtined. In Performnce Clss 2 the Gw/Nt ws lso greter thn 45 nd the Nt/Ns bove 50% but the NUE ws greter thn or equl to 30. Performnce Clss 2 represents conditions where the N supply ws not dequte to obtin mximum grin yield. Tht is, the N supply ws too low to support the yield gol for the conditions. Sttistics A clssifiction scheme ws developed bsed on NUE performnce criteri. Discriminnt nlysis ws used to predict clss membership from suite of NUE components, relted soil N 94

114 cycling, nd soil vilble wter metrics. A stepwise selection method within the STEPDISC procedure of SAS (SAS 9.4, SAS Inst., 2012) procedure ws used to ssist in identifying key vribles for use in differentiting performnce clssifiction in subsequent discriminnt nlysis. A stepwise entry of 0.4 nd sty of 0.05 ws used. The PROC DISCRIM function (SAS 9.4, SAS Inst., 2012) ws used to predict clss membership from combintion of selected predictor vribles which resulted in the lest mount of misclssifiction. RESULTS & DISCUSSION The NUE-bsed performnce clssifiction criteri ws used to evlute soft white winter whet performnce with respect to Gw, grin protein concentrtion, nd NUE cross ll dt points for the three site yers of this study (605 dt points in totl). Assessments of NUE included mesurements of severl NUE indices in order to dignose nd evlute field-scle crop performnce s well s the drivers of vrition in yield-nue reltionships (Huggins nd Pn, 1993; Dobermn, 2005; Dwson et l., 2008). Grin Yield, Protein, nd NUE Grin yield rnged from 1270 to kg h -1 cross ll dt points indicting the lrge rnge in yield gol cross lndscpe, N rtes nd seeding rte combintions (Fig. 4.2). There ws no cler trend between grin protein concentrtion nd grin yield (Fig. 4.2). As N supply incresed, the N in the grin nd grin yield tended to increse but the rnge in response ppered to differ mong Performnce Clsses (Fig. 4.2b nd 4.2c). Grin yield increses were ssocited with increses in Ng (Fig. 4.2d). Over ll plots nd site yers, the NUE rnged from 7.8 to 64 kg kg -1 with n verge of 28.6 kg kg -1 (dt not shown). Considerble vribility in 95

115 grin protein, yield, nd NUE hs been reported previously within crop fields nd mong crop yers in the Plouse region (Fiez et l., 1994b; Fiez et l., 1995; Huggins et l., 2010b). The NUE of soft white winter whet hs been reported to rnge from 15 to 33 kg kg -1 cross Plouse fields (Sowers et l., 1994; Fiez et l., 1995). Sowers observed NUE to rnge from 18 to 24 kg kg - 1 for soft white winter whet cross two field sites with split N or ll fll pplied N fertilizer. Fiez et l. (1995) reported NUE to rnge from kg grin per kg -1 N supply for soft white winter whet cross four different lndscpe positions over two growing sesons. The lrger rnge in NUE observed in this study, s compred to others in the region, is ttributed to the rnge in wether conditions (Appendix 3) nd the inclusion of seeding rte tretments in combintion with the N rte tretments. Nitrogen Utiliztion Efficiency Nitrogen utiliztion efficiency (Gw/Nt) is the efficiency with which the plnt produces grin, given the mount of boveground plnt N (Huggins nd Pn, 1993; Fiez et l., 1995). Across ll plot dt, the Gw/Nt rnged from 22 to 75 kg kg -1 with n verge of 49 kg kg -1 (Fig. 4.3). There ws no cler trend between grin protein concentrtion nd NUE (Fig. 4.3). However, Gw/Nt ws negtively correlted with grin protein (r 2 =0.74) (Fig. 4.3b). The negtive reltionship between Gw/Nt nd grin protein concentrtion re in greement with the findings of Huggins et l. (2010b). Grin yield tended to increse with n increse in boveground N (Nt), but vried t equivlent levels of Nt, leding to the wide rnge in Gw/Nt (Fig. 4.3c). The proportion of boveground N mobilized to the grin, kg Ng per kg Nt, is referred to s the N hrvest index (NHI). There ws liner increse in Ng s Nt incresed cross ll 96

116 performnce clsses (r 2 =0.90) (Fig. 4.3d). From the slope of the liner regression it ws observed tht 70% of the Nt ws mobilized to the grin. The rnge in NHI vlues observed in this study re similr to the 70 to 77% rnge reported by Huggins nd Pn (2003) for soft white winter whet. Reltively constnt NHI indicte tht N tken up by whet under Plouse cropping systems follows predicble physiologicl N use efficiency (Huggins et l., 2010). Nitrogen Uptke Efficiency Nitrogen uptke efficiency (Nt/Ns) is the totl boveground plnt N divided by the totl N supply, kg Nt per kg N supply. It is vluble performnce criteri s it describes the efficiency with which the crop cquires N from soil nd fertilizer sources (Huggins nd Pn, 1993; Fiez et l., 1995). Across ll dt points the Nt/Ns rnged from 18 to 98% with n verge of 58% (Fig. 4.4). There ws no cler trend between grin protein concentrtion nd Nt/Ns (Fig. 4.4). The rnge in Nt/Ns ws greter thn the 40 to 70% rnge reported in plot reserch by Huggins et l., (2010) for hrd red spring whet. Mnging boveground N ccumultion (i.e., Nt) to simultneously chieve Gw nd protein gols is dependent on the vilbility of N supply (Nv), how efficiently the crop cquires N from vilble sources (Nt/Nv) nd mtching the N supply with other fctors such s wter stress, root limiting conditions or pest pressure tht impct N uptke (Pn nd Hopkins, 1991). To sses nd further dignose field conditions or mngement strtegies leding to low Nt/Ns, the Nt/Ns ws broken out into vilble N uptke efficiency (Nt/Nv) nd N retention efficiency (Nv/Ns). Avilble Nitrogen Uptke Efficiency nd Nitrogen Retention Efficiency Avilble N uptke efficiency is the boveground plnt N divided by the vilble N (kg 97

117 kg -1 ) nd cn be used to evlute how much of the vilble N ws tken up by the crop. The verge Nt/Nv ws 81% with rnge of 29 to 99 % cross ll dt points (dt not shown). Aboveground plnt N (i.e., Nt) incresed s the N supply nd N vilbility incresed (Fig. 4.4b nd 4.4c). Previous reserch reported n verge Nt/Nv of 78% for soft white winter whet (Sowers et l., 1994). Huggins et l. (2010) found Nt/Nv to rnge from 46 to 90% for plot dt nd from 25 to 85% in field tril for hrd red spring whet. Low Nt/Nv could result from poor mtch of vilble N with crop N demnd (Huggins et l., 2010). High Nt/Nv cross dt points nd mong Performnce Clsses indicted tht the winter whet plnts were reltively efficient t tking up sources of vilble N. Therefore, N retention efficiency (Nv/Ns) hd reltively greter impct on vilbility of N, Nt/Ns nd subsequently NUE. Nitrogen retention efficiency is the rtio of vilble N to the N supply (Nv/Ns). It describes how much of the N supply ws vilble to the plnt nd cn be used to ssess N loss. Low Nv/Ns indictes N loss, while high Nv/Ns coupled with low Nt/Nv, indictes poor mtch between vilble N nd crop N demnd (Huggins nd Pn, 2003; Huggins et l., 2010). The Nv/Ns rnged from 26 to 100% with n verge of 72% over ll dt points (dt not shown). The vilbility of N tended to increse s N supply incresed (Fig. 4.4d). Huggins et l. (2010) found Nv/Ns to rnge from 70 to 98% (verge of 82%) nd from 20 to over 100% (verge of 50%) for plot nd field reserch, respectively. Nitrogen retention efficiencies bove 100% cn be ttributed to redistribution of soil nitrte or mesurement nd smpling errors (Huggins et l., 2010). These results indicte tht low Nv/Ns rther thn Nt/Nv ply lrger role in regulting NUE thn N utiliztion efficiency. Therefore, vribility in N loss to completing 98

118 pthwys is limiting the vilbility of the N supply nd subsequently reducing NUE s lso observed by Fiez et l., (1995). Nitrogen loss pthwys cn include gseous N losses, leching nd biologicl immobiliztion (Huggins nd Pn, 1993; Huggins et l., 2010). The high grin protein concentrtions ssocited with low Gw/Nt indicte tht environmentl or mngement limittions on yield cn lso be importnt in reducing Nt/Ns. The low Gw/Nt or Nt/Ns observed my be relted to N loss (low Nv/Ns), over or under fertiliztion (N supply), below optiml plnt popultion (biomss nd N sink cpcity) or wter-stress induced N deficiency (vilble wter). Previous reserch in the Plouse hs shown tht vrible rte N ppliction mngement hs the potentil to improve NUE (Mull et l., 1992; Fiez et l., 1994). However, dvncing the use of site-specific mngement to improve NUE requires grower-oriented nd field-scle understnding of environmentl nd mngement impcts on N cycle processes nd crop performnce (Run nd Johnson, 1999; Cssmn et l., 2002; Pn et l., 2007). Performnce Clssifiction: Evlution Tool for Assessing Ecophysciologicl Controls on NUE Performnce Clss 2 hd the gretest number of dt points (229) followed by Clss 4 (114) > Clss 3 (112) > Clss 1 (99) > Clss 5 (51) (Tble 4.1). Performnce Clss 1 represents sitution where soft white winter whet mngement strtegies re well suited to the environmentl conditions nd only occurred in 16% of the observtions. Performnce Clsses 2 through 5 represent situtions where site-specific mngement strtegies might improve crop performnce nd idelly enhnce NUE. Performnce Clss 1 99

119 Performnce Clss 1 exceeded the minimum ccepted NUE of 22 kg grin kg N -1 nd exhibited high verge yield (6.04 ± 1.47 Mg h -1 ) (Tble 4.1). This Clss ws chrcterized by n verge grin protein concentrtion of 92 g kg -1 tht rnged from 71 to 110 g kg -1. In Performnce Clss 1 the vilble N uptke efficiency ws 0.81 nd the N retention efficiency 0.67 (Tble 4.1). This produced n verge N uptke efficiency of 54% nd combined with n N utiliztion efficiency of 49 kg kg -1 resulted in n verge NUE of 26 kg kg -1. This Clss ws chrcterized by moderte N supply (228 ± 51 kg N h -1 ) nd reltively high ctul plnt density (187 ± 97 plnts m -2 ) (Tble 4.1). Overll, the performnce of this clss indicted mngement ws well suited to the environmentl conditions. It indictes tht incresing the trget NUE from 22 to 26 kg kg -1 my be fesible. A little under hlf of Clss 1 occurred in 2011 (46%) compred to 34% in 2012 nd 19% in 2010 (Fig. 4.5). There were similr instnces of Clss 1 in north nd south bckslope positions (37 nd 39%) s compred to footslope positions (23%) (Fig. 4.5b). The 120 kg N h -1 nd 246 to 250 seeds m -2 N nd seed rte hd the gretest frequency of occurrences (Fig. 4.5c nd 4.5d) nd these represent the business s usul N nd seed rte t CAF. The instnces of Clss 1 in different lndscpe positions nd t lower N nd seed rte tretments thn norml indicte tht vrible rte N nd seed hve the potentil to improve NUE without compromising yield. Performnce Clss 2 Clss 2 represented conditions where the N supplied ws not dequte to rech mximum yield for the environmentl conditions nd greter proportion of the N supply ws 100

120 tken up by the whet crop s compred to the other clsses (Figure 4.4). In Performnce Clss 2 the vilble N uptke (0.85), N retention (0.88) nd N utiliztion efficiency (53) were high resulting in the highest NUE (40 kg kg -1 ) mong the Performnce Clsses (Tble 4.1). This clss exhibited the highest verge yield (6.21 ± 1.48 Mg h -1 ) with the lowest Ns (164 ± 54 kg N h - 1 ). Performnce Clss 2 hd men protein concentrtion of 87 g kg -1 rnging from 64 to 107 g kg -1. The high N uptke efficiency of Clss 2 ws ssocited with the lowest verge N fertilizer ppliction rte (51 kg N h -1 ) nd reltively high plnt density (203 ± 90 plnts m -2 ) s compred to the other Clsses (Tble 4.1). Suboptiml N fertiliztion led to n insufficient N supply reltive to the yield gol yet incresing the N fertilizer rtes would likely reduce NUE. It is interesting to note tht Clss 2 ws chrcterized by high vilble wter t tillering (28 cm), high consumptive wter use (34 cm), nd high wter use efficiency (Tble 4.3). Grin yield could be incresed by supplying greter mount of N (i.e., higher N fertiliztion rte) but greter yield response would be chieved t the expense of lower NUE. A mjority of Clss 2 occurred in the 2011 site yer (60%) nd were observed to occur t similr frequency in north (38%), footslope (28%), nd south bckslope (34%) positions (Fig. 4.5 nd 4.5b). Sixty-one percent of occurrences were t N rtes of 48 kg N h -1 or below nd 83% t or below 80 kg N h -1 (Fig. 4.5c). In most cses, suboptiml N fertiliztion, especilly in the wet wether conditions of 2011, led to n insufficient N supply reltive to the high yield gol (dt not shown). Incresing the N rte to simultneously chieve yield gol is likely to lower the verge NUE of the Clss but would still be expected to meet the minimum trget of 22 kg kg -1. Spring 101

121 top-dress pplictions of N for situtions leding to Performnce Clss 2 might be n lterntive N mngement strtegy to chieve mximum yield gol without lrge reductions in NUE. Performnce Clss 3 Performnce Clss 3 ws chrcterized by the lowest men protein concentrtion of 83 g kg -1 rnging from 64 to 120 g kg -1 (Tble 4.1). Reltive to Clsses 1 nd 2, Clss 3 exhibited reltively lower grin yield (4.70 ± 1.00 Mg h -1 ) nd n N supply (235 ± 53 kg h -1 ) comprble to Clss 1 (228 ± 51 kg h -1 ). Clss 3 hd the highest N utiliztion efficiency (56 kg kg -1 ) but the lowest N uptke efficiency (36%) tht resulted in n overll NUE of 21 kg kg -1 for this Clss which is slightly below the 22 kg kg -1 performnce gol. Performnce Clss 3 ws chrcterized by n verge vilble N uptke efficiency of 74% nd N retention efficiency of 0.51 kg kg -1. In ddition, Clss 3 hd the lowest Nt compred to ll the Performnce Clsses (Tble 4.1) nd the lowest totl biomss t mturity (Tble 4.2). Approximtely 50% of Clss 3 occurred in 2012 followed by 2011 (34%) (Fig. 4.5). The predominnt lndscpe positions where Clss 3 occurred included footslope (54%) nd south bckslope (38%) lndscpe positions (Fig. 4.5b). Performnce Clss 3 occurred over rnge of N nd seed rte tretments (Fig. 4.5c nd 4.5d). Nitrogen fertilizer rtes bove 120 kg N h -1 represented 43% of occurrences (Fig. 4.5c) nd seeding rtes bove 240 seeds m -2 ccounted for 46% of occurrences (Fig. 4.5d). Overll, the low N uptke efficiency ppers to be driven by low vilbility of the N supply (i.e., low Nv/Ns) tht ws ssocited with low biomss, the lowest spikes m -2 nd low N uptke (i.e., Nt) s compred to the other clsses. This indicted tht under the conditions of Clss 3 compenstion mong yield components limited N uptke nd N loss limited N vilbility tht 102

122 combined resulted in the lowest Nt/Ns. There ws evidence of N loss s result of concentrted flow nd lso shllow soil in the footlslope compred to the other lndscpe positions tht would hve contributed to N loss. In the south bckslope, positionl unvilbility of N due to root restrictive soil lyers my hve reduced N uptke. Given the high Gw/Nt in Clss 3, mngement should be trgeted tht would increse N vilbility s well s N uptke. This would include split N ppliction between fll nd spring to reduce N loss nd subsequently increse N uptke. Performnce Clss 4 Performnce Clss 4 hd n verge grin yield of 5.56 ± 1.63 Mg h -1 nd high grin protein concentrtion (103 ± 27 g kg -1 ) (Tble 4.1). Clss 4 ws chrcterized by high N retention (72%) nd vilble N uptke (81%) efficiencies resulting in n Nt/Ns greter thn 50%. The N utiliztion efficiency ws low (38 kg kg -1 ) leding to n verge NUE of 23 kg kg -1 which slightly exceeds the minimum NUE trget of 22 kg kg -1. The winter whet under Clss 4 is therefore ble to tke up vilble N nd the N supply ws dequte but grin yield did not increse reltive to crop N uptke. Performnce Clss 4 ws chrcterized by reltively lower ctul plnt density (155 ± 73 plnts m -2 ) but the highest biomss t mturity (14,031 kg h -1 ) indicting compenstion mong yield components (Tbles 4.1 nd 4.3). This is supported by the reltively higher tillers per plnt nd spikes m -2 for Clss 4 s compred to the other Clsses (Tble 4.3). However, the reltively low HI (0.40) indictes tht the erly vegettive biomss set n unrelisticlly high yield gol for the site conditions tht represent Clss 4. The high biomss 103

123 productions ws lso ssocited with the highest N vilbility, crop N uptke, nd N content in the grin. Overll, this indictes tht hying-off is occurring under the conditions of Performnce Clss 4 winter whet. Hying-off in cerel crops is described s grin yield reduction resulting from excessive vegettive growth tht excerbtes terminl drought during grin filling (vn Herwrden et l., 1998; Angus nd vn Herwrden, 2001). Hying-off hs been ttributed to soil wter deficit during grin filling when: (i) high levels of vilble soil N stimulte vegettive growth nd high soil wter consumption (vn Herwrden et l., 1998; Angus nd vnherwrden, 2001); nd/or (ii) high plnt popultions result in greter biomss tht increses competition for vilble wter (Fischer nd Kohn, 1966). The lrge occurrence of Clss 4 in the dry conditions of 2010 (50%) support tht the Clss 4 criteri re dignostic of the hying-off phenomenon. In Performnce Clss 4 the overll NUE performnce gol ws met but improvements to Gw/Nt would enhnce NUE nd likely yield s well. Reductions in N fertilizer ppliction rtes to reduce N stimulted vegettive biomss production nd void hying-off should be considered for this Clss. In ddition, pre-plnt soil smpling following low yielding, high N fertilized crop might reduce high N vilbility to better mtch yield gol, biomss nd N uptke. Furthermore, N pplied in excess of the yield gol for Clss 4 resulted in lmost hlf of the dt points exceeding the 105 g kg -1 mrket preference for soft white whet (Ro et l., 1993; Morris, 2004). Performnce Clss 5 104

124 Performnce Clss 5 hd the highest verge protein (107 ± 14 g kg -1 ) nd the lowest verge yield (3.97 ± 0.73 Mg h -1 ) compred to the other performnce clsses. Field or mngement conditions resulted in the lowest NUE (14 kg kg -1 ) s result of both low Gw/Nt nd low Nt/Ns. Clss 5 ws observed to hve reltively high vilble N uptke efficiency (78%) but low N retention efficiency (49%) resulting in n N uptke efficiency of 38% (Tble 4.1). The nitrogen utiliztion efficiency of 38 kg kg -1 ws lso below the performnce criteri of 45 kg kg -1. A lrge mount of the N supply cme from residul N (130 ± 37 kg pre-plnt N h -1 ) resulting in the highest N supply compred to the other Performnce Clsses (Tble 4.1). Clss 5 hd reltively low boveground biomss (10,811 ± 2,162 kg h -1 ) tht ws slightly higher thn Clss 3 (10,773 ± 2,192 kg h -1 ) nd the lowest hrvest index (0.37) nd test weight (73.2 kg hl - 1 ) of ll the Performnce Clsses (Tbles 4.2 nd 4.3). A mjority of Clss 5 dt points were from the drier thn norml 2010 site yer (Fig. 4.5) nd reltively drier south bckslope nd summit lndscpe positions (Fig. 4.5b). Nitrogen loss leding to low vilbility of the N supply in this cse would be ttributed to greter losses due to immobiliztion or denitrifiction. Performnce Clss 5 occurred cross rnge of N nd seed rte tretments. On verge, Clss 5 hd the lowest ctul plnt density (149 ± 62 plnts m -2 ), lowest vilble wter t tillering (19.5 ± 5.4 cm) nd the lowest WUE (149 ± 49 kg h-cm - 1 ) s compred to the other Clsses. From this it ppered tht Clss 5 grin yield nd N uptke were limited by n inbility to compenste for low plnt popultion nd low N vilbility due to wter-stress nd N losses. The low yield, high protein, low hrvest index nd low test weight supports tht hying-off occurred in Clss 5 (vn Herwrden et l., 1998). It ppered tht 105

125 Performnce Clss 5 represented conditions of high risk of hying-off nd further nlysis to link the Clssifiction criteri to the risk of hying off is recommended (Tble 2.4). Since Clss 5 ppers to occur in dry yers nd dry lndscpe positions, improving NUE should include N rte reductions to better mtch N supply to field conditions. Split ppliction of N fertilizer would llow for erly spring djustments to the N supply should conditions be wetter thn norml. Higher seed rtes would not be expected to increse N uptke or yield given the low vilble wter resources observed under Performnce Clss 5. Assessing the Performnce Clssifiction s Post-Hrvest Evlution Tool The NUE-bsed performnce clssifiction ppered to be helpful in identifying environmentl nd/or mngement conditions contributing to low or high NUE. Under the existing criteri, Performnce Clsses 1, 2 nd 4 re more esily interpreted while Clsses 3 nd 5 pper to include soil or crop physiologicl processes tht re more difficult to scertin. Overll, the performnce clssifiction hs the potentil to be used s n evlution tool for ssessing NUE while lso incorporting grin yield nd grin qulity gols. Additionl NUE components nd indices could be considered to further dignose nd evlute crop performnce within nd mong the existing performnce clssifiction. This might include the N blnce index (Ng/Nf), N loss index, vilble N uptke efficiency (Gw/Nv), nd hrvest index (Gw/boveground biomss). Additionl yield qulity indictors, such s test weight, or yield components should lso be considered to further dignose conditions leding to hyingoff. 106

126 The trends in Gw/Nf nd Ng/Nf were similr to those for Nt/Ns nd these components provide more prcticl proxy for on-frm ssessment of N uptke efficiencies (Tbles 4.1 nd 4.2). It ws lso observed tht lower consumptive wter use ws ssocited with low Nt/Ns (i.e., Clss 3 nd 5). Avilble N use efficiency (Gw/Nv) ws good seprtor of N utiliztion efficiency s opposed to NUE. Performnce Clsses 4 nd 5 hd lower Gw/Nv (31 nd 30 kg kg - 1 ) compred to clsses 1, 2, nd 3 (40, 45, nd 41 kg kg -1 ) (Tble 4.2). This metric of NUE hs the dvntge of looking t the bility of the plnt to produce yield from the vilble N portion of the N supply nd should be considered in future refinements of this pproch. Prediction of Performnce Clsses Discriminnt nlysis ws used to predict clss membership from suite of NUE components, relted soil N cycling processes, nd soil vilble wter metrics. Tretments of field, lndscpe, N fertilizer ppliction rte nd seeding rte were included in ll discriminnt function nlysis in order to link evlution to site-specific mngement. Results indicted tht grin yield, grin protein, Ng/Nt nd Ng/Nf were the most meningful combintions of fctors in ddition to tretment tht predict performnce clssifiction t n error rte of 27% (Tble 4.4). Nitrogen fertilizer recovery efficiencies (e. g., Ng/Nf or Gw/Nf) overlook the contribution nd vilbility of ll N sources but re more esily determined with on-combine yield monitors nd protein sensors. Linking these predictive NUE components with those tht cn be used to dignose environmentl nd/or mngement drivers of crop N uptke nd utiliztion efficiency re needed to improve the utility of the Performnce Clssifiction. Future Reserch 107

127 The lck of correltion between grin yield nd protein concentrtion cross or within Performnce Clss indictes tht sptiotemporl vribility in climte, lndscpe nd soil properties my be importnt determinnts of grin yield-protein reltionships (Fiez et l., 1995; Huggins et l., 2010). Vrible rte N nd/or seed mngement bsed on this performnce clssifiction will require linkge of the temporl nd sptil vribility in NUE with lndscpe specific processes influencing the reltionship between crop growth, nutrient nd wter use efficiencies, grin yield nd qulity. Rpid in-crop ssessments of biomss nd crop N sttus using remote sensing (Eitel et l., 2014) could be linked with post-hrvest yield, grin protein concentrtion nd nitrogen use efficiency dt by mngement zones nd/or lndscpe positions. Additionl reserch employing such tools s discriminnt nlysis to identify soil nd/or crop physiologicl bsed predictors of performnce nd develop grower-oriented nd field scle decision support regrding nutrient use efficiency is needed. Future reserch to support the development of evlution tools relted to site-specific mngement should include investigtion of the environmentl, mngement or genetic controls on NUE within performnce clsses. Simple, rpid nd cost-effective evlution tools tht could be employed by growers include on-combine yield monitors coupled with grin protein sensors (Long et l., 2008). CONCLUSIONS Field scle improvements to NUE re hindered by the lck of funding nd mount of resources required to perform on-frm field-scle ssessment of environmentl nd 108

128 mngement impcts driving the tremendous sptil nd temporl vribility in NUE observe in Plouse fields. This contributes to the reltively slow doption of precision griculture principles nd technologies for enhncing field-scle nd frm-level performnce, especilly with regrd to NUE. The NUE performnce clssifiction developed in this reserch ws successful in dignosing environmentl nd N nd seed rte mngement fctors contributing to the lrge vribility in NUE s observed. Improvements to the existing criteri re needed s Performnce Clsses 1, 2 nd 4 re more esily interpreted s compred to Clsses 3 nd 5. In ddition, the performnce clssifiction hs the potentil to be grower relevnt evlution tool for ssessing NUE tht simultneously incorportes grin yield nd grin qulity gols. 109

129 REFERENCES CITED Cssmn, K.G Ecologicl intensifiction of cerel production systems: yield potentil, soil qulity, nd precision griculture. Proc. Ntl. Acd. Sci. 96: Cssmn, K.G., A. Dobermnn, nd D. T. Wlters Agroecosystems, nitrogen-use efficiency, nd nitrogen mngement. Ambio. 31(2): Dwson, J.C., D.R. Huggins, nd S.S. Jones Chrcterizing nitrogen use efficiency in nturl nd griculturl ecosystems to improve the performnce of cerel crops in lowinput nd orgnic griculturl systems. Field Crops Res. 107: Dobermn, A.R Nitrogen use efficiency Stte of the rt. Agronomy & Horticulture Fculty Publictions. Pper 316. Avilble online t ccessed 2/2/2015. Dobermn, Nutrient use efficiency mesurement nd mngement. In Fertilizer Best Mngement Prctices First Edition. Interntionl Fertilizer Industry Assocition, Pris, Frnce. pgs Fiez. T.E., B. C. Miller, nd W.L. Pn Assessment of sptilly vrible nitrogen fertilizer mngement in winter whet. J. Prod. Agric. 7(1): Fiez et l., 1994b. Winter whet yield nd grin protein cross vried lndscpe positions. Agron. J. 86: Fiez et l., Nitrogen use efficiency of winter whet mong lndscpe positions. Soil Sci Soc. Am. J. 59: Hwkesford, M.J The diversity of nitrogen use efficiency for whet vrieties nd the potentil for crop improvement. Better Crops. 96 (3): Huggins, D.R. nd W.L. Pn Nitrogen Efficiency Component Anlysis: An evlution of cropping system differences in productivity. Agron. J. 85: Huggins, D.R. nd W.L. Pn Key indictors for ssessing nitrogen use efficiency in cerelbsed groecosystems. J. Crop Production 8:

130 Huggins, D., W. Pn, nd J. Smith Yield, protein nd nitrogen use efficiency of spring whet: evluting field-scle performnce. Chpter 17 in Kruger, C., G. Yorgey, S. Chen, H. Collins, C. Feise, C. Frer, D. Grntstein, S. Higgins, D. Huggins, C. McConnell, K. Pinter, C. Stöckle Climte Friendly Frming: Improving the Crbon Footprint of Agriculture in the Pcific Northwest. CSANR Reserch Report Wshington Stte University: Keller, C.K., J.L. Smith, nd R.M. Allen-King Nitrte in tile dringe of the semirid Plouse Bsin. J. Environ. Qul. 37: Koenig, R.T Drylnd winter whet. Estern Wshington nutrient mngement guide. EB1987. Wshington Stte University. WSU Extension Publishing nd Printing. Long D.S., R.E. Engel, nd M.C. Siemens Mesuring grin protein concentrtion with inline ner infrred reflectnce spectroscopy. Agron. J. 100: Morris, C.F Grin qulity Idho whet production guide. Pg In L.D. Robertson, S.O. Guy, nd B.D. Brown (Eds.) Southern Idho Drylnd Winter Whet Guide. University of Idho BUL 827. Mull, D.J., A.U. Bhtti, M.W. Hmmond, nd J.A. Benson A comprison of winter whet yield nd qulity under uniform versus sptilly vrible fertilizer mngement. Agric. Ecosys. Environ. 38: Pn, W.L., W. Schillinger, D. Huggins, R. Koenig, nd J. Burns Fifty yers of predicting whet nitrogen requirements in the Pcific Northwest U.S.A. Ro, A.C.S, J.L. Smith, V.K. Jndhyl, R.I. Ppendick, nd J. F. Prr Cultivr nd climtic effects on the protein content of soft white winter whet. Agron. J. 85: Run, W.R. nd G. V. Johnson Improving nitrogen use efficiency for cerel production. Agron. J. 91: Robertson, G.P., P.M. Vitousek Nitrogen in griculture: blncing the cost of n essentil resource. Annu. Rev. Environ, Resour. 34: Snyder, C.S. nd T.W. Bruulsem Nutrient use efficiency nd effectiveness in North Americ: indices of gronomic nd environmentl benefit. Interntionl Plnt Nutrition Institute (IPNI) publiction

131 Sowers, K.E., B.C. Miller, nd W.L. Pn Optimizing yield nd grin protein in soft white winter whet with split nitrogen pplictions. Agron. J. 86: Vn Herwrden, A.F., G.D. Frquhr, J.F. Angus, R.A. Richrds, nd G.N. Howe Hyingoff, the negtive grin yield response of drylnd whet to nitrogen fertilizer I. Biomss, grin yield, nd wter use. Aust. J. Agric. Res. 49:

132 Tble 4.1. Averge grin yield, protein, nd N use efficiency components by performnce clss cross ll dt points. NUE Component Performnce Clss Number of points (n) Men (Std Dev.) ' N Fertilizer rte, kg h (55) 51 (49) 90 (51) 96 (50) 97 (35) Trget Plnt Density, plnts m (91) 221 (92) 206 (89) 179 (78) 183 (75) Actul Plnt Density, plnts m (97) 203 (90) 184 (85) 155 (73) 149 (62) Grin Yield, kg h (1473) 6208 (1480) 4697 (993) 5563 (1630) 3966 (726) N in Grin (Ng), kg h (26) 93 (26) 67 (16) 103 (27) 74 (14) Grin Protein, g kg (9.0) 87.4 (10.0) 82.6 (11.6) (12.0) (14.3) Aboveground plnt N (Nt), kg h (33) 119 (35) 85 (20) 148 (34) 105 (21) Totl N supply (Ns), g h (51) 164 (54) 235 (53) 252 (52) 278 (51) Avilble N (Nv), kg h (38) 141 (39) 117 (27) 180 (44) 136 (28) Gw/Ns, kg grin (kg N supply) (2) 40 (8) 21 (4) 23 (6) 14 (2) Gw/Nt, kg Gw (kg Nt) (4) 53 (6) 56 (7) 38 (5) 38 (5) Nt/Ns, kg Nt (kg N supply) (0.05) 0.75 (0.12) 0.37 (0.06) 0.59 (0.11) 0.38 (0.06) Avilble N Uptke Effic. (Nt/Nv) 0.81 (0.09) 0.85 (0.09) 0.74 (0.13) 0.81 (0.07) 0.78 (0.10) N Retention Effic. (Nv/Ns) 0.67 (0.09) 0.88 (0.12) 0.51 (0.12) 0.72 (0.15) 0.49 (0.08) Refer to tble 1 for description of N use efficiency components. Vlues in prenthesis re stndrd devition. 113

133 Tble 4.2. Additionl N use efficiency components verged by performnce clss cross ll dt points. NUE Component Performnce Clss Number of points (n) Men (Std Dev.) Residul N (Nr, pre-plnt), kg h (28.6) 59.7 (20.8) 87.6 (36.8) (42.5) (36.5) N in Soil t Hrvest (Nh), kg h (19.2) 25.0 (18.2) 32.0 (21.3) 34.0 (17.6) 31.1 (19.1) N Minerliztion, kg h (24.6) 39.2 (22.6) 44.1 (28.1) 41.2 (28.1) 40.3 (22.3) Grin N Accumultion Effic. (Ng/Ns) 0.42 (0.05) 0.59 (0.11) 0.29 (0.05) 0.42 (0.10) 0.27 (0.04) N Hrvest Index (Ng/Nt) 0.77 (0.06) 0.79 (0.05) 0.78 (0.06) 0.70 (0.07) 0.71 (0.07) Avilble N Use Effic. (Gw/Nv) 39.9 (4.97) 45.0 (6.89) 41.2 (8.73) 31.1 (6.61) 29.7 (5.35) N Fertilizer Utiliztion Effic. (Gw/Nf) 118 (151) 191 (157) 76 (90) 97 (139) 41 (14) N Relince Index (Nf/Ns) 0.43 (0.20) 0.35 (0.20) 0.42 (0.18) 0.42 (0.19) 0.39 (0.13) N Blnce Index (Ng/Nf) 1.77 (2.11) 2.76 (2.20) 1.04 (1.17) 1.89 (2.87) 0.77 (0.35) Vlue in prenthesis is stndrd devition. N minerliztion estimted from 0 kg N h -1 control plots. 114

134 Tble 4.3. Averge grin yield components nd wter dt by performnce clss cross ll dt points. Component Performnce Clss Number of Points (n) Men (std dev) Grin Yield, kg h (1473) 6208 (1480) 4697 (993) 5563 (1630) 3966 (726) Spikes m (108) 424 (108) 390 (88) 452 (96) 437 (91) Kernel mss, mg 28.2 (5.70) 26.3 (4.22) 28.3 (4.65) 29.3 (4.00) 30.3 (3.66) Kernels spike (11.3) 34.6 (13.4) 35.0 (14.1) 38.6 (13.1) 31.5 (8.4) Tillers per plnt 3.0 (1.4) 2.6 (1.6) 2.6 (1.3) 3.4 (1.5) 3.3 (1.4) Test Weight, kg hl (2.7) 78.1 (1.8) 75.3 (2.3) 74.6 (4.1) 73.2 (2.9) Hrvest Index 0.46 (0.06) 0.49 (0.04) 0.45 (0.04) 0.40 (0.06) 0.37 (0.04) Totl Biomss, kg h (3153) (3121) (2192) (2913) (2162) TMCWU, cm 31.8 (6.0) 31.8 (5.9) 26.3 (7.2) 29.5 (5.9) 28.2 (6.4) WUE, kg (h*cm) (50) 198 (46) 192 (69) 192 (60) 149 (49) Tv, cm 28.1 (7.5) 30.9 (4.7) 26.8 (8.1) 24.0 (8.5) 19.5 (5.4) TIN, kg h (63.7) (66.9) (45.1) (58.9) (41.0) Hrvest Index: Gw/Totl biomss; TMCWU: Consumptive Wter Use Tillering to Mturity, cm; WUE: Wter Use Efficiency, kg (h*cm) -1 ; Tv: Avil. Wter t Tillering, cm; TIN: Inorgnic soil N t tillering, kg h

135 Tble 4.4. Cross Vlidtion Results for Discriminnt Anlysis using Tretments (Lndscpe, N Rte, nd Seeding Rte), Grin Yield, Grin Protein Concentrtion, Ng/Nt nd Ng/Nf s best predictors. Priors re 0.2 for ech performnce clss. Number of Observtions nd Percent Clssified into Performnce Clss From Clss Totl Totl Totl Error Count ws 27% with the following by Performnce Clss error counts: Clss 1-28%; Clss 2-26%; Clss 3-22%; Clss 4-45%; nd Clss 5-16%. 116

136 Figure 4.1. Dichotomous key to clssifiction of soft white winter whet performnce bsed on N use efficiency criteri of N utiliztion efficiency (Gw/Nt) nd N uptke efficiency (Nt/Ns). Note NUE (Gw/Ns) is product of Gw/Nt nd Nt/Ns. 117

137 Grin Yield, kg h Nitrogen in Grin (Ng), kg h b Ns vs Ng - 1 Ns vs Ng - 2 Ns vs Ng - 3 Ns vs Ng - 4 Ns vs Ng Grin protein, g kg -1 Clss1 Clss 2 Clss 3 Clss 4 Clss 5 N Supply (Ns), kg h c d GW1-1 GW1-2 GW1-3 GW1-4 GW1-5 Grin Yield, kg h Grin Yield, kg h Ng vs GW1-1 Ng vs GW1-2 Ng vs GW1-3 Ng vs GW1-4 Ng vs GW Nitrogen Supply (Ns), kg h -1 Nitrogen in Grin (Ng), kg h -1 Fig Grin yield, grin protein nd N supply reltionships for ll lndscpe by N rte by seed rte plot dt between 2010 nd 2012 by Performnce Clssifiction. 118

138 Nitrogen Use Efficiency (Gw/Ns) Nitrogen Utiliztion Efficicney (Gw/Nt) b y = x r 2 = GPr vs GwNt - 1 GPr vs GwNt - 2 GPr vs GwNt - 3 GPr vs GwNt - 4 GPr vs GwNt - 5 Plot 1 Regr W1-1 W1-2 W1-3 W1-4 W1-5 Grin Yield, kg h c Grin Protein Conc., g kg Clss 1 Clss 2 Clss 3 Clss 4 Clss 5 Nitrogen in Grin (Ng), kg h d Grin Protein Conc., g kg -1 y = x r 2 = Nt vs Ng - 1 Nt vs Ng - 2 Nt vs Ng - 3 Nt vs Ng - 4 Nt vs Ng - 5 Plot 1 Regr Aboveground Plnt N (Nt), kg h -1 Aboveground Plnt N (Nt), kg h -1 Fig 4.3. The reltionship between N use efficiency, N utiliztion efficiency, grin yield, nd grin protein concentrtion by Performnce Clssifiction for ll lndscpe by N rte by seed rte plot dt between 2010 nd

139 Nitrogen Uptke Efficiency (Nt/Ns) Aboveground Plnt N (Nt), kg h b Ns vs Nt - 1 Ns vs Nt - 2 Ns vs Nt - 3 Ns vs Nt - 4 Ns vs Nt - 5 s Nt - 1 s Nt - 2 s Nt - 3 s Nt - 4 s Nt - 5 Aboveground Plnt N (Nt), kg h c Grin Protein Conc., g kg Avilble N (Nv), kg h -1 Avilble N (Nv), kg h -1 Clss 1 Clss 2 Clss 3 Clss 4 Clss d Nitrogen Supply (Ns), kg h Nitrogen Supply (Ns), kg h -1 Ns vs Nv - 1 Ns vs Nv - 2 Ns vs Nv - 3 Ns vs Nv - 4 Ns vs Nv - 5 Fig 4.4. The grin yield nd grin protein reltionship to N uptke efficiency for ll lndscpe by N rte by seed rte plot dt from 2010 to 2012 by Performnce Clss. 120

140 b NBS FS SBS SU Frequency c Performnce Clss 250 d Performnce Clss Frequency Performnce Clss Performnce Clss 0 kg N h to 48 kg N h to 80 kg N h kg N h kg N h kg N h seeds m seeds m to 165 seeds m seeds m to 250 seeds m seeds m-2-2 Figure 4.5. Frequency of performnce clsses by site yer (), lndscpe (b), N rte (c) nd seed rte (d). Nitrogen rtes for 2010: 0, 48, 75, 103 kg h -1 nd for 2011 nd 2012: 0, 40, 80, 120, 160 kg h -1. Seeding rtes for 2010: 98, 165, 230 plnts m -2 nd for 2011 nd 2012: 80, 165, 240, 335 plnts m

141 CHAPTER 5 COMPARISON OF QUANTIFICATION APPROACHES IN OFFSET PROTOCOLS FOR AGRICULTURAL NITROGEN MANAGAMEN: RELEVANCE TO PACIFIC NORTHWEST DRYLAND AGRICULTURE EXECUTIVE SUMMARY Nitrous oxide (N2O) emission reductions from griculturl N mngement hve the potentil to offset rising levels of tmospheric GHG s by 0.2 to 0.6 t CO2e h -1 yr -1 (Egle et l., 2012). Agriculturl N mngement ws the lrgest source of U.S. N2O emission (69%) in 2011 (USEPA, 2013). Emission reductions hs therefore been considered n importnt short-term mitigtion strtegy for the griculturl sector (Egle et l., 2012). In ddition, griculturl N2O emissions re the lrgest source of nthropogenic GHG from griculturl sources (USEPA, 2013). Under current greenhouse gs offset progrms, emission offset credits generted by griculturl nitrogen mngement ctivities re bsed on reducing the nnul N fertilizer ppliction rte for given crop without reducing yield. Nitrogen rte reductions cn be chieved through brod rnge of N fertilizer mngement strtegies including modifictions in fertilizer rte, type, plcement, nd timing; use of time-relese fertilizers; nd use of nitrifiction inhibitors (Egle et., 2012). Greenhouse gs emission reductions from reducing N rte re promising from crbon credit stnd point becuse they re not reversible. A rod test of griculturl N mngement protocols ws performed following the pproch of Lee et l. (2013) to provide frmework for ddressing the role of N bsed GHG offset progrms in the drylnd Pcific Northwest (PNW) whet-bsed cropping systems. There re four voluntry greenhouse gs reduction progrms with griculturl N mngement protocols in North Americ. This includes the Americn Crbon Registry (ACR), 122

142 Verified Crbon Stndrd (VCS), Climte Action Reserve (CAR), nd Albert Offset Credit System (Albert). Three N2O emission quntifiction protocols re currently pplicble to the PNW within two of these progrms: two within the ACR nd one under the VCS progrm. One of the ACR protocols specifies the use of the Denitrifiction Decomposition Model (DNDC) for clculting bseline nd project emissions. While eligible for projects in the PNW, the protocol ws not included in the rod test due to the time nd expertise required to use the DNDC model. The CAR nd Albert protocols re not pplicble becuse the CAR protocol is specific to corn nd the Albert protocol is specific to the Cndin province of Albert. Therefore, the rod test ws performed using the ACR2 nd VCS protocols s they were found to be the only pplicble to the PNW nd pproprite for this nlysis. Three smple projects were developed for the rod test to represent fesible N fertilizer rte reduction ctivities under PNW drylnd whet bsed cropping systems. Smple projects 1 nd 2 include N rte reductions estimted to result from switching from hrd red whet mrket clss to soft white mrket clss, resulting in N rte reductions of 85 nd 113 kg N h -1, respectively. Smple project 3 explored doption of site-specific N mngement of whet nd ws predicted to result in field verge N rte decrese of 33 kg N h -1 compred to uniform N mngement. The impct of direct emission fctors (1% versus 0.2%) on the mount of offsets generted ws lso evluted. The specific im ws to quntify emission reductions under relevnt protocols using the smple projects in order to evlute the relevnce of existing methodologies nd reltive importnce of N2O offsets for PNW cropping systems. 123

143 The ACR2 nd VCS protocols hve identicl bseline nd project emission quntifiction methodologies. This resulted in the sme bseline, project, nd emission reduction vlues under the two protocols. An emission reduction of 0.55 nd 0.73 Mg CO2e h -1 yr -1 ws obtined under smple project 1 nd 2, respectively. Vrible rte N ppliction (project 3) resulted in the lowest emissions reduction (0.21 Mg CO2e h -1 yr -1 ) but my be pplicble to greter mount of crege nnully compred to smple projects 1 nd 2. Across the rnge of C prices considered ($5, 10, nd 50 per metric ton of crbon dioxide equivlent), it ws concluded tht the incentive pyment for N2O emission reductions ws unlikely to impct on-frm N mngement decisions ($0.4 to 36.5 h -1 ). However, including the fertilizer cost sving incresed the incentive pyment considerbly. Across ll smple projects, combining the fertilizer cost sving ($29 to 97 h -1 ) with the crbon pyment resulted in less disprity with the potentil return from growing hrd red whet clsses over growing soft white whet clsses. The use of N rte under these protocols is simplifiction tht is useful but it my not be the most effective policy tool for PNW drylnd whet cropping systems. Development of PNW focused protocol should utilize n groecologicl zone pproch involving the development of regionl emission fctors nd prioritizing project ctivities for chieving the gretest GHG emission reductions. INTRODUCTION Greenhouse Gs Emissions nd Offsets There is growing concern over rising tmospheric concentrtions of nitrous oxide (N2O), greenhouse gs 310 times more potent thn crbon dioxide (CO2) (Robertson nd Vitousek, 124

144 2009; USEPA, 2013). Greenhouse gs concerns re coupled with negtive environmentl consequences ssocited with ccelerted rtes of rective N entering nd cycling through ecosystems (Vitousek et l., 1997; Robertson nd Vitousek, 2009). The griculturl sector is the lrgest contributor to rising N2O emissions in the U.S. (USEPA, 2013). Of the mjor U.S. N2O emission sources, 69% of emissions were from griculturl soil mngement (Figure 5.1b) (USEPA, 2013). Within the griculturl sector, N2O emissions from griculturl soil mngement contributed of the Tg CO2e of N2O-N emitted nd represents the lrgest source of nthropogenic greenhouse gs emissions from the griculture (USEPA, 2013). Incresed nitrous oxide emission rtes result from ppliction of synthetic N fertilizer, mnure dditions, nd dringe nd cultivtion of orgnic soils (USEPA, 2013). However, n incresing world popultion will demnd greter griculturl productivity from cropping systems tht re relint on synthetic N fertilizers to chieve high yields. This hs plced considerble pressure on griculture to reduce hydrologic or gseous losses of N without compromising yield (Robertson nd Vitousek, 2009). Agriculturl N mngement prctices tht reduce N fertilizer ppliction rtes without reducing crop yields hve the potentil to reduce griculturl N2O emissions, generte greenhouse gs offsets, nd enhnce overll environmentl qulity. Greenhouse gs offsets re emission reductions chieved t sources outside of cpped sector tht result in GHG offset credits. Offset progrms provide mechnism where covered entities cn offset their emissions by purchsing emission reduction credits. Offset protocol methodologies hve been developed to ensure tht greenhouse gs emission reductions re ctully chieved (rel nd verifible) nd beyond wht would hve occurred without the 125

145 incentive of the GHG offset progrm (dditionl) (Broekhoff nd Zyl, 2008). The protocol methodology for quntifying emission reductions re the stndrd for ccurte ccounting of emission reductions nd offset credits generted by project ctivities. Offset quntifiction protocols re therefore criticl for estblishing credibility in emission reductions nd offset mrkets. The focus of this report is on the methodologies for quntifying GHG offset credits generted under current griculturl nitrogen mngement offset progrms. The quntifiction will be pplied to smple projects developed tht re relevnt to drylnd (i.e., rin-fed) whet cropping systems of the Pcific Northwest (PNW). This ws used to evlute the relevnce of current offset progrms nd quntifiction protocol methodologies to PNW groecosystems. Emission offset credits generted by griculturl nitrogen mngement ctivities re bsed on reducing the overll N fertilizer ppliction rte nnully pplied to crop. However, N fertilizer rte reductions must not result in substntil decrese in yield. Fertilizer N rte reductions hve been trgeted in offset progrms becuse the ddition of N increses the mount of vilble soil N for processes tht produce N2O in griculturl soils (i.e., nitrifiction nd denitrifiction) (IPCC, 2006 V4 Ch11). Overll, the quntifiction of N2O emissions from N fertilizer ddition re more developed for corn grown under Midwest US mngement prctices (Millr et l., 2012; VCS, 2013). A rod test of griculturl N mngement protocols ws performed following the pproch of Lee et l. (2013) to provide frmework for ddressing the role of N bsed GHG offset progrms for PNW drylnd griculture. Three smple projects were developed to represent fesible N fertilizer rte reduction ctivities tht could be ccomplished under PNW drylnd whet production. In ddition, the impct of direct emission 126

146 fctor used (i.e., Tier I versus Tier II or III) on the mgnitude of offsets generted ws evluted. The objective of this project ws to quntify emission reductions under existing protocols in order to evlute the relevnce of existing methodologies nd importnce of N2O offsets in guiding griculturl N mngement decisions for PNW whet bsed cropping systems. Generl Description of Pcific Northwest Drylnd Agriculture Drylnd spring nd winter whet re mjor crops of the PNW region tht includes Wshington, Oregon nd Idho. The whet growing region is lso referred to s the Northwest Whet nd Rnge Region nd covers pproximtely 21 million hectres (USDA, 2006). In these drylnd res climte is mjor fctor influencing the distribution of crops nd gronomic mngement systems (Ppendick, 1996). Low precipittion res receive less thn 375-mm of precipittion nnully nd re typiclly mnged using two yer winter whet - summer fllow rottion (Rsmussen et l., 1998; McCool nd Roe, 2005). Intermedite precipittion zones receive 375- to 450-mm of rinfll nnully (Rsmussen et l. 1998; McCool nd Roe, 2005) nd re plnted using two to five yer rottion usully consisting of winter whetspring brley or spring whet - summer fllow (Ppendick, 1996). Annul cropping is prcticed in res tht receive greter thn 450-mm of wter nnully (high precipittion zones) nd tend to be chrcterized by two to three yer rottion of winter whet, spring brley, spring whet, nd/or spring legume (Ppendick, 1996; Rsmussen et l., 1998; McCool nd Roe, 2005). Offset Credits from Agriculturl Nitrogen Mngement 127

147 There re four voluntry greenhouse gs reduction progrms with griculturl N mngement protocols in North Americ. This includes the Americn Crbon Registry (ACR), Verified Crbon Stndrd (VCS), Climte Action Reserve (CAR), nd Albert Offset Credit System (Albert). The ACR nd VCS progrms hve interntionl pplicbility. The CAR progrm is pplicble to project loctions within the US nd the Albert progrm is pplicble in the Cndin province of Albert. All the progrms listed in Tble 5.1 re ssocited with n offset registry system where verified emission reductions from project ctivities cn be serilized nd trcked in trnsprent mnner. Agriculturl N mngement protocols (Tble 5.2) re developed within these progrms s pproved methodologies for quntifying N2O emission reductions resulting from doption of pproved mngement prctices. Bsed on the regionl scope, only three of the five quntifiction protocols for griculturl nitrous oxide emissions cn be pplied to whet bsed cropping systems of the PNW (Tble 5.2). For the PNW this would include the two ACR nd the VCS quntifiction protocols. While sites throughout the US re eligible under the CAR progrm, the only griculturl N mngement protocol currently pproved by CAR is specific to corn crops grown in the North Centrl Region of the U.S. While not currently pplicble to the PNW, we included the Albert nd CAR protocols in our review becuse their generl fetures nd quntifiction pproches my help inform the development of protocol specific to the PNW. New N mngement protocols cn be submitted to these progrms to improve pplicbility to regionl or cropping system specific conditions regulting N2O emissions. New protocols must be reviewed nd pproved before they cn be used under progrm (e.g., Midwest corn). 128

148 An offset project includes doption of n pproved mngement prctice(s) tht hs been identified within n offset progrms quntifiction protocol (e.g., Tbles 5.1, 5.2 nd 5.3) to reduce GHG emissions. No GHG offset projects for griculturl N mngement projects hd been registered under ACR, CAR, or VCS t the time of writing this report (Online registries ccessed 6/25/2013). However, VCS hd the lrgest number of other greenhouse gs offset projects registered (1039 projects; ~128 million metric tons CO2e offsets issued) followed by CAR (203 projects; ~35 million metric tons CO2e offsets issued), Albert (142 projects, ~48 million metric tons CO2e offsets issued), nd ACR (15 projects; ~38 million metric tons CO2e offsets issued) (Appendix 10.1). AGRICULTURAL N MANAGEMENT TO REDUCE N2O EMISSIONS For these protocols fertilizer N rte is used s n integrtor of severl mngement prctices tht cn be dopted lone or simultneously to reduce N2O emissions. This might include dopting crop rottions with n N cpturing component, improving prediction of N requirement, nd employing the 4-R frmework of right plce, right time, right source, nd right rte (Robertson nd Vitousek, 2009; Roberts, 2006). Offset protocols for griculturl N mngement encourge prctices tht better predict crop N demnd nd increse nitrogen use efficiency (Robertson nd Vitousek, 2009; Millr et l., 2012). The principles of precision griculture re often employed to chieve reduced N fertiliztion rtes while lso meeting crop N demnd. Precision griculture techniques mke use of fertilizer N rte, timing, plcement, nd formultion to mtch N supply with crop demnd (Robertson nd Vitousek, 2009). An overll N rte decrese cn often, but not lwys, be relized by pplying one or more of these 129

149 principles (Huggins, 2010). In evluting the potentil to generte GHG offset credits from griculturl N mngement for prticulr region, it is importnt to consider the trdeoffs nd wht level or type of incentive is needed to influence N mngement decisions. Adoption of precision griculture techniques within the PNW generlly lcks sufficient decision support (Pn et l., 1997; Huggins, 2010) nd monetry incentives. Nitrogen fertilizer rte reductions will likely be seen s economiclly risky nd require some level of monetry incentive to offset the risk of under pplying N (Robertson nd Vitousek, 2009; Huggins, 2010). Eligibility Requirements Quntifiction protocols include generl project eligibility conditions such s project loctions, project strt dtes, nd dditionlity requirements (Tble 5.3). The project strt dte indictes the erliest dte tht project ctivities cn be credited for offsets generted. The differences in eligible project strt dtes my hve implictions for driving innovtion nd doption of GHG reduction techniques or technologies but does not pper to impct offset quntifiction. As first evlution of quntifiction methodologies, protocols whose eligible project loctions included the PNW (i.e., Wshington, Idho, Oregon) were considered currently pplicble to PNW whet bsed cropping systems. The ACR nd VCS protocols re currently the only three tht re pplicble to the PNW bsed on eligible project loction. Projects re ccepted on lnd worldwide under the ACR1 (ACR, 2010) nd ACR2 (Millr et l., 2012) protocols. The VCS protocol (VCS, 2013) is pplicble for offset projects occurring within the US. 130

150 Project strt dtes, eligible crops, nd regultory surplus requirements determine the eligibility of projects, but once stisfied do not fctor into the quntifiction of offsets generted (Tble 5.3). Fertilized griculturl crops tht require externl N inputs to chieve high production of food, fiber, or fodder re ccepted under ll the protocols except CAR (corn only). Regultory surplus is one of the dditionlity tests nd generlly requires tht project ctivities be in ddition to wht is required under current lws nd regultions. All of the protocols require project ctivities within the US to be surplus to regultion. There re some differences in regultory surplus requirements mong protocols but these differences do not impct the quntifiction of offsets generted by project ctivities. Eligible N Sources Sources of N input into cropping system during ny given crop yer cn include mnure, synthetic fertilizer, crop residue N, soil orgnic mtter minerliztion nd biologicl N fixtion. There re some differences mong the protocols s to wht N fertilizer sources re credited under the offset quntifiction methodology (Tble 5.3). The ACR, VCS, nd Albert protocols issue emission offset credits for N rte reductions from both inorgnic nd orgnic N sources. Under CAR, the N rte reduction cn include both synthetic nd orgnic N sources but only synthetic N fertilizer sources re credited for emission reductions. The Albert protocol lso includes the quntifiction of N inputs from crop residue decomposition (Soil Crop Dynmics). Approved N Mngement Activities 131

151 Nitrogen rte is fvorble metric for offset progrm quntifiction methodologies becuse N rte reductions reltive to the bseline re reltively esy to monitor nd verify (IPCC, 2006 V4 Ch11). The ACR1 protocol ccepts brod rnge of fertilizer mngement ctivities to reduce N rte (i.e., chnge in fertilizer rte, type, plcement, timing, use of timerelese fertilizers, nd use of nitrifiction inhibitors). The ACR2 nd VCS protocols require dherence to regionlly dpted N fertilizer best mngement prctices (BMP s). This includes N fertilizer source, timing of N ppliction, nd method of N fertilizer ppliction. Under ACR2 nd VCS, project developers re referred to stte specific resources for detiled N fertilizer BMP s (e.g., USDA-NRCS). The Albert quntifiction protocol, distinct from the other protocols, requires project prticipnts to dopt the Consistent 4R Nitrogen Stewrdship Pln which is n integrted set of mngement prctices. There re three performnce levels within the Consistent 4R Nitrogen Stewrdship Pln: bsic, intermedite, nd dvnced. A greter mount of field vribility must be ddressed nd more complex BMP s dopted s prticipnt moves to the intermedite nd dvnced levels of the pln. The CAR protocol does not specify eligible prctices but requires tht totl nnul N pplied must decrese below bseline. Overll, the prctices required to chieve the performnce levels in the ACR, VCS, Albert, nd CAR protocols lign with the principles of precision griculture. Mngement Options to Reduce N Fertilizer Rtes for PNW Whet Mnging N in cropping systems involves considertion of the totl N supply needed for not only supporting crop growth but lso chieving grin yield nd qulity (Huggins nd Pn, 2003). There re five different mrket clsses of whet grown in the Plouse region of the 132

152 PNW: soft white, hrd red winter, hrd red spring, hrd white nd durum. The clss designtions relte to whet chrcteristics importnt to the end use qulity of the grin (i.e., mrket clss). Grin protein content is qulity chrcteristic of whet clss tht is importnt to N fertilizer mngement decisions. The desired protein content for soft white clsses of whet is 9% protein (Koenig, 2005). The protein gol for hrd red winter whet is 11.5% nd hrd red spring whet 14% (Koenig, 2005). The different protein requirements of the mrket clsses result in different mounts of N nutrition needed to chieve the protein s well s yield gol (Koenig, 2005). The lower protein requirement of soft white whet results in lower N fertilizer rte requirements compred to hrd red clsses (Tble 5.5). This is prticulrly true for the spring whet mrket clsses (9% versus 14% for soft white nd hrd red, respectively). Description of Smple Projects For this rod test we utilized frm records nd N mngement prctices from the Cook Agronomy Frm (CAF), ner Pullmn, WA to develop the smple projects nd quntify N2O emission reductions under existing griculturl N mngement protocols. The CAF is reserch frm tht lies within the high precipittion zone of the PNW drylnd frming region. The frm is under nnul cropping nd hs been direct-seeded since The soil, gronomic, nd field conditions re representtive of typicl estern Wshington Plouse lndscpe. Field specific crop nd N mngement dt from the 37 hectre (90 cre) cropping system reserch field ws used for the rod test (Huggins, 2010b). The frm receives n verge of 550-mm of precipittion nd is under three yer cerel rottion (minly whet, brley, nd legume crops). A three yer rottion of winter whet spring whet spring legume ws used cross 133

153 ll of the smple projects nd is typicl of the region. The historic rottion determines the number of pre-project crop yers used to quntify bseline N2O emissions. Project offsets re quntified on crop event bsis so tht offset credits re only generted for ech yer the credited crop is grown nd mnged under the project conditions. For exmple, credits from chnge in N rte pplied to winter whet crop will only be generted in the yers winter whet is grown during the crediting period. In generl the rottion is not expected to chnge s this might crete lekge. Annul N fertilizer dditions re function of the current crop N demnd, N credits from soil-residue N cycling, nd soil inorgnic nitrogen content in the soil before plnting (Koenig, 2005). Hrd red winter nd hrd red spring whet clsses (s described bove) were grown in the rottion during the first 10 yers of crop production t the CAF ( ). For the field specific dt, the verge yield ws clculted from the nine yers of hrd red spring nd winter whet dt from CAF nd the verge N rte from the rnge in fertilizer rtes for the sme yers. Hrd red whet clsses require more N thn soft white whet clsses in order to chieve desired grin protein concentrtions. The smple projects were designed to represent griculturl N prctices for chieving both high yield nd protein concentrtion under drylnd conditions in southestern Wshington. However, it is recognized tht these smple project ctivities my not represent the entire rnge if project circumstnces tht rise in prctice. For exmple, mny frmers my not pply the mount of N needed to obtin protein gols due to the high cost of N fertilizer. To improve the generl pplicbility of this project, the N2O emission results re reported on lnd re bsis (i.e., per hectre nd cre bsis). 134

154 Smple Projects 1 nd 2: Switch from Hrd Red to Soft White Whet Clss (Chnge in N Rte) Soft white whet clsses re the dominnt clss grown in Wshington Stte (Appendix Tble A-13). The higher price for hrd red whet clsses mke them more ttrctive thn soft white clsses. However, mny drylnd frmers in southestern WA nd northern ID hve indicted tht regulrly chieving the higher protein level of the hrd red mrket clsses is problemtic. Grin protein below the optimum for the hrd red clsses cn result in price discount. It is therefore fesible tht frmers would be willing to switch from hrd red to soft white whet clsses given: (1) the economic risk of discount for low protein; (2) the incresed N fertilizer input costs; nd (3) gronomic nd environmentl risks ssocited with greter N fertilizer use. Smple projects 1 nd 2 include N rte reductions tht could be chieved by chnging from hrd red whet mrket clss to soft white mrket clss. Smple project 1 involves switch from hrd red winter whet to soft white winter whet resulting in n N rte reduction of 85 kg N h -1 (75 lbs c -1 ). An N rte reduction of 113 kg N h -1 (100 lbs N c -1 ) ws chieved under smple project 2 for chnge from hrd red spring whet to soft white spring whet. Smple Project 3: Switch from Uniform to Vrible N Rte Appliction (Chnge in N Plcement) Currently, N fertilizer rte recommendtions for whet re bsed on n expected yield gol nd unit N requirement (UNR). The unit N requirement is the mount of nitrogen needed to produce one unit of grin (i.e., bushel). The UNR is generlly determined for crop, vriety, or in this cse whet clss cross given region (i.e., regionl fertilizer guides). Yield gol nd N 135

155 requirement re ssumed uniform cross given field nd re used to clculte uniform N ppliction rte. However, vribility in whet yield nd N requirement hs been observed cross griculturl fields within the Plouse region of the PNW (Mull et l., 1992; Fiez et l., 1994 nd b; Huggins, 2010). Fiez et l. (1994) reported winter whet grin yield to vry by up to 63% nd the unit N requirement up to 70% (southestern, WA). This indictes tht vrible rte N fertilizer ppliction hs the potentil to reduce overll N rte without decresing yield. For smple project three it ws ssumed tht site specific N mngement of soft white winter whet could, on verge, result in 33 kg N h -1 (30 lbs c -1 ) decrese in N fertilizer rte compred to uniform N mngement without decresing yield (Tble 5.5). This ws bsed on the work of Fiez et l. (1994) where vrible rte ws estimted to result in field verge N rte of 65 nd 81 kg h -1 (58 nd 73 lb N c -1, respectively) compred to the uniform rte of 106 kg h -1 (95 lbs N c -1 ). The men N rte reduction under smple project three (33 kg N h -1 ) ws considered relistic N rte decrese tht could be chieved by vrible rte N mngement nd lso likely cceptble to frmers. Impct of Emission Fctor for Direct N2O Emissions The Intergovernmentl Pnel on Climte Chnge (IPCC) methodology for estimting N2O emissions recognizes tht the Tier I defult emission fctor of 1% (i.e., 1% of N fertilizer pplied is lost s direct N2O emissions from the field) my be good for globl inventories but not for quntifying regionl N2O emissions (IPCC, 2006, V4 Ch11). There is some regionl dt to suggest tht the direct emission fctor for PNW cropping systems my be much lower thn the 1% emission fctor used under IPCC Tier I methodology. Cochrn et l. (1981) reported tht 136

156 N2O emissions were less thn 0.1% of the N pplied in whet-fllow system locted t Pullmn, WA. Their results lso showed tht N2O emissions were not liner function of N rte s is ssumed when using the IPCC Tier I emission fctor. The N2O emission rte ws shown to be well below the 1% IPCC Tier I direct emission fctor for irrigted croplnd conditions in Pterson, WA receiving N fertilizer dditions (Collins et l., 2010). Collins et l. (2010) reported N losses s N2O emissions ccounted for 0.18% of N pplied in pottoes (Solnum tuberosum L) nd 0.25 to 0.30% in corn (Ze mys L). Under smple project 4, Tier II pproch using direct emission fctor of 0.2% for the PNW ws pplied to the smple projects. QUANTIFYING EMISSION REDUCTIONS Greenhouse gs emissions re expressed s crbon dioxide equivlents (CO2e) nd reported in meggrm increments (Mg CO2e). A meggrm (Mg) is equivlent to metric ton (t). Crbon dioxide equivlents re globl wrming potentil weighting tht is bsed on rditive forcing over 100-yer time scle nd resulting from the relese of 1 kg of substnce s compred to 1 kg of CO2 (IPCC, 2006, V4 Ch11). Under ll of the protocols reviewed, globl wrming potentil of 310 ws used for N2O emission conversion to CO2e. This mens tht N2O is 310 times more potent of GHG thn CO2 under ll protocols. The generl eqution for clculting the N2O emission reduction from project ctivities is: Emissions Reduction, MtCO2e yr -1 = Bseline Emissions (BMtCO2e yr -1 ) Project Emissions (PMtCO2e yr -1 ) Sources nd Sinks Included in Emission Quntifiction The ssessment boundry is used to identify the GHG sources nd sinks to be included in the quntifiction of bseline nd project emissions. The ssessment boundry does not 137

157 necessrily represent physicl boundry. In the voluntry mrket, the sources nd sinks included in the quntifiction boundry is protocol specific. The sources nd sinks encompss the included or excluded direct nd indirect emissions ssocited with bseline nd project N mngement (Tble 5.4). Direct emissions re the emissions of N2O from N fertilizer ddition to the project lnds for enhncing crop productivity. The indirect emissions re the N2O emissions tht occur beyond the project site but re the result of N fertilizer pplied t the project field site. Indirect N2O emissions result from the re-deposition of voltilized mmoni, leching of N from the soil, nd N runoff to surfce wters (IPCC, 2006 V4 Ch11). The boundry my lso include combustion emission sources nd sinks from fertilizer mnufcture, distribution, or N ppliction to the field. There re some differences mong the protocols s to which emission sources re included in clculting emission reductions from project ctivities (Tble 5.4). Most notbly re the inclusion of fossil fuel emissions for ACR1, Albert, nd CAR s well s the inclusion of CO 2 nd N2O emissions from soil crop dynmics under the Albert protocol. The ACR1 protocol includes CO2, CH4, nd N2O from fossil fuel combustion on site while the Albert includes CO2 nd N2O from on-site fossil fuel combustion. The CAR protocol includes CO2 from fossil fuel combustion. The ACR2 nd VCS quntifiction methodologies do not include ny fossil fuel combustion emissions. The ACR1 methodology lso includes CO2 emissions from fertilizer production but not fertilizer distribution. Fossil fuel emission sources could be importnt under project ctivities if N fertilizer mngement chnges result in incresed fossil fuel consumption (e.g., more trips cross the field for split ppliction of N). Another difference is tht the ACR1 138

158 protocol does not include the indirect N2O emissions from runoff. The other protocols include indirect N2O from N runoff s well s N2O emissions from re-deposition of voltilized N nd N leching. The ACR2 nd VCS protocols ccount for the sme sources nd sinks under bseline nd project N2O emission quntifiction. Some emission sources or sinks my be excluded nd justified s incresing the conservtiveness of the project. For exmple, ACR2 nd VCS exclude emission reductions from fertilizer production nd distribution s mens to increse the conservtiveness of the emission reduction estimte. Crbon sequestrtion is not included in ACR1, ACR2, VCS, Albert, or CAR protocols becuse N fertilizer rte reductions re not expected to impct soil C stocks. The exclusion is considered to increse the conservtiveness of the offset quntifiction (Millr et l., 2012; ACR, 2010). Additionl to Business s Usul Additionlity for these protocols is bsed on performnce stndrd of reducing the N fertilizer ppliction rte on project lnds, nd subsequently N2O emissions, below tht of the bseline. Bseline N2O emissions represent the emissions tht would hve occurred bsent the offset mrket incentive. It is importnt tht protocol quntifiction methodologies ssure offsets generted by project re rel nd not result of inccurte quntifiction methodologies. Overll the protocols differ slightly in the number of yers of historicl crop dt used to clculte the bseline N fertilizer rte (Tble 5.5). This could result in different bseline N2O emissions which could impct offsets generted by project. The ACR2 nd VCS use the sme number of yers nd depend on the crop rottion. The number of crop yers 139

159 rnges from two to five yers. The ACR1 protocols specifies five nd Albert three previous crop yers. Under CAR, t lest 3 nd up to five previous crop yers re used to clculte the bseline N fertilizer rte nd subsequent emissions. Another difference is in the pproved dt sources for clculting the bseline emissions. Field specific dt is required under the Albert nd CAR quntifiction methodologies. The ACR2 nd VCS protocols provide the option of using field specific dt or county level dt (yield-gol bsed pproch with regionl fertilizer guides) to determine the bseline N rte contributing to bseline N2O emissions. Lekge Lekge provisions in griculturl N mngement protocols specify tht N rte reductions must not result in decrese in yield. Though not ddressed in current protocols, it should lso be noted tht frm economics would lso require ny N rte reductions to not come t the expense of yield qulity (e.g., protein concentrtion specifictions for the whet mrket clss). Mintined yield with less N is believed to be possible becuse typicl yield-gol bsed N fertilizer recommendtions tend to overestimte N requirements (Millr et l., 2012). This could be especilly true for winter whet crops in the PNW becuse it is difficult to ccurtely estimte yield gol t the time of plnting nd fertiliztion (i.e., growing seson conditions cnnot be predicted). For drylnd winter whet, mjority of N fertilizer is pplied in the fll when N demnd is the lowest. Yield my lso be mintined with less N in situtions where N is pplied in excess of the N requirement to minimize economic risk if growing conditions re exceptionl (i.e., insurnce ppliction). Insurnce pplictions of N s mens to mnge the economic risk of under pplying N should not be dismissed. Especilly 140

160 considering tht decision support nd other incentives re generlly lcking for mnging the site-specific N requirement. An dditionl monetry incentive my be needed to offset insurnce pplictions. There is concern tht shifting from hrd red to soft white whet mrket clsses will result in the production of hrd red whet elsewhere in the region. This would crete lekge tht negtes N2O emission reductions from project ctivities by merely chnging the site of N2O production to non-project lnds. In contrst, corn crops do not tend to be fertilized t different rtes mong the end use mrket (i.e., hybrids). The difference between corn nd whet bsed cropping systems underscores the need for regionlized or groecosystem specific protocols. Adoption of vrible rte N ppliction under smple project three is not expected to result in lekge. Defult Vlues for Clculting Direct nd Indirect N2O Emissions Currently, the ACR2 nd VCS protocols use Tier II emission fctor for direct N2O emissions from N fertilizer dditions to corn crops (Millr et l., 2010) with the remining griculturl crops defulting to the IPCC Tier I emission fctor (Tble 5.6). The ACR1, ACR2, nd VCS protocols use the IPCC Tier I defult fctors in quntifying indirect N2O emissions. Under the IPCC methodology, the direct nd indirect emissions from ppliction of N fertilizer to griculturl soils re clculted ccording to three tier pproch s outlined in the IPCC Good Prctice Guidnce for Lnd Use, Lnd-Use Chnge nd Forestry (GPG-LULUCF) (IPCC, 2006, V4 Ch11). As quntifiction methods move from Tier I to Tier III emission fctor pproch, the uncertinty in the emission quntifiction is reduced (i.e., improved ccurcy). However, 141

161 determintion of emission fctors under the Tier II nd Tier III pproches re more complex nd expensive to mesure (Brcmort, 2011). The direct emission fctor bsed on N fertiliztion rte under the IPCC Tier I pproch (1% of N fertilizer pplied to soil emitted s N2O-N) does not ccount for regionl differences in environmentl conditions or mngement prctices (IPCC, 2006 V4 CH11). For the Tier II pproch, the project emission fctor(s) re bsed on specific conditions such s N source, crop type, mngement, climte, or soil conditions. Under Tier III modeling or mesurement pproch is tken to determine emissions (IPCC, 2006 V4 CH11). N2O Emissions for Smple Projects Using Applicble Protocols The overll im of this review nd quntifiction ws to evlute if current protocols cn or should be pplied to PNW drylnd griculturl systems. Quntifiction will llow for ssessment of N2O offsets s n incentive for mitigting GHG emissions nd reducing the mount of rective N entering the environment. Emission reductions were quntified for the smple projects using the protocols tht were currently pplicble to PNW whet cropping systems. The ACR1, ACR2 nd VCS protocols were currently pplicble to PNW drylnd whet cropping systems. The ACR1 protocol specifies the use of the Denitrifiction Decomposition Model (DNDC) for clculting bseline nd project emissions. The ACR1 quntifiction methodology, while eligible for projects in the PNW, ws not included in the rod test becuse the time nd expertise required to use the DNDC model ws considered outside the scope of this project (ACR, 2010). The rod test ws completed using the ACR2 nd VCS protocols becuse they were found to be the most pplicble nd pproprite for the PNW. Emissions for Smple Projects 1 nd 2 by Protocol nd Bseline Approch 142

162 For ACR2 nd VCS, bseline N fertilizer rte cn be clculted using one of two pproches. One pproch relies on field specific N ppliction records from the project field for specified number of crop yers prior to the project (Tble 5.5). The other pproch utilizes county level dt to estimte N ppliction rtes for specified number of crop yers prior to the project. Bseline fertilizer N rtes clculted from county level dt require yield gol estimte clculted from county level yield records vilble from the USDA-Ntionl Agriculturl Sttistics Service (USDA-NASS) nd yield-gol bsed nitrogen recommendtions obtined from regionl fertilizer guides (e.g., Koenig, 2005). The number of yers to be considered in clculting the verge yield gol for the county level estimte of bseline emissions ws the two most recent yers since the project scenrios were developed ssuming three yer crop rottion s specified in the protocol quntifiction methodology (Tble 5.5). The two yers of county level yield dt for winter whet ws from 2007 nd 2010 nd for spring whet included 2008 nd 2011 yield dt (Clcultion in Appendix A-11). The impct of the bseline N2O emission quntifiction pproch ws included in this evlution to inform progrm or protocol development. The ACR2 nd VCS protocols hve identicl bseline nd project emission quntifiction methodologies (e.g., use the sme defult fctors for direct nd indirect emissions, Tble 5.6). For the project scenrios both protocols use two crop yers to clculte the bseline emissions since it is prt of three yer rottion (winter whet spring whet legume; Appendix Tble 11.1). This resulted in the sme bseline, project, nd emission reduction vlues under the two protocols (Figure 5.2). The pproch used in determining bseline N2O emissions ws found to 143

163 impct the quntity of bseline emissions nd hence emission reductions from the project ctivity. Using two yers of county level dt for yield gol bsed N fertilizer recommendtion rte, s specified in the protocol methodology, resulted in 0.16 nd 0.10 Mg CO2e h -1 yr -1 less emission reduction credits for smple project 1 nd 2, respectively, compred to field specific N dt. This resulted from more conservtive bseline N2O emission rte (1.07 Mg CO2e h -1 yr - 1 ) using county level dt compred to field specific N mngement records (1.23 Mg CO2e h -1 yr -1 ). The lower bseline emissions quntified from county level dt resulted in fewer offset credits generted for the smple projects s compred to the offsets generted under the field specific N ppliction pproch to quntifiction. Offsets Generted for Smple Projects 1, 2 nd 3 (Tier I Emission Fctor) An emission reduction of 0.55 nd 0.73 Mg CO2e h -1 yr -1 ws obtined under smple project 1 nd 2, respectively. Vrible rte N ppliction (smple project 3) resulted in the lest mount of emission offsets (0.21 Mg CO2e h -1 yr -1 ) compred to switching from hrd red to soft white whet mrket clss (Figure 5.3). This resulted from the higher N rte reduction under smple projects 1 nd 2 compred to smple project 3. Smple project 1 ctivities resulted in n N rte decrese of pproximtely 84 kg N h -1 (75 lbs N c -1 ) while smple project 2 resulted in n N rte decrese of 112 kg N h -1 (100 lbs N c -1 ). The difference in N rte reduction, nd subsequent emission offset, between smple projects 1 nd 2 results from the higher protein gol of hrd red spring whet (14%) compred to hrd red winter whet (11.5%) (Figure 5.3). Smple project 3 ws chrcterized by 33 kg N h -1 (30 lbs N c -1 ) reduction in N fertilizer ppliction from employing vrible s compred to uniform N rte ppliction (Figure 5.3). 144

164 Smple Project 4: Influence of Regionl Emission Fctors (Tier I versus Tier II) Current protocols do not hve emission fctors specific to PNW whet-bsed cropping systems. This mens tht IPCC defult fctors must be used to clculte emission reductions from smple project ctivities. IPCC methodology recognizes tht the 1% of nitrogen fertilizer rte emission fctor for direct N2O emissions my be good for globl inventories but not for quntifying regionl N2O emissions (IPCC, 2006, V4 Ch11). Some regionl dt shows tht the direct emission fctor for PNW cropping systems my be much lower thn the IPCC Tier I methodology defult. Cochrn et l. (1981) reported tht N2O emissions were less thn 0.1% of the N pplied in whet-fllow system in Pullmn, WA. Their results lso showed tht N2O emissions were not liner function of N rte s is ssumed using the IPCC Tier I emission fctor. The N2O emission rte hs lso been found to be well below the 1% IPCC Tier I direct emission fctor for irrigted N fertiliztion conditions in Pterson, WA (Collins et l., 2010). Collins et l. (2010) reported N2O emission losses, s percentge of N pplied, ccounted for 0.18% in pottoes (Solnum tuberosum L) nd 0.25 to 0.30% in corn (Ze mys L). Using Tier II pproch nd ssuming direct emission fctor of 0.2% of N fertiliztion rte for whet resulted in the genertion of offset credits tht were 2.5 times lower compred to the Tier I emission fctor (Figure 5.4). The Tier II emission reductions were 0.22, 0.29, nd 0.08 Mg CO2e h -1 yr -1 for smple projects 1, 2, nd 3, respectively. This is in comprison to the 0.55, 0.73, nd 0.21 MgCO2e h -1 yr -1 emission reductions generted using Tier I pproch for smple projects 1, 2 nd 3, respectively (Tble 5.7). This resulted in decrese of 0.33, 0.44, nd 0.13 MgCO2e h -1 yr -1 in offset credits generted under Tier II compred to Tier I 145

165 pproch for smple projects 1, 2, nd 3, respectively. It is importnt to note tht for this nlysis only the direct emissions chnged (Tble 5.7). The defult indirect emissions dt remined the sme for ech smple project. IS THIS ENOUGH TO IMPACT MANAGEMENT DECISIONS? Here we exmined the potentil revenues frmers could ern by prticipting in the crbon mrket. Tble 8 shows the potentil revenue tht could be generted per hectre from reducing N2O emissions through griculturl N mngement offset projects in the higher precipittion zone of the drylnd PNW. This nlysis is bsed on three offset price scenrios for ech unit of N2O emissions reduction (i.e., $5, $10, or $50 per Mg CO2e). Our estimtes consider only gross offset revenue nd not ny trnsction costs ssocited with offset project development. Smple project two hs the highest per hectre pyment incentive followed by smple project one nd then three. The offset credit incentive pyment lone does not pper to be enough to impct mngement decisions t offset prices of $5, $10, or $50 per MgCO2e ($0.8 to $7.3 h -1 ) bsed on the difference in whet prices for hrd red compred to soft white whet from 2008 to 2013 (Tble 5.10). The five yer Port of Portlnd price for HRWW (11.5% protein) rnged from $5.59 to $7.84 per bushel ( ). Soft white winter whet rnged from $4.91 to $8.34 per bushel. Hrd red spring whet (14% protein) rnged from $6.81 to $9.89 per bushel while SWSW rnged from $5 to $7 per bushel. Under Tier I pproch, the incentive becomes more ppeling t $50 per MgCO2e when the difference in returns over vrible costs for hrd red s compred to soft white whet clsses is considered in conjunction with cost 146

166 svings in fertilizer. However, if lower direct emission fctor is more ccurte (0.2% of N pplied) the offset credit incentive lone does not pper to be enough to impct griculturl N mngement decisions cross ll offset prices. The incentive is substntilly incresed when the cost svings on fertilizer for ll smple projects is included with the crbon pyment incentive (Tble 5.9). At verge nhydrous mmoni prices for 2006 to 2011, the fertilizer cost svings tht could be dded to the per hectre emissions reduction incentive is $73, $97, nd $29 h -1 ($30, $39, nd $12 c -1 ) for smple projects 1, 2, nd 3, respectively. This cretes pyment incentive tht rnges from $31 to $134 h -1 under Tier I nd $29 to $112 h -1 under Tier II methodologies nd cross ll crbon prices. Adding the fertilizer cost svings increses the incentive pyment to point tht is more comprble with the potentil return from hrd red whet s compred to soft white clsses (Tble 5.10). The return over vrible cost of growing hrd red spring whet is pproximtely $113 h -1 greter thn the return over vrible costs for growing soft white spring whet (Tble 5.10; $441 h -1 minus $328 h -1 ). The incentive for switching from hrd red to soft white whet would hve to be similr or greter thn the price premium in order to stimulte doption. CONCLUSIONS & IMPLICATIONS From our review nd rod test of the ACR2 nd VCS protocols, we conclude: Current protocols do not hve emission fctors specific to PNW whet cropping systems nd my drmticlly over-estimte N2O emissions nd potentil N2O reductions. 147

167 o Since regionl emissions fctors for the PNW re not developed, both the ACR2 nd VCS quntifiction methodologies, defult to using the IPCC Tier I defult fctor. As result there re no differences observed between these protocols for the smple projects considered. o Historicl nd current reserch show tht the direct emission fctor for WA cropping systems my be much lower thn 1% of N fertilizer dditions used under IPCC Tier I methodology. In ddition, n erlier study lso showed N2O emissions were not liner function of N rte s is ssumed using IPCC Tier I methodology (Cochrn et l., 1981). Shifting from hrd red to soft white whet clsses hd the gretest per hectre reduction in N2O emissions compred to doption of vrible rte N ppliction. However, the potentil crege for doption of this mngement chnge is limited by the number of cres in hrd red whet production. In contrst, vrible rte N cn be implemented on ll whet cres nd therefore hs the gretest ggregte N2O reduction potentil. For exmple: o In 2011 there were pproximtely 328,500 cres of winter whet nd 171,200 cres of spring whet plnted in Whitmn County, WA where the Cook Agronomy Frm is locted (NASS, 2011). In generl, there tends to be more crege plnted to hrd red spring whet thn hrd red winter whet (Wshington Whet Fcts, ). 148

168 o Vrible rte N mngement could be performed on spring nd winter whet crege resulting in totl of 499,700 cres vilble in Whitmn County (Appendix A-13). The per hectre incentive pyment for N2O emission reduction lone is unlikely to impct N mngement decisions. The incentive is substntilly incresed when the N fertilizer cost svings re included in the per hectre pyment scenrio. Assuming $5 per ton of CO2e offset (1 ton MgCO2e 1 MgCO2e) the difference in incentive would be: o Project 1: $2.7 h -1 lone versus $73 h -1 with N cost svings. o Project 2: $3.6 h -1 lone versus $101 h -1 with N cost svings. o Project 3: $0.8 h -1 lone versus $22 h -1 with N cost svings. Offsets from griculturl N mngement do not pper to be the best tool for GHG mitigtion nd reducing dditions of rective N to the environment. The monetry incentive for griculturl N mngement for N2O emission reductions could be tied to existing conservtion progrms such s the Conservtion Stewrdship Progrm of the USDA-NRCS to improve the return on investing in GHG emissions reduction ctivities. o There my be co-benefits to encourging reduction in N ppliction rte beyond generting GHG emission reductions. For exmple, voided cidifiction of soils nd wter bodies, limiting N leching impcts on ground nd surfce wter qulity, voided ozone destruction, nd reducing the cost of production). Smple projects 1 nd 2 highlight concerns over lekge tht must be considered nd ddressed when dpting existing protocols to PNW cropping systems. A mngement 149

169 chnge from hrd red whet to soft white whet on project lnds cnnot result in the growing of hrd red whet on otherwise soft white crege. o Accepting project ctivities such s those of smple projects 1 nd 2, would hve to be pproched crefully in order to mintin overll whet production for the different whet mrket clsses (i.e., prevent mrket distortion nd prevent shift emissions elsewhere). Tht would crete lekge nd diminish the overll greenhouse gs emission reductions relized by project ctivities (i.e., not rel). o The incentive under smple project 3 is driven by the N fertilizer cost svings regrdless of the crop or mrket clss. The offset credits generted from N2O emission reductions from reducing N fertilizer rte re irreversible. An voided N2O emission cnnot be reversed s is the cse for crbon sequestrtion projects. This mens no future obligtion for frmers enrolled in project mking them more ttrctive to offset purchsers/users. FUTURE CONSIDERATIONS Bsed on our review nd rod test of these protocols, we suggest the following res for further considertion in order to improve the relevnce of griculturl N mngement protocols to PNW drylnd cropping systems: The ccurcy of emission reductions could be improved through development of regionl emission fctors (Tier II or Tier III). This could be chieved through field mesurements nd/or employing existing biophysicl models (e.g., CropSyst or BioErth). The reltionship between N rte nd emissions should be considered in 150

170 developing ccurte emission fctors if quntifiction methodologies continue to estimte N2O emissions bsed on N fertiliztion rte. Development of PNW focused protocol should utilize n groecologicl zone pproch (Huggins et l. unpublished) in developing regionl emission fctors nd evluting GHG emission reductions from project ctivities to better reflect locl conditions nd mngement prctices. This could be informed by the Ecodistrict pproch used in the Albert protocol. Though county level yield-gol bsed N ppliction estimtes re conservtive, field specific N ppliction records nd the sme number of crop yers should be used in quntifying the bseline emissions to reduce uncertinty in the emission reduction estimte. An N2O emission reduction protocol could be strengthened by including dditionl performnce metrics such s the nitrogen use efficiency metric used in the CAR protocol (Removed to Applied (RTA) = N removed/n pplied). This my be dded s monitoring requirement only or implemented s performnce stndrd in ddition to N fertilizer rte reduction. The performnce could require n improvement in nitrogen use efficiency over the bseline nitrogen use efficiency. Decision support to understnd the conditions under which precision griculture ctully reduces N rte without reducing yields (i.e., doption of precision griculture techniques my not reduce N rte). This is especilly importnt for mnging the economic risk of under pplying N. 151

171 REFERENCES CITED Americn Crbon Registry (2010), Americn Crbon Registry Methodology for N2O Emission Reductions through Chnges in Fertilizer Mngement. Winrock Interntionl, Little Rock, Arknss. Brcmort, K Nitrous oxide from griculturl sources: Potentil role in greenhouse gs emission reduction nd ozone recovery. Congressionl Reserch Report R Wshington Printing Office. Broekhoff, D. nd K. Zyl Outside the cp: opportunities nd limittions of greenhouse gs offsets. World Resources Institute. Climte Chnge 101: Cp nd Trde. Pew Center on Globl Climte Chnge nd the Pew Center on the Sttes. Accessed online t on 09/09/2013. Collins, H.P., S. Hile-Mrim, nd S.S. Higgins Greenhouse gs fluxes from Irrigted Sweet Corn (Ze mys L.) nd potto. (solnum tuberosum L.). CSANR Reserch Report Chpter 21. Avilble online t ccessed 8/8/2013). Crouch, J., R. R. Heim Jr., P. Hughes, nd C. Fenimore, [United Sttes]. Regionl Climtes [in Stte of the Climte in 2012 ]. Bull. Amer. Meteor. Soc., 94 (8): S149-S152. Egle, A., L. Olnder, L.R. Henry, K. Hugen-Kozyr, N. Millr, nd G.P. Robertson Greenhouse Gs Mitigtion Potentil of Agriculturl Lnd Mngement in the United Sttes: A Synthesis of the Literture. Report NI R 10-04, Third Edition. Durhm, NC: Nichols Institute for Environmentl Policy Solutions, Duke University. Fiez, T.E., B.C. Miller, W.L. Pn Assessment of sptilly vrible nitrogen fertilizer mngement in winter whet. J. Prod. Agric. 7(1): Fiez, T.E., B.C. Miller, nd W.L. Pn. 1994b. Winter whet yield nd grin protein cross vried lndscpe positions. Agron. J. 86: Huggins, D.R. nd W.L. Pn Key indictors for ssessing nitrogen use efficiency in cerelbsed groecosystems. Specil edition of J. of Crop Prod. 8 (12):

172 Huggins, Site-Specific N mngement for direct-seed cropping systems. In Kruger, C., G. Yorgey, S. Chen, H. Collins, C. Feise, C. Frer, D. Grntstein, S. Higgins, D. Huggins, C. McConnell, K. Pinter, C. Stöckle Climte Friendly Frming: Improving the Crbon Footprint of Agriculture in the Pcific Northwest. CSANR Reserch Report Wshington Stte University. Accessed online 09/10/2013 t Huggins, 2010b.Yield, protein, nd nitrogen use efficiency of spring whet: evluting fieldscle performnce. In Kruger, C., G. Yorgey, S. Chen, H. Collins, C. Feise, C. Frer, D. Grntstein, S. Higgins, D. Huggins, C. McConnell, K. Pinter, C. Stöckle Climte Friendly Frming: Improving the Crbon Footprint of Agriculture in the Pcific Northwest. CSANR Reserch Report Wshington Stte University. Accessed online 09/10/2013 t Huggins et l., unpublished?. Dynmic Agroecologicl Zones for the Inlnd Pcific Northwest, USA. Intergovernmentl Pnel on Climte Chnge Volume 4: Agriculture, Forestry nd Other Lnd Use. Chpter 11: N2O emissions from mnged soils, nd CO2 emissions from lime nd ure ppliction. In 2006 IPCC Guidelines for Ntionl Greenhouse Gs Inventories. De Klein, C., R.S.A. Novo, S. Ogle, K.A. Smith, P. Rochette, nd T.C. Wirth, B. G. McConkey, A. Mosier, nd K. Rypdl. Koenig, R Estern Wshington Nutrient Mngement Guide. Drylnd Winter Whet. EB1987. WSU Extension Publishing nd Printing. Lee, C.M., M. Lzrus, G.R. Smith, K. Todd, nd M. Weitz A ton is not lwys ton: A rod-test of lndfill, mnure, nd fforesttion/reforesttion offset protocols in the U.S. crbon mrket. Environ. Sci. Policy 33: Mhler, R.L. nd S. O. Guy Northern Idho Fertilizer Guide. Soft White Spring Whet. CIS McCool, D.K. nd R.D. Roe Long-term erosion trends on croplnd in the Pcific Northwest. ASAE Section Meeting Pper No. PNW Pcific Northwest Section Meeting, Albert, Cnd September, ASAE, St. Joseph, MI. 153

173 Millr, N., G.P. Robertson, A. Dimnt, R. J. Gehl, P.R. Grce, nd J.P. Hoben Methodology for quntifying nitrous oxide (N2O) emissions reductions by reducing nitrogen fertilizer use on griculturl crops. Americn Crbon Registry, Winrock Interntionl, Little Rock, Arknss. Millr, N., G.P. Robertson, P.R. Grce, R. J. Gehl, nd J.P. Hoben Nitrogen fertilizer mngement for nitrous oxide (N2O) mitigtion in intensive corn (Mize) production: n emissions reduction protocol for US Midwest griculture. Mitig Adpt Strteg Glob Chnge 15: Mull, D.J., A.U. Bhtti, M.W. Hmmond, nd J.A. Benson A comprison of winter whet yield nd qulity under uniform versus sptilly vrible fertilizer mngement. Agric. Ecosys. Enviro. 38: NASS, Wshington s whet vriety 2011 Crop. Ntionl Agriculturl Sttistics Service, Wshington D.C. Pinter, K Enterprise Budgets:District 1 Whet Rottions Under Conventionl Tillge. Avilble online t Accessed 10/11/2013. Pinter, K Enterprise Budgets: District 1 Whet Rottions Under Conventionl Tillge. Avilble online t Accessed 08/01/2013. Pinter, K Enterprise Budgets: District 1 Whet Rottions Under Conventionl Tillge. Personl Communiction. Ppendick, R.I Frming Systems nd conservtion needs in the Northwest Whet Region. Am. J. Alt. Agric. 11(2&3): Rsmussen, P.E., S.L. Albrecht, R.W. Smiley Soil C nd N chnges under tillge nd cropping systems in semi-rid Pcific Northwest griculture. Soil Tillge Res. 47: Smith, P., D. Mrtino, Z. Ci, D. Gwry et l Greenhouse gs mitigtion in griculture. Phil. Trns. R. Soc. B. 363: Stockle, C., S. Higgins, A. Kemnin, R. Nelson, D. Huggins, J. Mrcos, nd H. Collins Crbon storge nd nitrous oxide emissions of cropping systems in estern Wshington: simultion study. J. Soil Wter Conserv. 67(5):

174 United Sttes Deprtment of Agriculture, Nturl Resources Conservtion Service Lnd Resource Regions nd Mjor Lnd Resource Ares of the United Sttes, the Cribben, nd the Pcific Bsin. U.S. Deprtment of Agriculture Hndbook 296 p. USEPA Inventory of U.S. greenhouse gs emissions nd sinks: EPA 430-R Verified Crbon Stndrd Quntifying N2O emissions reductions in griculturl crops through nitrogen fertilizer rte reduction. Methodology VM Wshington Whet Fcts Wshington Whet Commission. 155

175 Tble 5.1. Greenhouse gs offset progrms with griculturl nitrogen mngement protocols in North Americ. Progrm Regionl scope Strt of Progrm Albert Offset System (Albert) Cndin province of Albert Lunched in 2007 Americn Crbon Registry (ACR) Interntionl Founded in 1996 Climte Action Reserve (CAR) U.S. Uncler Verified Crbon Stndrd (VCS) Interntionl Founded in

176 Tble 5.2. Reviewed quntifiction protocols for griculturl nitrous oxide emissions methodology. Progrm Protocol Title Version Albert Quntifiction Protocol for Agriculturl Nitrous Oxide Emissions Reductions. October Version 1.0 ACR ACR1 - The Americn Crbon Registry Methodology for N2O Emission Not specified Reductions through Chnges in Fertilizer Mngement. November ACR ACR2 - Methodology for Quntifying Nitrous Oxide (N2O) Emissions Version 1 Reductions through Reduced Use of Nitrogen Fertilizer on Agriculturl Crops. July CAR Nitrogen Mngement Project Protocol. Jnury Version 1.1 VCS Quntifying N2O Emissions Reductions in Agriculturl Crops through Nitrogen Fertilizer Rte Reduction. Mrch Version

177 Tble 5.3. Eligible Conditions nd Prctices for Agriculturl Nitrogen Mngement Offset Protocols. Protocol ACR1 ACR2 VCS Albert CAR Component Eligible Project Loctions Eligible Project Strt Dte Globl Globl U.S. Cndin province of Albert On or fter 11/1/1997. Cseby-cse prior. On or fter 01/1/2002. On or fter 03/1/2008. Possibly s erly s 01/01/2002. Fertilized griculturl crops On or fter 01/1/2002. North Centrl Region of U.S. Within 6 months of the 1st dy of new cultivtion cycle. Corn Eligible Crop(s) Fertilized griculturl crops Fertilized griculturl crops Fertilized griculturl crops N Input Sources Credited Inorgnic N Fertilizers Y Y Y Y Y Orgnic N Fertilizers Y Y Y Y N Crop Residue N? N N Y N Approved Prctices Regultory Surplus (Additionlity Test) Other Specifictions Pertinent to Quntifiction My include chnges in fertilizer rte, type, plcement, timing, use of timed-relese fertilizers, nd use of nitrifiction inhibitors. Adherence to regionlly dpted Fertilizer N Best Mngement Prctices. Must exceed existing lws, regultions, sttutes, legl rulings, or other regultory frmeworks tht directly or indirectly ffect GHG emissions ssocited with project ction. If project ctivity re nonhomogeneous, must strtify. Eligible crops hve been cultivted from t lest 5 yers prior to strt dte. Adherence to BMPs relted to ppliction of synthetic nd orgnic N fertilizers required (Right source-rtetime-plce). No mndtory lw requiring reduced N input rte below BAU. Encourges doption of economiclly optimum N fertilizer rte. Integrted set of N Best Mngement Prctices - Consistent 4R Nitrogen Stewrdship Pln. Emissions must not be required by lw. All fields must be under project ctivities (4R). Accounts for ll forms of N. The North centrl region includes the following sttes: IL, IN, IA, KS, MI, MN, MS, NE, ND, OH, SD nd WI Also ccept projects beginning on or fter June 27, 2010 until Jn Must decrese synthetic nd/or orgnic N pplied. Only synthetic N credited for emission reductions. Must exceed federl, stte, or locl regultions or other legl mndtes. Encourges use of vrible rte technology nd other dptive mngement strtegies. 158

178 Tble 5.4. Emission Sources nd Sinks Included in Clcultion of Bseline nd Project N2O Emissions by Protocol. Physicl Boundry nd Emissions Sources or Sinks Included Gs ACR1 ACR2 VCS Albert CAR Bseline Activity Direct Emissions from Fertilizer Appliction Indirect Emissions from Fertilizer Appliction (Re-deposition of Voltilized Ammoni, N Leching, nd N Runoff) Emissions from Fossil Fuel Combustion On-Site s Result of N Mngement CO2 N N N N N CH4 N N N N N N2O Y Y Y Y Y CO2 N N N N N CH4 N N N N N N2O Y Y Y Y Y CO2 Y N N Y Y CH4 Y N N N N N2O Y N N Y N Emissions from Fertilizer Production nd Distribution CO2 Y N N N N Soil Crop Dynmics CO2 N N N Y N N2O N N N Y N Project Activity Direct Emissions from Fertilizer Appliction Indirect Emissions from Fertilizer Appliction (Re-deposition of voltilized mmoni, N Leching, nd N Runoff) Emissions from Fossil Fuel Combustion On-Site s Result of N Mngement CO2 N N N N N CH4 N N N N N N2O Y Y Y Y Y CO2 N N N N N CH4 N N N N N N2O Y Y Y Y Y CO2 Y N N Y Y CH4 Y N N N N N2O Y N N Y N Emissions from Fertilizer Production nd Distribution CO2 Y N N N N Soil Crop Dynmics CO2 N N N Y N N2O N N N Y N The ACR1 protocol does not include N 2 O emissions from runoff for quntifiction of indirect N 2 O emissions. Emissions from fertilizer production included in quntifiction but emissions from fertilizer distribution re not included. Soil Crop Dynmics includes the emissions of CO 2 nd N 2 O from the cycling of soil nd plnt N. This includes N deposition in plnt tissue (residue), decomposition of crop residues, nd stbiliztion in orgnic mtter. 159

179 Tble 5.5. Quntifiction Approches for Bseline nd Project Emissions. Protocol ACR1 ACR2 VCS Albert CAR Prmeter Bseline N 2 O Emission Clcultion Crop Yers used in Bseline N Rte Determintion Bseline Dt Source Project N 2 O Emissions (Additionlity Test) Lekge Continution of pre-project fertilizer mngement. Bseline emissions clculted using DNDC model. Previous 5 yers of specified crop Uncler Project emissions clculted using DNDC model Yield cnnot decline more thn 5%; no increse in fertilizer use outside project boundries Business s usul N mngement. Determined from: 1. Site-specific records or 2. county-level yield dt nd N fertilizer guides Monoculture:5 yers 2 yer Rottion: 3 cycles (6 yrs) 3 Yer Rottion: 2 cycles (6 yrs) Field-Specific or Stte/County Dt Reduce N rte from Business s usul on sme crop s bseline Lekge considered negligible for project ctivities Bseline Emissions Business s usul N mngement. Determined from: 1. Site-specific records or 2. county-level yield dt nd N fertilizer guides Monoculture:5 yers 2 yer Rottion: 3 cycles (6 yrs) 3 Yer Rottion: 2 cycles (6 yrs) Field-Specific or Stte/County Dt Project Emissions Must exceed Business As Usul N rte for the specific crop(s). Lekge considered negligible for project ctivities Site-Specific Averge N Rte prior to strting project ctivities. Previous 3 yers of ech crop Field specific Emission reduction under bsic, intermedite or dvnced level of 4R Consistent Pln. Crop by Crop bsis. Must ccount for incresed emissions from project ctivities tht increse trips cross field (e.g., split N) At lest 3 nd up to 5 yers Field Specific Reduce N rte, emissions bsed on MSU-EPRI methodology Must ccount for N 2 O, CO 2, nd CH 4 if yield decline results in incresed GHG emissions from shifted production 160

180 Tble 5.6. Comprison of Approches for Clculting Direct nd Indirect N2O Emissions. Emission Source/Sink ACR1 ACR2 VCS Direct N2O from Fertilizer DNDC 1- MSU-EPRI eqn IPCC Tier I IPCC Tier I 2- MSU-EPRI eqn. 3- IPCC Tier II Indirect N2O Emissions 2006 IPCC Guidelines Voltiliztion with subsequent re-deposition Frction of Synthetic N Fertilizer Voltilized 0.10 Emission fctor for N2O emission from tmospheric deposition of voltilized N on soil 0.01 nd wter surfces Leching nd Runoff Frction of Synthetic N Fertilizer Leched 0.30 Emission fctor for N2O emission from N leching nd runoff Millr et l.,

181 Tble 5.7. Direct nd Indirect Emissions for Bseline nd Project Conditions under Tier I nd Tier II Approches for Quntifying Direct N2O Emissions. Tier I Tier II Emissions Reduction Rte, Mg CO 2 e h -1 yr Project 1 Project 2 Project 3 Project 1 Project 2 Project 3 Bseline Emissions Direct Indirect Bseline Totl Project Emissions Direct Indirect Project Totl N 2 O Emissions Reduction Smple Projects 1 nd 2 represent emission reductions using field specific N ppliction dt. A meggrm (Mg) is equivlent to metric ton (t). 162

182 Tble 5.8. Nitrous Oxide Emission Reduction Potentil nd Offset Credit Incentive for the Agriculturl N Mngement Smple Projects. Smple Project Scenrio N2O Emission Reduction Rte Totl Are Totl Potentil Emissions Reduction Per Are Monetry Incentive for N2O Emission Reductions by Offset Price Mg CO 2 e h -1 yr -1 h Mg CO 2 e yr $ h -1 yr Price per Mg CO 2 e $5 $10 $50 Tier 1 Direct Emission Fctor (1%) 1- HRWW to SWWW HRSW to SWSW Uniform to Vrible Rte Regionl Emission Fctor (0.2%) HRWW to SWWW HRSW to SWSW Uniform to Vrible Rte Emission reductions clculted using field specific N fertiliztion dt from the Cook Agronomy Frm Cropping System Reserch Field (37 h or 90 c). For 33 kg N h -1 reduction in N fertiliztion rte. 163

183 Tble 5.9. Including the Fertilizer Cost Svings for Clculting the Offset Credit Incentive for the Agriculturl N Mngement Smple Projects tht Reduce N2O Emissions. Smple Project Scenrio Tier 1 Direct Emission Fctor (1%) N2O Emission Reduction Rte Mg CO2e h -1 yr -1 Monetry Incentive for N2O Emission Reductions Averge Expected Fertilizer Cost Sving Totl Monetry Incentive (N2O Offset Credit + N Fertilizer Cost Svings) $ h -1 yr -1 $ h -1 $ h -1 yr -1 Price per Mg CO2e Price per Mg CO2e $5 $10 $50 $5 $10 $50 1- HRWW to SWWW HRSW to SWSW Uniform to Vrible Rte Regionl Emission Fctor (0.2%) HRWW to SWWW HRSW to SWSW Uniform to Vrible Rte Bsed on verge nhydrous mmoni costs from 2006 to 2011 (Appendix Tble E.2). 164

184 Tble Pyment Incentive of Smple Project Activities Reltive to Returns over Whet Production Costs. Smple Project Scenrio Tier 1 Direct Emission Fctor (1%) N2O Emission Reduction from Project Activities Totl Incentive by Offset Price Scenrio (Offset Credits + Cost Svings) Return over Vrible Cost Mg CO2e h -1 $ h -1 yr -1 $ h -1 Price per Mg CO2e $5 $10 $50 Project 1: HRWW to SWWW White Winter Whet 671 (272) Hrd Red Winter Whet Project 2: HRSW to SWSW White Spring 328 (133) Hrd Red Spring 441 (179) Project 3: Vrible Rte N SWWW Regionl Emission Fctor (0.2%) Project 1: HRWW to SWWW White Winter Whet 671 (272) Hrd Red Winter Whet Project 2: HRSW to SWSW White Spring 328 (133) Hrd Red Spring 441 (179) Project 3: Vrible Rte N SWWW Averge from three yers (2009, 2011, nd 2012) of regionl enterprise budgets (Pinter). 165

185 Figure 5.1 Emission estimtes from EPA Inventory of U.S. Greenhouse Gs Emissions nd Sinks from by ) mjor U.S. economic sector nd b) N2O emission sources (USEPA, 2013). 166

186 Figure 5.1. Emissions for Smple Projects 1 nd 2 by Protocol nd Bseline Quntifiction Approch. For quntifiction the IPCC Tier I emission fctor ws used for direct emissions nd IPCC defult emission fctors for indirect emissions in both smple project 1 (left) nd smple project 2 (right). 167

187 Figure 5.3. Emissions for Bseline nd Project Activities under ACR2 nd VCS Quntifiction Methodologies. Tier I IPCC direct emission fctor nd IPCC defult indirect emission fctors used. Field specific N ppliction records were used to quntify emissions reductions represented in this figure. 168

188 Figure 5.4. Offset Credits for Project Activities under Tier I nd Tier II Direct N2O Emission Fctors. The IPCC Tier I defult (blue) nd potentil Tier II emission fctor (red). Tier I is 1% nd Tier II is 0.2% of N fertilizer pplied. These dt represent only the field specific N ppliction dt for smple projects 1 nd

189 CHAPTER 6 CONCLUSIONS The response of grin yield, grin protein concentrtion, hrvest index (HI) nd test weight (TWT) to N rte tretments nd spikes m -2 vried by yer nd lndscpe but it ws noted tht hying-off likely occurs in most yers in south bckslope nd summit positions. Mngement induced hying-off ppers to contribute to grin yield declines in these drier lndscpe positions nd especilly during low precipittion yers. Test weight, s proxy for kernel mss, proved to be strong indictor in the yers where hying off ws more strongly expressed. The spikes m -2 (SPM) ppered to be better predictor of yield response thn ctul plnt popultion. However, mnging for optimum SPM will require knowledge of the tillering chrcteristics nd compenstion mong yield components under frm specific mngement prctices nd environmentl conditions. The use of nd breeding for vrieties with reduced tillering will be needed to mnge for SPM. In ddition, the expression of hying-off in yield components (e.g., kernel mss) nd reltionship to more esily obtined yield qulity mesures should be explored further. One of the most surprising findings of this reserch ws the overll lck of significnt NR by SR interctions for the different dependent vribles considered in this reserch. Wether conditions vried considerbly from yer to yer but lndscpe remined significnt effect on the vilble wter, biomss nd nitrogen use efficiency (NUE) prmeters evluted. Nitrogen rte mngement should be trgeted first to void hying-off given tht N rte hd greter impct on vegettive biomss nd depletion of vilble soil wter resources t nthesis. 170

190 However, it ws observed tht the highest nthesis biomss nd soft white winter whet NUE trgets could be chieved with 34 to 68% reduction in typicl seeding rtes used t the Cook Agronomy Frm. This reserch expnds the lndscpe scle understnding of NUE by highlighting tht differences in NUE mong wet versus drier lndscpe positions is most ssocited with reducing N losses in wet conditions nd overcoming wter-stress induced limittions on N loss s well s N utiliztion efficiency in drier conditions. The incrementl grin yield or NUE increse with N rte or seed rte tretments ws not evluted in this reserch. This is needed to identify economiclly optimum yields nd the role of different NUE components tht contribute to yield or NUE response. The NUE performnce clssifiction developed in this reserch ws successful in cpturing environmentl nd mngement fctors contributing to the lrge vribility in NUE s observed. Site-specific N mngement should consider strtegies such s split-n pplictions to djust N supplies to growing seson conditions nd crop N demnd in order to improve NUE nd reduce the risk for hying-off. Mngement zone pre-plnt soil smpling for residul N will be importnt for voiding hying-off s high pre-plnt residul inorgnic N cn contribute to excessive N supply nd potentilly hying-off. Furthermore, pre-plnt inorgnic N cn exhibit substntil vribility cross yers nd lndscpe positions. The reltionship between pre-plnt N sttus, crop N sttus t nthesis, nd the chnge in vilble wter nd biomss ccumultion between nthesis nd mturity were not evluted in this reserch. Future reserch should incorporte these to identify the rnge of conditions or contributing fctors to 171

191 hying-off. An dditionl considertion for this dt set is the positionl vilbility of wter nd N resources within the soil profile throughout the growing seson for the different lndscpe positions nd tretments. Vrible rte N mngement cn be implemented in ll crop yers nd on ll whet cres in the PNW, creting considerble N2O reduction potentil on ggregte. The per hectre incentive pyment for N2O emission reduction lone ws not found to be lrge enough to impct site-specific N mngement doption but the incentive ws substntilly incresed when the N fertilizer cost svings were included in the per hectre pyment. From this reserch it ws concluded tht site-specific mngement offers prcticl mngement strtegy to trget inputs to wether nd lndscpe specific environmentl conditions. Vrible rte mngement hs the potentil to mintin or increse winter whet yield with fewer N or seed inputs while lso providing ecosystem services such s GHG emission reductions, reducing N leching impcts on ground nd surfce wter qulity, nd decresing the rte of soil cidifiction in PNW griculturl soils. 172

192 APPENDIX A-1. Methodology for ll site yers tht is pplicble to Chpters 2, 3 nd 4 of the disserttion. Field plot trils were conducted during the 2010, 2011 nd 2012 winter whet hrvest yers to evlute N fertilizer nd seeding rte effects on soft white winter whet yield, yield qulity, nd yield components t the Cook Agronomy Frm (CAF), ner Pullmn, WA (Figure 1). The Cook Agronomy Frm is 37 h (92 c) drylnd cropping systems reserch frm tht ws estblished in The frm hs been mnged under direct-seeding since 1998 with conditions representtive of typicl estern Plouse lndscpe. The frm is in high rinfll zone (550 mm) nd primrily mnged under three yer cerel rottion (e.g., winter whetspring whet-spring legume). Winter whet ws the focus crop for ll three site yers of this reserch. In ech field within the CAF (i.e., site yer), plot res were selected to represent different components of the hillslope profile s described by the Ruhe clssifiction system (Hll nd Olson, 1991). Plot plcement of the different hillslope positions were bsed on historicl yield gol (Figure 1c) nd soil properties for the frm (Figure 1b) (Soil Survey Stff, 2013; Huggins et l., 2014). The hillslope profile components will be referred to s lndscpe positions for the reminder of this document. Cook Agronomy Frm Site Yer: 2010 (Field C) The entire field, including plots, were plnted to the winter whet vriety OR102. The winter whet ws plnted in pired rows on 12 inches centers using no-till drill (Horsh- Anderson) equipped with hoe type openers. The previous crop ws hrd red spring whet ( Hnk ). Plnt popultion counts were performed in the spring of 2010 by counting plnts in 173

193 three 1-m lengths of row from the center of ech plot. Spike counts were performed between lte nthesis (Feekes 10.5) nd mturity (Feekes 11.4) in August of Totl bove ground biomss nd biomss N content were determined from hnd hrvested smples collected t mturity from 1 m 2 re in the center of ech plot. The north nd south slopes were composed of Plouse silt lom soils (fine-silty, mixed, superctive, mesic Pchic Ultic Hploxerolls) nd the summit ws Nff silt lom soil (fine-silty, mixed, superctive, mesic Typic Argixerolls) (Tble 1, Soil Survey Stff, 2013). Study 1: Plnt Density Experiment with Uniform N Plots were estblished on north nd south slope position tht hd been uniformly seeded (240 seeds m -2 ) to winter whet under uniform N fertilizer rte (112 kg N h -1 ) using ure mmonium nitrte in the Oct. of A strter ppliction of liquid mmonium polyphosphte ( ) nd thiosol ( ) ws bnded with the seed for ll plots (including the control) t rte of 8.5 kg N h -1, 5 kg P h -1 nd 11 kg S h -1. The winter whet plnts were counted in 3m 2 plots nd then thinned to chieve three plnt popultion tretments of 98, 164, nd 230 plnts m -2 in the spring of However, the highest plnt density tretment (230 plnts m -2 ) ws rrely chieved due to low plnt popultion under the uniform seeding rte of 240 seeds m -2 (Fig. 4b). The plnt density tretments were replicted four times in ech lndscpe position. Study 2: 2010 Nitrogen Rte X Plnt Density Experiment A nitrogen rte x seeding rte experiment ws initited on winter whet tht hd been plnted under vrible rte N mngement in October of The rndomized complete block 174

194 split plot design ws imposed on south fcing bckslope (four replictions) nd summit (two replictions) lndscpe position. Nitrogen fertilizer rtes of 0, 48, 76, nd 104 kg N h -1 were obtined using ure mmonium nitrte solution (32-0-0). A strter ppliction of liquid mmonium polyphosphte ( ) nd thiosol ( ) ws bnded with the seed for ll plots (including the control) t rte of 8.5 kg N h -1, 5 kg P h -1 nd 11 kg S h -1. Uniformly seeded (240 seeds m -2 ) N fertilizer rte plots on south nd summit lndscpe position were thinned to chieve plnt popultion tretments of 98, 164, nd 230 plnts m -2 within ech N fertilizer tretment (Figure 1). However, the highest plnt density tretment (230 plnts m -2 ) ws not chieved due to low plnt popultion under the uniform seeding rte of 240 seeds m -2 (Fig. 6c). Ech N rte by plnt density plot ws 3 m 2 in size. Study 3: Nitrogen Rte Experiment with Uniform Plnt Density An N rte plot scle experiment in the north, summit, nd south slope lndscpe positions ws initited in the spring of 2010 within lrger field-scle N rte study. The field ws seeded t uniform rte of 240 seeds m -2 nd N fertilizer ws pplied t 0, 48, 76, nd 104 kg N h -1 using ure mmonium nitrte (32-0-0) t ech geo-referenced grid point cross the field in Oct A strter ppliction of liquid mmonium polyphosphte ( ) nd thiosol ( ) ws bnded with the seed for ll plots (including the control) t rte of 8.5 kg N h -1, 5 kg P h -1 nd 11 kg S h -1. There were four replictes for north nd south slopes nd two replictes for the summit position. Replictes for the summit position were limited by the smll size of the summit lndscpe position for this prticulr field t CAF. Cook Agronomy Frm Site Yers: 2011(Field B) nd 2012 (Field A) 175

195 In 2011 nd 2012 rndomized complete block split plot design with N fertilizer rte s the min plot nd winter whet seeding rte s the subplot ws estblished on three different lndscpe positions. The tretment combintions were replicted four times t ech lndscpe position. Lndscpes with different yield gol nd soil chrcteristics were selected from reltive yield ( ; Huggins, 2010), field soil survey, nd soil orgnic mtter mps (Huggins nd Uberug, 2010) such s those in Figure 1b nd c. The lndscpe positions included res of high, intermedite, nd low reltive yield tht were generlly locted on north fcing bckslope (north slope), footslope nd south fcing bckslope (south slope) positions, respectively, (Ruhe, 1960 in Hll nd Olson, 1991). The south nd north slopes re described s Plouse silt lom soils (fine-silty, mixed, superctive, mesic Pchic Ultic Hploxerolls) (Tble 1, Soil Survey Stff, 2013). The footslope position is described s Thtun silt lom (fine-silty, mixed, superctive, mesic Oxyquic Argixerolls) (Soil Survey Stff, 2013). The plots were seeded nd fertilized on 19 cm (7.5 in) row spcing using Fbro no-till double disk plot drill with totl min plot size of 35 m 2 nd subplot size of 8.75 m 2. An ppliction of mmonium phosphte sulfte strter fertilizer ( ) ws bnded with the seed in ll plots t rte of 13 kg N h -1, 7 kg P h -1 nd 12 kg S h -1. Nitrogen fertilizer (dry ure, ) ws estblished s the min plot nd bnd pplied below the seed t plnting t rtes of 0, 40, 80, 120, nd 160 kg N h -1. Plnt popultion nd spike density differences were estblished within ech NR strip by seeding t 80, 165, 250, nd 335 seeds m -2. Soft white winter club whet ( Chukr ) ws plnted on October 13 in both 2011 nd Seed weight nd kernels per pound were determined ech yer to clculte the mount of seed weight 176

196 required to chieve the desired seeding rtes. The previous crop ws grbnzo bens (Cicer rietinum, Sierr ). Pesticides pplictions were mnged similr to the bulk field using bckpck spryer. Hnd weeding ws performed in plots tht experienced significnt weed pressure. Plnt popultion ws determined t hrvest in 2011 by counting plnts collected from 1-m length of row in the middle of ech plot. In 2012 plnt popultion ws determined from stnd counts in three 1-m lengths of row prior to tillering (Feekes 2.0). Spike counts nd plnt height mesurements were performed between nthesis (Feekes 10.5) nd mturity (Feekes 11.4). Spike counts were performed on 1-m lengths of row t three loctions in the middle of ech plot to determine the spike density (number of spikes m -2 ). Totl bove ground biomss nd biomss N concentrtion were determined on hnd hrvested smples collected from 2- m 2 re t mturity. All Site Yers Aboveground biomss subsmples were weighed nd threshed using sttionry thresher to determine grin yield, kernels per spike nd kernel mss. Kernels per spike were clculted by dividing totl kernel mss by individul kernel mss nd the totl number of spikes. Residue biomss subsmples were ground to pss 2-mm sieve (Wiley Mill) nd nlyzed for totl N by dry combustion (Leco TruSpec CN, Leco Corportion, St. Joseph, MI). Grin protein nd moisture concentrtion were determined by ner infrred reflectnce (Infrtec 1241 Grin Anlyser, FOSS, Denmrk). Kernel weights were determined on 1000,

197 nd 500 seed counts in 2010, 2011 nd 2012, respectively. Grin yield is expressed t 12% wter content nd plnt N s oven dry (60 C) weight. Soil smples for grvimetric wter nd inorgnic N were collected t 30 cm increments to depth of 150 cm in the (i) spring of 2010; (ii) fll of 2011 prior to plnting; (iii) fll of 2012 prior to plnting; nd (iv) s soon s possible following hrvest for ll yers using Giddings probe (3.70 cm inside dimeter). Grvimetric wter content ws determined by oven drying smples t 105 C for 24 hours. Soil inorgnic N concentrtion (NO3 - -N plus NH4 + -N) ws determined using 2M KCl extrction procedure with inorgnic N nlysis performed on continuous flow nlyzer (Mynrd et l., 2008). Twenty-five mls of 2M KCl ws dded to 6 grms of soil nd then shken for 1 hour. The superntnt ws filtered by pouring through n 8µm (Whtmn No. 2) or 25µm filter (Fisher P8). The filtrte ws frozen until nlysis for totl inorgnic N s NO3 - nd NH4 + on n utomted spectrophotometer (Lcht QuickChem FIA series, Lcht Instruments, Lovelnd, CO). Net N minerliztion ws clculted from control plots (0 kg N fertilizer h -1 ) using the pproch of Huggins nd Pn (2003) s shown in eqution 1. The N supply ws estimted from sum of pre-plnt residul N (Nr), estimted net N minerliztion (Nmin) nd N fertilizer ppliction rte (Nf) (eq. 2). Estimted net N minerliztion from control plots, Nmin = [(Nt +Nh) (Nr+Nstrter)] [Eq 1] Where: Nt is totl plnt N t hrvest, kg N h -1 Nh is totl inorgnic N in soil t hrvest, kg N h -1 Nr is the totl inorgnic N in the soil prior to plnting, kg N h -1 Nstrter is N fertilizer dded s strter, kg N h -1 Nitrogen Supply, N s = N r + N min + N f [Eq 2] Where: 178

198 Nr is the totl inorgnic N in the soil prior to plnting, kg N h -1 Nmin is N minerliztion from Eq. 1, kg N h -1 Nf is N fertilizer ppliction rte including strter, kg N h -1 This estimtion of N minerliztion ssumes no loss of soil or plnt N in the control plots nd tht ddition of N fertilizer does not impct net minerliztion. The Nmin estimtion ssumes there re no losses of pre-plnt residul inorgnic N (Nr) or other N sources such s depositionl N (Nd) nd fixed N (Nx) from the control plots. For this reserch, Nx nd Nd were considered to be miniml nd were not included the estimte of Nmin. Overll these ssumptions would result in n underestimtion of the N supply since N minerliztion clculted from control plots includes immobiliztion nd is therefore net minerliztion (Huggins nd Pn, 1993). Avilble soil wter content ws determined from tillering, nthesis, nd post-hrvest grvimetric soil wter content mesurements. Soil bulk density estimtes from nerby georeferenced monitoring loctions were used to convert grvimetric moisture to volumetric moisture content (cm 3 cm -3 ). The volumetric moisture content ws then multiplied by the soil profile depth (i.e., 30 cm) nd then summed over the soil profile s pproprite for individul chpters. The vilble soil wter ws determined ssuming 110 g kg -1 grvimetric wter concentrtion t the permnent wilting point (Fiez et l., 1994b). Dily precipittion nd temperture dt ws obtined from the NOAA Ntionl Wether Service Pullmn 2 NW (46 46 N, W) locted t the nerby Plouse Conservtion Field Sttion, Pullmn, WA. The vilble soil wter blnce ws clculted s the sum of vilble wter in the surfce 150 cm of soil plus precipittion occurring between smpling events. This included vilble wter t 179

199 tillering (Tv), nthesis (Av), nd mturity (Mv). Consumptive wter use ws determined between: (i) tillering nd nthesis (TACWU); (ii) nthesis nd mturity (AMCWU); nd (iii) tillering nd mturity (TMCWU). Consumptive wter use between developmentl stges ws determined by subtrcting the vilble wter between stges nd dding the precipittion between the stges (Eq. 3). Wter use efficiency (WUE), defined here s the rtio of grin yield to wter use, ws estimted by dividing grin yield (kg h -1 ) by the TMCWU (cm) following the method of Angus nd vn Herwrden (2001). Consumptive Wter Use, cm = [Av1 Av2] + Precipittion12 [Eq 3] Where: Av1 is the vilble wter t developmentl stge 1, (e.g., Tillering), cm Av2 is the vilble wter t developmentl stge 2, (e.g., Mturity), cm Precipittion12 is the totl precipittion occurring between stges 1 nd 2, cm Growing degree dys (GDD), in degrees Celsius, were used to determine het ccumultion from plnting to hrvest. Dily GDD were clculted s the verge of the high nd low ir tempertures (in C) for ech dy nd verge GDD vlues below freezing were given vlue of zero (Krow et l., 1993). Cumultive growing degrees dys were tken s the ccumulted GDD from plnting to hrvest, Growing Degree Dy, C = {(Tmx + Tmin)/2} - 0 C [Eq 4] Where: Tmx is mximum dily temperture in C Tmin is minimum dily temperture in C 180

200 A-2. Field plot loction t the Cook Agronomy Frm Plot () nd supporting dt for site selection of soil orgnic crbon contents for surfce 30-cm (b) nd reltive yield mps from hrvest yers (c). b c 181

201 A-3. Cumultive monthly precipittion () nd growing degree dys using 0 C bse (b) for ech site yer s compred to norml. Cumultive precipittion (cm) compred to norml precipittion ( ) for Oct. 1 to Sept. 30 using NOAA Ntionl Wether Service Pullmn 2 NW (46 46 N, W) locted t the Plouse Field Conservtion Field sttion, ner Pullmn, WA. Month Norml Cumultive Precipittion, cm October November December Jnury Februry Mrch April My June July August September Cumultive Growing Degree Dys, C October November December Jnury Februry Mrch April My June July August September

202 A : regression equtions, djusted r 2 nd probbilities. Only liner or qudrtic trends were tested for significnce t the 10% level. Study Independent Dependent Regression Eqution Adj. r 2 Pr>t Pr>t Vrible Vrible Lndscpe X X 2 1: Plnt Density Experiment with Uniform N Spikes m -2 NBS TWT X X SBS GW X n GPR X n HI X n TWT X 2 : Nitrogen Rte X Plnt Density Experiment Nitrogen Rte, kg h -1 SBS GPR X X <.0001 <.0001 HI X <.0001 n SU GPR X X HI X X TWT X X n Spikes m -2 SBS GPR X X HI X X SU GPR X <.0001 n 3: Nitrogen Rte Experiment with Uniform Seeding Rte Nitrogen Rte, kg h -1 NBS GPR X n HI X n SBS GW X -0.16X GPR X <.0001 n HI X n TWT X n SU HI X X Abbrevitions for vribles: NBS, north bckslope; SBS, south bckslope; SU, summit; Gw, grin yield; GPR, grin protein; HI, hrvest index; nd TWT, test weight. n, not pplicble. 183

203 A : regression equtions, djusted r 2 nd probbilities. Only liner or qudrtic trends were tested for significnce t the 10% level. Independent Dependent Regression Eqution Adj. r 2 Pr>t Pr>t Vrible Vrible Lndscpe X X 2 Nitrogen Rte, kg h -1 NBS FS SBS Spikes m -2 NBS FS GW X <.0001 n GPR X <.0001 n HI x x TWT X n GW X n GPR X n HI X n GW X <.0001 GPR X X < TWT X X < GW X <.0001 n HI X n GW X <.0001 n GPR X n HI X n TWT X <.0001 n SBS GW X-0.017X GPR X n HI X X TWT X X Abbrevitions for vribles: NBS, north bckslope; SBS, south bckslope; FS, footslope; Gw, grin yield; GPR, grin protein; HI, hrvest index; nd TWT, test weight. n, not pplicble. 184

204 A : regression equtions, djusted r 2 nd probbilities. Only liner or qudrtic trends were tested for significnce t the 10% level. Independent Dependent Regression Eqution Adj. r 2 Pr>t Pr>t Vrible Vrible Lndscpe X X 2 Nitrogen Rte, kg h -1 NBS Spikes m -2 FS SBS NBS FS GW X X < GPR X n HI X <.0001 n GW X n GPR X n HI X n GW X X TWT X <.0001 n GW X X GPR X X HI X <.0001 n GW X X < GPR X X <.0001 <.0001 HI X n SBS GW X <.0001 n GPR X X HI X X Abbrevitions for vribles: NBS, north bckslope; SBS, south bckslope; FS, footslope; Gw, grin yield; GPR, grin protein; HI, hrvest index; nd TWT, test weight. n, not pplicble. 185

205 A-7. Nitrogen use efficiency nd components terminology. Descriptor Symbol Components Grin Yield Gw Non-grin Aboveground Hw Biomss N Supply Ns (Nr+Nmin from control plots) + Nf ; cn be estimted s Nt+Nh (control plots) + Nf; Nf+Nr+Nm+Nx+Nd Aboveground N in plnt t Nt physiologicl mturity Pre-plnt N Nr Post-Hrvest N Nh N minerlized from soil orgnic Nmin mtter Grin N Ng Fertilizer N pplied Nf Plnt vilble N Nv Estimted s Nv=Nt+Nh; Nv=Ns-(Nim+Nl+Ner+Ngl+Ncf) N use efficiency Gw/Ns (Nv/Ns)(Gw/Nv)=(Nf/Ns)(Gw/Nf) N uptke efficiency Nt/Ns (Nt/Nv)(Gw/Nt) Plnt Avilble NUE Gw/Nv (Nt/Nv)(Gw/Nt) N retention efficiency Nv/Ns N utiliztion efficiency Gw/Nt Avilble N uptke efficiency Nt/Nv Grin N ccumultion efficiency Ng/Ns (Ng/Nv)(Nv/Ns)=(Ng/Nf)(Nf/Ns) N hrvest index Ng/Nt N trnsloction efficiency N relince index Nf/Ns N fertilizer use efficiency Gw/Nf N blnce index Ng/Nf (Nlo/Nf)(Ng/Nlo) Unit N requirement Ns/Gw Tble dpted from Dwson et l. (2008) nd Huggins et l. (2010b). 186

206 A-8.Nitrogen nd seeding rte effect on winter whet biomss, surfce vilble wter nd subsurfce vilble wter t nthesis by lndscpe for Lndscpe nd Tretment Biomss t Anthesis Avilble Wter Surfce Subsurfce North Bckslope N Rte, kg N h d cd bc 3.50 b b 2.45 bc c 8.42 Seeding Rte, seeds m b b b b 9.20 N Rte < < Seeding Rte < N Rte*Seeding Rte Footslope N Rte, kg N h c bc bc b Seeding Rte, seeds m N Rte Seeding Rte N Rte*Seeding Rte South Bckslope N Rte, kg N h c b bc b b 2.31 b b 1.55 bc 6.13 bc c 4.43 c Seeding Rte, seeds m b b N Rte < < < Seeding Rte N Rte*Seeding Rte Totl boveground biomss t nthesis. Surfce nd subsurfce vilble wter content is for 0 to 90-cm nd 90 to 150-cm. 187

207 A-8b. Nitrogen nd seeding rte effect on NUE, GW/Nt, nd Nt/Ns for winter whet by lndscpe for

208 A-9. Nitrogen nd seeding rte effect on winter whet biomss, surfce vilble wter nd subsurfce vilble wter t nthesis by lndscpe for Lndscpe nd Tretment Biomss t Anthesis Avilble Wter Surfce Subsurfce North Bckslope N Rte, kg N h d c 4.99 b b b 4.35 b c b c 9.98 b Seeding Rte, seeds m b b N Rte < < Seeding Rte N Rte*Seeding Rte Footslope N Rte, kg N h Seeding Rte, seeds m b b N Rte Seeding Rte N Rte*Seeding Rte South Bckslope N Rte, kg N h c bc b b b 3.31 b 5.15 Seeding Rte, seeds m b b b N Rte Seeding Rte N Rte*Seeding Rte Totl boveground biomss t nthesis. Surfce nd subsurfce vilble wter content is for 0 to 90-cm nd 90 to 150-cm. 189

209 A-9b. Nitrogen nd seeding rte effect on NUE, GW/Nt, nd Nt/Ns for winter whet by lndscpe for

210 A-10. Additionl Informtion on N2O Emission Protocol Fetures Reltive Mrket Shre of Offset Credits by GHG Offset Progrm. Progrm Offset Credits Registry Website Issued Mg CO 2 e Americn Crbon Registry 37,516,575 Climte Action Reserve 34,805,300 Verified Crbon Stndrd 127,537,351 Albert Offset System 48,158,109 As of 6/25/2013 from websites. 1 Mg is 1 metric ton. 191

211 10.2. All Reported Defult Fctors for Quntifying N2O Emissions by Protocol. Emission Source/Sink ACR1 ACR2 VCS N2O GWP N2O from fertilizer DNDC 1- MSU-EPRI eqn IPCC Tier I IPCC Tier I 2- MSU-EPRI eqn 3- IPCC Tier II Frction of synthetic N fertilizer voltilized Emission fctor for N2O emission from tmospheric deposition of N on soil nd wter surfces Frction of N fertilizer pplied tht is leched Emission fctor for N2O emission from N leching nd runoff Emission for Fuel Type Gsoline DNDC? n/ n/ Diesel DNDC? n/ n/ Net Clorific Vlue of Fuel Gsoline DNDC? n/ n/ Diesel DNDC? n/ n/ Emission fctor from the production of fertilizer pplied Ure 1.54 n/ n/ Other N (N content fertilizer)*0.82*2.014 n/ n/ 192

212 A-11. N Fertilizer Dt Needed for Clcultion of N2O Emissions Dt Sources nd Assumptions for Bseline N2O Emissions Quntifiction. Dt Dt Source Assumptions Smple Projects 1 nd 2 Winter nd Spring Whet Yield Field Level- 13 yer cropping history of the Cook Agronomy Reserch Frm, ner Pullmn, WA County Level- USDA-Ntionl Agriculture Sttistics Service website Field Specific N Fertilizer Rte Field Level- 13 yer cropping history of the Cook Agronomy Reserch Frm, ner Pullmn, WA County Level- Clculted From Fertilizer Guides Smple Project 3 N Fertilizer Rte Reduction N rte reduction potentil using vrible N requirement from Fiez et l., 1994 Project Strt Dte of Crop Yer Rottion: WW-SW- Legume Site-Specific N reduces overll N rte. All Projects Whet Production Acreges Economic Dt The whet crege nd production crege by whet clss cme from NASS nd Wshington Whet Commission Report. Cook Agronomy Frm Enterprise Budgets 193

213 11.2. Field Specific N Fertiliztion Rte nd Yield Dt from the Cook Agronomy Frm Dtbse. Crop Rnge in Actul N Fertilizer Rte Yield Rnge kg N h -1 kg h -1 Low High Averge Low High Averge Winter Whet Red White Spring Whet Red White Hrd red winter whet verge yield nd N rte clculted from CAF over 2001 to Hrd red spring whet verge yield nd N rte clculted from CAF over 1999 to Soft white verge yield nd N rte dt from 2010 nd 2011 t CAF. ****Hrd red numbers should probbly come from the 2 yers prior. I need to double check tht this longer term verge is vlid for field specific dt for these quntifiction protocols. It mens the county level yield dt does not cover the sme mount of time (1/9/2015). **** 194

214 11.3. Yield Gol Bsed N Rte Clcultion for County Level Dt Approch Yield Gol UNR N Supply Needed Soil N Sources (Credits) N Needed for Residue Decomposition Bu lbs N bu -1 lbs N c -1 lbs N c -1 lbs N c -1 lbs N c - Yield Gol *UNR Soil Inorgnic N Previous Legume Credit Minerliztio n from Orgnic Mtter (15 to 20lbs N *%OM) N Fertilizer to Apply 1 kg h -1 HRWW SWWW HRSW SWSW Clcultion 1. Yield Gol Yield gol cn be determined from grower knowledge, mesured historic verges, preplnt soil moisture nd expected rinfll. For this pproch the Ntionl Agriculture Sttistics Services Quik Stts were used to develop the yield gol bsed on 3 yer rottion of WW-SWlegume. As specified in the protocol, the previous 2 yers of county level yield dt ws used to generte n verge yield gol (Tble B.4). 195