Soil Nitrogen and Carbon Management Project John E. Sawyer Mahdi Al-Kaisi Daniel Barker Marc Kruse John Lundvall Department of Agronomy Iowa State University
Soil Nitrogen and Carbon Management Project 43 Sites 2001-2003
Project Objectives Demotrate potential of a new soil N test in Iowa corn production Demotrate corn N fertilization needs in corn following soybean Demotrate impact of N fertilization on short-term soil N - C change and CO 2 release
2001-2003 Project Methods 43 Sites on Producer Fields Across Iowa Corn-Soybean Rotation, with First-Year of N Rate Application 0 to 200 lb N/acre in 40 lb N Increments Determine Economic Optimum N Rate, N Fertilizer Respoe, Relative Yield Monitor Corn N Status Leaf Greenness Multiple Soil Sampling by Depth and Time Determine Soil N, C, and Illinois N Soil Test Monitor CO 2 Emission Across Multiple Seaso
Many Procedures Evaluated for Assessing Plant-Available N Indirect (crop rotation) Plant vegetation Yield, total N uptake, uptake with no applied N, concentration, plant seing Total soil N analysis Inorganic N forms Laboratory microbial incubation Chemical extraction Water, strong acids or bases, neutral salts Analyze extract for C, total N, distillable NH 3, ultraviolet adsorption
Hydrolyzable Amino Sugar-N Basis for Illinois Soil N Test Mason-jar diffusion of amino sugar-n fraction of soil {Mulvaney and Khan, SSAJ 65:1284-1292} {Mulvaney et al., SSAJ 65:1164-1172} Improved determination of amino sugar-n fraction Indicated Pool of readily mineralizable organic-n Indicated corn respoiveness to N fertilization Critical level 200 250 ppm (12-inch depth) Potential for preplant soil sampling
Illinois Soil N Test Procedure Khan, Mulvaney and Hoeft (2001) Weigh a 1-g sample of air dried soil (ground < 2 mm) into a Mason jar Add 10 ml 2 M NaOH and swirl gently Seal jar with lid assembly containing petri dish with 5 ml boric acid-indicator solution Heat on hot-plate for 5-hr at 48-50 C Titrate boric acid solution to endpoint with standardized 0.01 M H 2 SO 4 Critical level 225-235 ppm (12-inch depth)
Soil Test Results Same for Fall and Spring Samples 0-6 and 0-12 Inch Depth Fall versus Spring Soil Sampling Illinois N Soil Test Values Fall (ppm) 600 500 400 300 200 100 0-12 Inch, 2001 0-12 Inch, 2002 0-6 Inch, 2001 0-6 Inch, 2002 0-12 Inch, 2003 0-6 Inch, 2003 0 0 100 200 300 400 500 600 Spring (ppm)
Soil Test Results Not Related to N Respoe N-Fertilizer Respoe (%) 100 90 80 70 60 50 40 30 20 10 Relatiohip Between the Illinois N Soil Test (Spring 0-12 Inch Depth Samples) and Corn N Respoe 2001 2002 2003 0 0 100 200 300 400 500 600 Illinois N Soil Test (ppm)
Soil Test Results Not Related to Relative Yield Relatiohip Between the Illinois N Soil Test (Spring 0-12 Inch Depth Samples) and Relative Corn Yield Relative Corn Yield (No N Control) 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 2001 2002 2003 0 100 200 300 400 500 600 Illinois N Soil Test (ppm)
Soil Test Results Not Related to Needed N Rate Economic N Rate (lb N/acre) 200 180 160 140 120 100 80 60 40 20 Relatiohip Between the Illinois N Soil Test (Spring 0-12 Inch Depth Samples) and Economic N Rate (10:1 Corn:N ratio) 2001 2002 2003 0 0 100 200 300 400 500 600 Illinois N Soil Test (ppm)
Soil Test Results Related to Total Soil N Illinois N Soil Test and Total Soil N (Spring or Fall 0-12 Inch Depth Samples) Total Soil N (ppm) 4000 3000 2000 1000 2001 2002 2003 Total Soil N = -41.4 + 6.608*INST, R 2 = 0.86*** 0 0 100 200 300 400 500 600 Illinois N Soil Test (ppm)
No-N (Control) Corn Yield Reflected N Respoe 100 Relatiohip Between Control (No-N) Corn Yield and Yield Respoe to Economic Optimum N 43 S-C sites N Fertilizer Respoe, % 80 60 40 20 0 53 112 118 128 137 140 148 150 158 164 168 Control (no-n) Yield, bu/acre 174 177 182 221
High Productivity Did Not Require High N Input Economic N Rate, lb N/acre 200 180 160 140 120 100 80 60 40 20 0 70 Economic Optimum N Rate (10:1 Corn:N Price Ratio) Ranked by Site Maximum Fertilized Yield 165 168 170 174 177 179 182 191 197 Maximum Yield, bu/acre 203 212 217 221 242
Economic Optimum N Rate Varied Between Season Economic Optimum N Rate at Repeat Sites Year Site 2001 2003 Difference --------lb N/acre -------- Boone-S 103 136 33 Louisa 73 117 44 Tama 38 101 63 Floyd 3 0 3 Economic optimum N rate calculated at 10:1 corn:n price ratio.
Corn Leaf Greenness Indicated N Need Relative R1 Stage Ear Leaf Chlorophyll Meter Reading vs. Applied N Rate Difference from Economic N Respoe Relative Chlorophyll Meter Reading 1.00 0.90 0.80 0.70 0.60 0.50-200 -160-120 -80-40 0 40 80 120 160 200 Difference in Average N Rate, lb N/acre 2002 N/C Sites 2001 N/C Sites 1999-2002 LTN Sites 2003 N/C Sites
Corn Leaf Greenness Similar at V15 and R1 Relative Leaf Chlorophyll Meter Reading vs. Applied N Rate Difference from Economic N Respoe Relative Chlorophyll Meter Reading 1.00 0.90 0.80 0.70 0.60 0.50-200 -160-120 -80-40 0 40 80 120 160 200 Difference in Average N Rate, lb N/acre C-S_V8 C-S_V15 C-S_R1 C-S_R3
Carbon Dioxide Emission Rate Not Affected by Prior N App., Boone-S Site 2002 Soybean Crop 300 2002 0 lbs / A Average CO2 Emission Rate (lbs / A /day) 250 200 150 100 50 80 lbs / A 160 lbs / A 200 lbs / A 0 0 20 40 60 80 100 120 140 160 180 200 Days After Planting
Carbon Dioxide Emission Rate Higher With No Applied N, Boone-S Site 2003 Corn Crop 300 2003 0 lbs / A Average CO2 Emission Rate (lbs / A / day) 250 200 150 100 50 0.61 s 0.44 s 0.33 s 0.44 s 80 lbs / A 160 lbs / A 200 lbs / A 0 0 20 40 60 80 100 120 140 160 180 200 Days After Planting
Cumulative Carbon Dioxide Emission Not Affected by Prior N App., Boone-S Site 2002 Soybean Cumulative CO2 Emissio (lbs / A) 14000 12000 10000 8000 6000 4000 0 lbs / A 80 lbs / A 160 lbs / A 200 lbs / A 2002 2000 0 0 20 40 60 80 100 120 140 160 180 200 Days After Planting
Cumulative Carbon Dioxide Emission Not Affected by N Rate, Boone-S Site 2003 Corn Cumulative CO2 Emissio Rate (lbs / A) 14000 12000 10000 8000 6000 4000 2000 0 2003 0 lbs / A 80 lbs / A 160 lbs / A 200 lbs / A 0 20 40 60 80 100 120 140 160 180 200 Days After Planting
Soybean Residue C and N Input to Soil Boone-S Site Fall 2002 N rate Dry Matter Total C Total N C:N Ratio - - - - - - - - - - - - - - - - - lb/acre - - - - - - - - - - - - - - - - - - 0 6267 a 2697 a 69 a 39 : 1 80 6025 a 2608 a 69 a 38 : 1 160 6590 a 2822 a 82 a 34 : 1 200 7385 a 3179 a 90 a 35 : 1 *Mea with the same letters are not significantly different at Pr 0.05.
Summary Illinois N Soil Test was not predictive of corn respoe to applied N or economic optimum N rate, and is not recommended for adjusting corn N fertilization on Iowa soils Corn respoe to applied N varied across sites Economic optimum N rate was not coistent between years at repeat sites
Summary Corn yield with no applied N (control) generally reflected site respoiveness to applied N Leaf greenness indicated corn N need Large amounts of CO 2 were released and approximated residue carbon input
Thank you to the many cooperators and individuals who helped make the project a success.