SOIL FERTILITY AND NUTRIENT MANAGEMENT

Transcription

1 SOIL FERTILITY AND NUTRIENT MANAGEMENT Cmpetency Areas Cmpetency Area 1: Basic Cncepts f Plant Nutritin... 2 Cmpetency Area 2: Basic Cncepts f Sil Fertility... 3 Cmpetency Area 3: Sil Testing and Plant Tissue Analysis... 8 Cmpetency Area 4: Nutrient Surces, Analyses, Applicatin Methds Cmpetency Area 5: Sil ph and Liming Cmpetency Area 6: Nutrient Management Planning Authrs/Instructrs fr Sil Fertility and Nutrient Management Quirine Ketterings, Prfessr, Nutrient Management Spear Prgram, Department f Animal Science, Crnell University. Karl Czymmek, Senir Extensin Assciate, PRO-DAIRY Prgram, Department f Animal Science, Crnell University. Dug Beegle, Prfessr, Department f Plant Sciences, Penn State University. Je Lawrence, Dairy Frage Systems Specialist, PRO-DAIRY Prgram, Department f Animal Science, Crnell University. With thanks t ur past cntributrs: Tm Bub, Extensin Educatr, University f New Hampshire Cperative Extensin. Patty Ristw, Extensin Assciate, Nutrient Management Spear Prgram, Department f Animal Science, Crnell University. Lead Editrs: Nicle Smaranda, NRCCA Intern, and Quirine Ketterings, NRCCA C-Chair. Last Updated

2 Cmpetency Area 1: Basic Cncepts f Plant Nutritin 1. List the 17 elements essential fr plant nutritin. Nutrient Macr/micr Uptake frm Mbility in Plant 1 Carbn Macr CO2,H2CO3 2 Hydrgen Macr H +,OH -,H2O 3 Oxygen Macr O2 4 Nitrgen Macr NO3 -,NH4 + Mbile 5 Phsphrus Macr HPO4-2,H2PO4 - Smewhat Mbile 6 Ptassium Macr K + Mbile (very) 7 Calcium Macr Ca +2 Immbile 8 Magnesium Macr Mg +2 Smewhat mbile 9 Sulfur Macr SO4 - Mbile 1 Brn Micr H3BO3,BO3 - Immbile 11 Cpper Micr Cu +2 Immbile 12 Irn Micr Fe +2,Fe +3 Immbile 13 Manganese Micr Mn +2 Immbile 14 Zinc Micr Zn +2 Immbile 15 Mlybdenum Micr MO4 - Immbile 16 Chlrine Micr Cl - Mbile 17 Nickel Micr Ni +2 Mbile 2. Classify each essential elements as macrnutrient r micrnutrient. See Table 1. The macrnutrients can als be gruped as primary nutrients (nitrgen, phsphrus and ptassium) and the secndary nutrients (calcium, magnesium and sulfur). This grup f nutrients is used in large quantities. The micrnutrients are used in much smaller quantities but equally essential. 3. Recgnize the functins f N, P, and K in plants. Nitrgen: fund in chlrphyll, nucleic acids and amin acids; cmpnent f prtein and enzymes. Phsphrus: an essential cmpnent f DNA, RNA and phsphlipids which play critical rles in cell membranes; als plays a majr rle in the energy system (ATP) f plants. Ptassium: plays a majr rle in plant metablism, and is invlved in phtsynthesis, drught tlerance, imprved winter-hardiness and prtein synthesis. 4. Distinguish each macrnutrient as mbile r immbile in the plant. See Table 1. In shrtage cnditins, nutrients that are mbile in the plant will mve t new grwth areas s deficiency symptms will first shw up in the lder leaves. Nutrients that are immbile in the plant will nt mve t the new grwth s deficiency symptms shw up in the new grwth. 2

3 5. List chemical uptake frms fr each macrnutrient. See Table 1. Take nte: sme f the nutrients are taken up in mre than ne frm. 6. Describe hw nutrient demands change at different plant grwth stages. In general, nutrient needs increase as the plant grws thrugh the seedling stage int the reprductive stage (silking and tasseling). Fr nitrgen, the rate f uptake increases rapidly between V8 (knee high typically) and R1 (silking). When plants are yung and small, nutrient need is lw. As plants enlarge and start t grw rapidly, nutrient needs increase dramatically. Cmpetency Area 2: Basic Cncepts f Sil Fertility 7. Recgnize the rle f the fllwing in supplying nutrients frm the sil: A. Sil slutin D. Sil minerals B. Catin exchange sites E. Plant residue C. Organic matter The sil slutin is the liquid in the sil and plant nutrients disslved in the sil slutin can mve int the plant as the water is taken up. Catins (psitively charged ins such as calcium, magnesium and ptassium) are held n negatively charged exchange sites in the sil. Catin exchange capacity (CEC) is a measure f the amunt f catins that can be held by the sil and released int the sil slutin. Sils with a greater catin exchange capacity (see PO#1) are able t hld nt mre nutrients. Organic matter cntains nutrients that are released fr plant uptake thrugh micrbial decmpsitin. As sil minerals (clays, carbnates, etc.) weather (breakdwn) they release nutrients fr plant uptake. A gd example f this is ptassium. As plant residues breakdwn, the nutrients in them becme available t grwing plants. Nitrgen is typically the ne we think f, but the ther essential nutrients in plant residues will becme available fr plant uptake as well. The speed and degree f the breakdwn f residues will depend n envirnmental factrs such as misture and temperature. Mst nutrients are released as the rganic mlecules in the residue are brken dwn by micrbes. Hwever, sme nutrients, like K, are nt part f any rganic mlecules in residues and thus are released much mre rapidly. 8. Describe the fllwing nutrient transfrmatins and interactins: A. Mineralizatin C. Nutrient uptake antagnism B. Immbilizatin Mineralizatin refers t the cnversin f rganic N surces (plant residues, manures, and bislids) t inrganic N surces. This is accmplished by a wide variety f micrrganisms. Immbilizatin is the reverse f mineralizatin as this refers t the cnversin f inrganic frms f nitrgen int rganic frms, such as micrbial cells and rganic matter. 3

4 Mineralizatin and Immbilizatin ccur at the same time. The net effect f these tw prcesses is typically determined by the rati f carbn t the nitrgen cntent in the rganic material. Fr example, a C:N rati less than ~2 typically results in net mineralizatin f N and a C:N rati greater than ~3 typically results in net immbilizatin f N. Nutrient uptake antagnism refers t circumstances where, depending n sil cnditins and nutrient frm and availability, plant uptake is weighted favrably tward sme nutrient(s) ver thers. 9. Describe hw the prcesses f mass flw, diffusin, and rt interceptin affect nutrient uptake. Mass flw f a nutrient ccurs when it is disslved in the sil slutin and flws with water int the plant. This is the majr prcess fr uptake f nitrgen, calcium and magnesium. Diffusin is the mvement f a nutrient frm an area f high cncentratin t ne f lwer cncentratin. Typically the nutrient will mve frm the sil slutin (high cncentratin) t the rt surface (lw cncentratin). This is an imprtant prcess fr phsphrus and ptassium and is a key thery behind the use f banded r starter fertilizer. Rt interceptin ccurs when a rt grws in t a fresh area r surface f clay r rganic matter reducing the distance a nutrient must diffuse and thus increasing absrptin f the nutrient. Rt interceptin is extremely imprtant fr very immbile nutrients like P and thus having gd sil cnditins fr rt grwth is essential fr gd P nutritin. 1. Describe hw catin exchange capacity (CEC) influences nutrient mbility and uptake. Catin exchange capacity (CEC) is a measure f the amunt f catins (psitively charged ins) that can be held by the sil. As the clay cntent, rganic matter cntent and ph increase, the CEC will als increase. As CEC increases, s des the ability f the sil t hld nutrients. Since much f the plant uptake (and leaching) f nutrients cmes frm the sil slutin, as the CEC increases, the nutrients in slutin decrease and becme less mbile in the sil. Having ptimum levels f catins n the CEC and having lw levels f nn-nutrient and ptentially harmful catins such as Al n the CEC is imprtant fr supplying these essential nutrient catins fr plant uptake. 11. Distinguish each macrnutrient as mbile r immbile in the sil and recgnize difference in mbility depending n frm. The mbility f nitrgen is dependent n the frm it is in. If it is in the nitrate frm (NO3 - ) it is very mbile with the sil water and can be easily leached. In the ammnium frm (NH4 + ) it can be held n catin exchange sites and is nt susceptible t leaching. Phsphrus is typically immbile in the sil unless sil test levels rise abve the sil s ability t bind it. Calcium, magnesium and ptassium are cnsidered immbile in sil since they are held n catin exchange sites. Sulfur (as sulfate SO4 - is an anin and nt held n catin exchange sites) is mbile in mst sils. 12. Describe hw the fllwing sil characteristics affect nutrient uptake: A. Texture D. Misture B. Structure E. ph C. Drainage/aeratin F. Temperature 4

5 Texture is defined as the prprtin f sand, silt and clay in the sil. As the clay cntent increases, s des the CEC, resulting in a greater ability t hld nutrients. Sils with mre sand and less clay have lwer CECs and cannt hld as many catins. Since sandy sils als have large pre spaces, leaching f nutrients is greater than n a sil with mre silt and clay. Sil structure is defined as the arrangement f sil particles int aggregates. Gd sil structure is represented by significant aggregatin. This allws fr ptimal rt grwth and water and nutrient access fr any given sil. Destructin f gd structure, by cmpactin r tillage can result in an increase in runff since water cannt mve as readily dwn thrugh the sil prfile. Under pr drainage cnditins, nitrate nitrgen can be lst thrugh denitrificatin. With excessively drained sils (sandy) leaching lsses are mre imprtant. Sme nutrients like irn and manganese are mre sluble under very wet r flded cnditins. Sil misture is very imprtant fr rt grwth, s adequate misture will imprve uptake f nutrients by diffusin and rt interactin. Sil misture is als imprtant fr rganic matter decmpsitin (which releases N, P and S). Sil ph affects the availability f mst nutrients. Fr example, at lw ph and high ph, phsphrus is less available than when the ph is arund 6.5. At a lw ph it is bund by aluminum and irn and at a high ph is bund by calcium. Many f the micrnutrients are als sensitive t ph, being mre available in slightly acid sils. At high ph s, mlybdenum can becme t available and be txic t plants. See #43 fr mre detailed infrmatin. Sil ph is imprtant in N transfrmatins including mineralizatin f rganic materials (bilgical degradatin), nitrificatin (bacteria respnsible fr this prcess are ph sensitive) and N fixatin. Temperature affects the plant s ability t grw and thus affects nutrient uptake. Temperature als cntrls the mineralizatin f rganic frms f nutrients t mineral frms that plants can take up. Mineralizatin and thus nutrient availability is reduced r stpped cmpletely at very lw and very high sil temperatures. 13. Describe hw the fllwing affect the fate f N in sil: A. Fixatin by clay F. Immbilizatin B. Ammnificatin/mineralizatin G. Leaching C. Nitrificatin H. Plant uptake D. Vlatilizatin I. Symbitic fixatin E. Denitrificatin A. Since the sil has a negative charge, the ammnium in (NH4 + ) can be bund t sil particles. Depending n the type f clay, this in can be trapped in the actual structure f the clay mineral and becme unavailable fr plant uptake as well. B. Ammnificatin/Mineralizatin (see diagram belw) is the cnversin f rganic nitrgen t ammnium-n by micrbes as they decmpse the rganic matter. If large amunts f N-rich rganic materials with narrw C:N ratis (<2) is added, significant levels f ammnium can be prduced. This will then be cnverted t nitrate (nitrificatin), absrbed by plants, fixed r held by the sil r cnverted t ammnia and lst t the air (vlatilizatin). Mineralizatin readily ccurs in warm (68-95 F), well-aerated and mist sils. As a rugh estimate, abut 6 8 lbs f N/acre is mineralized n average frm sil rganic matter each year in the Nrtheast. Actual mineralizatin rates can vary greatly depending n rganic matter cntent f the sil, sil bilgical activity, and weather cnditins. 5

6 R-NH 2 NH 3 NH + 4 rganic N ammnia ammnium R reflects the (undefined) rest f the mlecule. Ammnificatin/Mineralizatin C. Nitrificatin (see diagram belw) is a tw-step prcess that cnverts ammnium t nitrite (by ne species f bacteria) and then t nitrate (by a secnd species f bacteria). These bacteria are sensitive t temperature, misture and sil ph. Nitrificatin is mst rapid when sil is warm (67-86 F), mist and well-aerated, but virtually ceases belw 41 F and abve 122 F. Nitrsmmas Nitrbacter NH + 4 NO - 2 NO - 3 ammnium nitrite nitrate Nitrificatin D. Vlatilizatin (see diagram belw) is the lss f ammnium N thrugh cnversin t ammnia. Vlatilizatin lsses are higher fr manures and urea fertilizers that are surface applied and nt incrprated (by tillage r by rain) int the sil. Manure cntains N in tw primary frms: ammnium and rganic N. If manure is incrprated within ne day, apprximately 65% f the ammnium N is expected t be retained; when incrprated after 5 days the ammnium N will have been lst thrugh vlatilizatin. Organic N in manure is nt lst thrugh vlatilizatin, but it takes time t mineralize befre it becmes plant available. H 2N-C-NH 2 NH 4 + NH 3 Urea ammnium ammnia Vlatilizatin E. Once nitrgen in the sil is in the nitrate (NO3 - ) frm, several things can happen. Under waterlgged r flded (anaerbic) cnditins, nitrate can be cnverted t gaseus frms f N. Under typical cnditins the majrity wuld be in as N2 gas. Hwever, a significant amunt f N released in this prcess is in the frm f nitrus xide, a very ptent greenhuse gas. This prcess is called denitrificatin (see diagram belw). NO - 3 NO - 2 NO N 2O N 2 nitrate nitrite nitric nitrus nitrgen xide xide gas Denitrificatin F. If the sils are nt wet (aerbic), the nitrate can be used by micrbes t breakdwn mre rganic materials. Immbilizatin refers t the prcess where nitrate and ammnium are taken up by sil rganisms and therefre becme unavailable t crps. Incrpratin f materials with a high carbn t nitrgen rati (e.g. sawdust, straw, etc., with C:N>3), will increase bilgical activity and cause a greater demand fr N, and thus result in N immbilizatin (see diagram belw). Immbilizatin nly temprarily lcks up N. When the micrrganisms die, the rganic N cntained in their cells is cnverted by mineralizatin and nitrificatin t plant available nitrate. NH 4 + and/r NO 3 - R-NH 2 ammnium nitrate rganic N R reflects the (undefined) rest f the rganic mlecule. Immbilizatin 6

7 G. If sufficient rain ccurs nitrate can be lst t grundwater by leaching thrugh the sil prfile belw the rts f the plants. H. If cnditins are aerbic (nt wet r flded) nitrate can be taken up by the plants. I. Symbitic fixatin f nitrgen is a mutually beneficial prcess between a legume plant and the assciated micrrganism (Rhizbium sp.). The plant prvides the micrbe with an energy surce t cnvert N2 frm the atmsphere t ammnium that can be utilized by the plant. Nitrgen fixatin requires rhizbia, energy, enzymes and minerals. If a plant available frm f N is present, the crp will use it instead f fixing N frm the air. N 2 NH 3 R-NH 2 nitrgen gas ammnia rganic N R reflects the (undefined) rest f the rganic mlecule. N fixatin The Nitrgen Cycle See als: 7

8 14. Describe hw the fllwing sil factrs affect symbitic nitrgen fixatin: A. ph D. Nitrgen level B. Misture E. Aeratin C. Ppulatin f crrect Rhizbia species F. Organic matter The micrbes that are respnsible fr symbitic nitrgen fixatin are very sensitive t ph. As the ph drps, fixatin will slw. Very little will ccur belw a ph f 5.. The Rhizbia species that are respnsible fr fixatin perate under gd misture cnditins. If it gets t wet r dry micrbial activity will slw dwn. Under drught cnditins, fixatin will stp. There are numerus species f Rhizbium, and they each require a specific hst. The inculatin f the legume seed with the crrect species (especially the first time this legume has been in the field) is extremely imprtant t btaining gd levels f fixatin. Fr example, the symbitic bacteria fr sybean will nt fix nitrgen with alfalfa. As readily available nitrgen frm ther surces (fertilizers, manures, bislids, rganic matter) increases, the amunt f nitrgen fixed decreases. Since the Rhizbia are aerbic bacteria, aeratin is very imprtant. Under very wet cnditins they will nt fix as much nitrgen. Under wet cnditins, leaching and denitrificatin lsses may increase as well. If the rganic matter cntent is very high, and the supply f available nitrgen is plentiful, the bacteria will nt fix as much nitrgen. 15. Recgnize hw different crps and crpping systems affect sil fertility and fertilizatin strategies based n the prcesses utlined in Cmpetency Area 6 in Crp Management Fertility management in ne year will impact fertility status the next year. Thus, recmmendatin systems shuld take int accunt crp rtatins. One example is crn in rtatin with hay (alfalfa, alfalfa-grass r grass). First year crn after hay des nt need any additinal N, aside frm ptentially 2-3 lbs N/acre f starter fertilizer, as it benefits frm the significant pl f N mineralized frm the rts and remaining abve grund bimass f the hay present befre rtatin t crn. Als crn after sybeans needs less external N (typically 2-3 lbs N/acre less) as it benefits frm the sybean in the rtatin. Similarly, when manure is applied t meet N needs f a crp like crn, P and K are typically applied in excess f crp remval, typically eliminating the need fr additinal P and K fr the crp that fllws the crn. Often times in wheat and crn rtatins, farmers manage fertility fr the crn, while the wheat benefits frm nutrients nt taken up by the crn. Cmpetency Area 3: Sil Testing and Plant Tissue Analysis 16. Recgnize hw the fllwing affect sil sampling methds: A. Methd f previus fertilizer applicatin B. Tillage system C. Nutrient stratificatin D. Within-field sil and crp variability 8

9 A. Banding f fertilizer applicatins and manure spreading are knwn t increase spatial variability within a field. Nt every inch f surface area receives the same amunt f fertilizer and/r manure and the mre variability in the field, the mre sub-samples shuld be taken. Avid sampling in any fertilizer bands where pssible. B. Tillage can impact distributin f nutrients ver a field and ver depth (deep tillage, zne till, etc.). This can impact sampling density as fewer samples per unit area are needed fr less variable fields. Hwever, fr practical implicatins, a reductin in sampling density is nt recmmended unless intense (grid) sampling shws that a similar reliability can be btained at a lwer sampling density. C. In n-till systems, nutrient stratificatin is usually greater than fr cnventinally tilled fields. Cnsistent sampling t the recmmended depth is critical in n-till systems. Fr sil ph in n-till systems, tw sil samples will be needed, ne representing -1 inch (fr seeding) and anther fr 1-6 inches depth. If the surface sample (-1 inch) ph is belw 6. a limestne applicatin shuld be made even if the deeper sample des nt call fr liming. D. Fr the best sampling prtcl, take 2-3 subsamples per acre and cmbine int a cmpsite sample. One cmpsite sample shuld nt represent mre than 1 acres (unless past sampling shws minimal differences). Als the area t be sampled shuld be relatively unifrm, i.e. similar sil prperties and past management. If there are knwn significant differences within the area t be sampled e.g. ld fence rws, manure r lime stckpile areas, wet spts, etc., a mdified sampling strategy shuld be fllwed. If the areas are t small t manage separately, avid taking any subsamples frm these areas. If they are large enugh fr the farmer t practically manage them separately, take a separate sample frm these areas. 17. Indicate hw the fllwing may cause variability in sil test results: A. Time f sampling E. Type f extractin methd used B. Depth f sampling (Mrgan, Mdified Mrgan, C. Number f samples taken Mehlich-3, Bray, Olsn) D. Sample handling Nutrient cntent f the sil slutin and sil matrix vary depending n the time f year. T minimize variability and build the strngest histric recrds take samples in the same time f the year. Take samples ver a cnstant depth t minimize additinal variability and build the strngest histric recrds. Depth f sil samples depends n tillage used n the field. Samples are nrmally taken frm the surface t the tillage depth (usually 6-8 inches deep). This depth is imprtant because lime and fertilizer are mixed within the tilled layer. Fr lime recmmendatins fr n-till r minimum-till crps, take a sample frm the -1 inch depth and ne frm -6 inches. The tw samples shuld be placed in separate plastic bags labeled clearly with -1 inch and -6 inch. Fr the best sampling prtcl, ne sample shuld nt represent mre than 1 acres. One sample shuld represent ne management unit (cnsider sil type and past management). Test at least nce in 3 years r twice in a rtatin. Use the right sampling tl: prbe r auger and a clean plastic bucket. Take 2-3 subsamples per acre acrss a unifrm field. Mix subsamples and take a 1 cup subsample. Label the sample and keep a recrd f the sample and its lcatin. Avid sampling when the sil is very wet. Scrape away surface litter befre inserting the sil prbe. Take equal amunts fr each subsample. Take cres t plw depth (n-till: inches, cnventinal tillage -8 inches). Sample between crp rws, avid fence rws. Remve stnes, wd, trash and ther debris. 9

10 Have samples analyzed by a lab that uses sil testing extractin methds that are apprpriate and recmmended fr the area. Histrical recrds help managers and agrnmists track changes ver time. Fr the best cmparisns, have the analyses dne by the same labratry (same extractin methd) each time yu sil test. Cnversin equatins between different extractin methds and labratries are nt 1% crrelated and errrs are intrduced when cnversin equatins are used. Furthermre results frm ne labratry cannt be cmbined with anther t create a histrical recrd. 18. Cmpare and cntrast the fllwing appraches fr making fertilizer recmmendatins: A. Sufficiency level C. Catin saturatin ratis B. Sil buildup and maintenance A. Sufficiency level: Methd used by mst land grant universities. In this apprach, the fertilizer rate is based n expected crp respnse (increased yield) based n the limiting factr cncept. The agrnmic sil test is an index that can be used, based n a large amunt f lcal field studies, t determine (1) if a respnse t extra fertilizer is t be expected and if s, (2) hw much f that fertilizer needs t be added. Field calibratins are needed t develp a recmmendatin system. In the diagram belw the arrws indicate the fertilizer recmmendatin fr each f the three different sil test levels in this example based n the calibratin data. B. The Sil buildup and maintenance apprach is based n building the sil test level t the ptimum range, and then maintaining it in the ptimum range. In the ptimum range, there is a lw prbability f an additinal respnse t adding fertilize. The buildup part f the recmmendatin is determined by the expected crp respnse t the added nutrients similar t the sufficiency level apprach. The maintenance part f the recmmendatin is based n replacing the amunt f nutrient expected t be remved by the crp. This shuld keep the sil test level frm becming belw ptimum between sil tests. When the sil test reaches a level where crp remval will nt reduce the sil test t belw ptimum, n additinal nutrients are recmmended. The crp is allwed t draw the nutrient levels dwn int the ptimum range. C. The catin saturatin rati apprach guides management f Ca, Mg and K and suggests benefits f farming at an ideal rati f Ca, Mg, and K n the CEC. The mst cmmnly applied rati is: 65% Ca, 1% Mg, 5% K, 2% miscellaneus. Hwever, studies by e.g. Liebhart (1981), McLean (1977) and McLean and Carbnell (1972) suggest n relatinship between %K and Mg saturatin and yield. Especially fr calcareus sils, adjustments t particular ratis can be very expensive and saturatin estimates based n summatin f catins can be inaccurate. Generally, if the sil ph and the sil test K 1

11 and Mg levels are ptimum, the balance f catins n the CEC will supprt ptimum crp prductin and further adjustments in catin saturatin n the CEC are nt beneficial. Ca ++ Mg ++ Sil slutin H + K + NH4 + Ca ++ Mg ++ K + NH4 + Fe ++ Al +++ Fe ++ Mn ++ H + Mn ++ Liebhardt, W.C Sil Science Sciety f America Jurnal 45: McLean, E.O ASA Special Publicatin n. 9. McLean, E.O., and M.D. Carbnell SSSA Prceedings 36: Recgnize hw the fllwing affect sil test interpretatin: A. Prbability f crp respnse t added E. Results reprted as elemental nutrients versus xide frms (cnversin B. Estimate f nutrient sufficiency level factrs) C. Results reprted as ppm r lbs/acre F. Envirnmental risk D. Within-field variability G. Extractin methd It is imprtant t recgnize that an agrnmic sil test = INDEX f nutrient availability. Lcal field research is needed t calibrate an agrnmic sil test fr its ability t (1) identify the likelihd f a respnse t additinal nutrients, and (2) accurately predict the amunt f nutrient needed t reach sufficiency levels. This research needs t be cnducted under lcal cnditins t be applicable s fertility recmmendatins are state-specific and smetimes even regin specific. The agrnmic critical sil test level is defined as the sil test level beynd which a respnse t additinal fertilizer is unlikely. Keep in mind, sil testing fr fertility management requires lcally applicable crp respnse studies that link sil test levels t prbability f a crp respnse and actual nutrient needs. Risk f envirnmental lss increases with 11

12 increase in sil test beynd the critical sil test value. Within-field variability needs t be taken int accunt in sil sampling prtcls (see PO#2). As a first requirement, a gd sil testing labratry needs t have a gd quality cntrl system in place. Hwever, high quality labratries can give different results if individual samples are split and sent t different labratries. This is because sil testing labratries can differ in: 1) Nature f the extract used (e.g. Mrgen, mdified Mrgan, Mehlich-3, Bray-1). 2) Shaking time. 3) Slutin t sil rati. 4) Analytical prcedure/instruments used. 5) Way f reprting results (ppm r lbs/acre, P r P2O5, K r K2O): 1 ppm = 2 lbs/acre (`7 inches deep) 1 lb P/acre = 2.3 lbs P2O5/acre; 1 lb K/acre = 1.2 lbs K2O/acre Mst cmmn extractin methds used in the Nrtheast include Mrgan (sdium acetate), mdified Mrgan (ammnium acetate), Mehlich-3, and fr P als Bray-1 and Olsen. These varius methdlgies were develped fr specific purpses (Bray fr lw ph sils, Olsen fr calcareus sils, etc.).the recmmended test fr an area shuld always be used. Results frm ne methd can nly be equated t thse frm anther methd (r labratry) if reliable cnversin equatins exist. Even then, cnverted results are nt as gd as using the recmmended test t begin with. 2. Describe sil sampling strategies and knw their applicatin: A. Randm sampling B. Grid-based C. Sil type based sampling D. EC r yield map based Sil type and management impacts sil nutrient levels and crp prductin. Fr mst accurate results, take 2-3 samples per acre in a randm pattern that cvers the field and limit field size t n mre than 1 acres t reduce the risk f sampling multiple sil types within a field. See PO#16 abve fr mre n sampling methds. Grid sampling will be helpful if there is large within-field variability, if that variability is within the respnsive range fr nutrients and ph, and if the farmer has the ability t manage based n this variability. In grid sampling a field is 12

13 divided int small (usually 1-4 acres) blcks (grid cells) and a separate sil sample is taken frm each f these grid cells. The sample may be 6-1 subsamples taken frm a small area at the center f the grid cell r it may be 6-1 subsamples taken randmly (see abve) frm thrughut the grid cell. Sample results are cmpiled either directly int a map shwing the different sil test levels and recmmendatins fr each grid cell r the test results may be statistically smthed t create a map (see figure n the right). It is imprtant that apprpriate statistical methds are used t create these maps. In recent years, sil sampling based n electrical cnductivity mapping r yield mapping has increased in ppularity. These appraches bth divide fields in znes (typically 2-4 znes) which are then assessed fr sil fertility. Such sampling can be mre targeted and less time-cnsuming than grid sampling. Further research is needed t develp management guidelines based n EC r yield znes in the Nrtheast. 21. Recgnize factrs that influence the results f the pre-sidedress nitrgen test: A. Timing f sampling relative t C. Field variability weather patterns D. Sample prcessing B. Depth f sampling The Pre-Sidedress Nitrate Test (PSNT) is an in- seasn sil nitrate test that can be used t determine if additinal fertilizer nitrgen (N) is needed fr crn. This test is taken at sidedressing time just befre the perid f majr N demand by crn. It is mst useful fr fields with a histry f manure and/r sd incrpratin. The PSNT is nt a direct measure f available N, but is designed t: 1) estimate the sil s nitrate supplying ptential, and 2) decide if that is enugh N t meet crp needs. The PSNT is particularly useful when it is unclear whether enugh manure was actually applied. Over the curse f a few years, carefully cmpare PSNT results with fertilizer and manure inputs and crp perfrmance. When t use: In crn fields, 2 nd year r mre after a sd and/r where the manure rate is uncertain. If nt enugh manure was applied t meet the expected N needs f the crp. Where nt t use the PSNT: The test is useless fr crn fields that received pre-plant r early pst-plant bradcast fertilizer N applicatins (ther than <4 lbs starter N/acre). Any leftver nitrate frm bradcast fertilizer will be picked up by the PSNT, resulting in an verestimatin f the true rganic N supply. First year crn after a grass and/r alfalfa des nt need additinal N beynd a small starter N applicatin (2-3 lbs N/acre). S, it is a waste f time and mney t sidedress N fr first year crn therefre it is nt necessary t take a PSNT. In additin, PSNT results f first year crn fields tend t underestimate actual N supply making them less reliable as indicatrs. Hw t take samples? Limit sampling t areas f 1 acres r less and take a separate sample fr areas with different crn stands (different ppulatin densities, stage f develpment, and/r clr, crp histries, fertility management, significant changes in slpe, etc.). Sample between crn rws t a depth f 12 inches (stay away frm the starter band). Sample when the crn is 6-12 inches tall. D nt sample t clse t a rain event that culd have resulted in nitrate leaching (wait fr 2-3 days after significant rainfall). Samples shuld be dried immediately (spread the sample thinly and dry in the sun r under a fan) t stp N mineralizatin and sent t the labratry. 13

14 Interpretatins can be state-specific. The PSNT guidelines fr New Yrk are: PSNT ppm Likeliness f an ecnmic respnse t N guideline nitrate-n extra N 25 Lw N additinal N needed Abut 1% If uncertain, cnsider sidedressing 25-5 lbs N/acre <21 High Apply sidedress N accrding t the Crnell N guidelines fr crn* *The N guidelines fr crn as well as the NYS Crn N Calculatr can be dwnladed frm the NMSP website: (nmsp.cals.crnell.edu/nutrient_guidelines). Fr fields with <21 ppm: If a PSNT sample is cllected frm a field expected t need sidedress N (fr example a field that received less manure than needed t meet N needs), add the extra N. If a PSNT sample is cllected frm a field nt expected t require sidedress N (fr example where manure applicatins shuld have supplied sufficient N), make sure the field actually received the planned manure applicatin and that the field histry is crrectly recrded. Check N needs with the NYS Crn N Calculatr. If under the lwest manure applicatin estimates, the calculatr still shws that n additinal N is needed, despite the PSNT being <21 ppm, rganic-n mineralizatin rates early in the seasn were likely lwer than average but n additinal N is needed because the field is expected t supply sufficient nitrgen frm rganic surces nce mineralizatin cnditins imprve (warm and mist sils). If the calculatr shws that additinal N is needed and the PSNT is <21 ppm, cnsider adding the extra N. 22. Describe hw t use plant tissue analysis fr: A. Prblem slving/diagnsis B. Nutrient prgram mnitring C. In-seasn nutrient management Analyzing plant tissue can indicate the success f a sil fertility prgram and uncver ptential prblems. Plant tissue analysis cmplements sil testing by measuring the nutrients actually taken up by the plant. In additin, secndary nutrients and micrnutrients that currently are nt rutinely measured in sils can be measured reliably in plants. It shuld be nted, hwever, that plant nutrient cntent represents the effects f nt nly sil nutrient status but als all the factrs cntrlling plant grwth. Therefre, a single year s infrmatin may nt be useful fr planning a sil fertility management prgram. But as results are accumulate ver a perid f years, the infrmatin will becme mre valuable. Sample cllectin is very imprtant. The nutrient cncentratin in a plant varies with the plant s age and the part f the plant sampled. If plant analyses are t be meaningful, the apprpriate plant part must be cllected fr the age f the plant, and enugh plants must be included t btain a representative sample. Specific directins n plant sampling generally are available with each sampling kit frm the plant analysis labratry. Plant tissue analyses may be useful in diagnsing crp nutritinal prblems. Take samples frm the prblem area and a nearby nrmal area fr cmparisn. Then, use all available infrmatin t interpret the plant analysis fr diagnsing a nutrient deficiency. Lk carefully at symptms n the plants, nte any patterns in the field, and cnsider the timing f the prblem s appearance. Keep in mind that nt all nutrient deficiencies in plants are the result f nutrient deficiencies in the sil. Sil testing and plant analysis can cnfirm each ther, but they als can indicate when the cause f the prblem is smething ther than a nutrient deficiency in the sil. If the sil test level is adequate but the plants are deficient, 14

15 sme ther factr is limiting the plant s ability t take up nutrients. Sme areas t cnsider include: pssible interactins with ther cultural practices such as tillage r pesticide use; pest injury such as rtwrm feeding; differences in varieties r hybrids; r sil physical cnditins such as cmpactin. Leaf symptms are nly guides t the surce f the truble - dn t use leaf symptms alne. Usually under field cnditins mre than ne deficiency symptms is present; therefre, symptms are cmplicated. Diseases may enhance nutrient deficiencies and vice-versa. Stress f any type can prduce r enhance plant symptms, i.e., the purple clring f crn in spring is brught n by cld stress, dry cnditins r cultivatr damage resulting in rt pruning can cause K deficiency. Zn deficiency is ften the result f pr rt grwth. 23. Recgnize hw the fllwing terms relate t plant nutrient level: A. Critical value D. Luxury cnsumptin B. Sufficiency range E. Txicity level C. Optimum, belw ptimum and abve ptimum sil nutrient levels The critical value (r mre ften range) f a specific nutrient is the sil r tissue cntent belw which, the plant mst likely was deficient in that specific nutrient and prductin culd have been enhanced by additin f the nutrient. Deficiency Sufficiency Txicity 15

16 Thus, belw the critical value, the nutrient levels are belw ptimum. Luxury cnsumptin ccurs when plants take up mre f a specific nutrient than needed fr ptimum functining and prductin. An example f a nutrient that can be cnsumed in excess f crp needs is ptassium. 24. Recgnize hw the fllwing affect plant tissue analysis results: A. Crp species D. Crp stress level B. Grwth stage E. Time f day sampled C. Plant part sampled F. Sample handling Plant tissue nutrient interpretatin depends n (1) species sampled, (2) plant part, and (3) time f sampling. Sampling is nt recmmended when the plant part is sil r dust cvered, mechanically injured, damaged by insects, r diseased, r under misture r temperature stress (early mrning sampling is preferred). Plants under lng perids f stress can develp unusual cncentratins which can be misleading. Samples shuld be cleaned t remve surface cntaminatin. The washing shuld be quick t avid leaching f nutrients like ptassium and calcium. Always lk up specific sampling instructins prir t sampling. Examples are: Tree fruits: Time: between 6 and 7 days after average petal fall day Part: the middle f the current seasn s terminal shts Strawberries: Time: within the first 6 weeks after harvest Part: healthy leaves, well expsed t light Alfalfa: Time: bud t 1% blm Part: leaves frm the tp 1/3 f the plant 25. Recgnize factrs that influence the results f the crn stalk nitrate test: a. Sampling prtcl b. Manure histry c. Crp rtatin d. Fertilizer rate, methd f applicatin and timing The crn stalk nitrate test (CSNT) is an end-f-seasn evaluatin f the N supply fr crn during the grwing seasn. It is useful as a management tl as it helps assess N management at the end f the grwing seasn and can identify if adjustments in N management may be useful in future years. It is recmmended fr use fr 2 nd r higher year crn after hay, cntinuus crn, r crn after sybeans. The interpretatins are: Lw (deficient) = less than 25 ppm N Marginal (pssibly deficient in challenging years) = 25 t 75 ppm N Optimal (target) = 75 t 2 ppm N Excess (mre than the crn needed) = greater than 2 ppm N Lw (deficient) Plants had difficulty accessing enugh nitrgen in the sample area. Nitrgen access was hindered by inadequate supply, rt restrictins, lack f misture, r nutrient deficiency interactins. At harvest time, leaves are dead t r abve the ear leaf and/r the entire plant has a light green clr. 16

17 Marginal In sme years, yields culd have been increased with sme additinal N. In thse years, plants lk like described as abve. In ther years, the N supply was sufficient. As it is difficult t predict what kind f grwing cnditins a seasn will bring, farmers are advised t target CSNTs in the ptimal range. Optimal (sufficient) Nitrgen availability was within the range needed fr ptimum ecnmic prductin f crn. In this range, three f the five lwer leaves will be dead by harvest time while the tp leaves remain medium t dark green. Excess If the sample has mre than 2 ppm N, the crn had access t mre N than it needed fr ptimum yield. Mst likely, fewer than three leaves frm the bttm will have died; the tp leaves remain medium t dark green. If manure and/r N fertilizer was applied, the applicatin(s) supplied mre N than the crp needed that grwing seasn. A. Sampling prtcl Timing Fr crn silage, samples culd be cllected between ¼ milk line, which is just befre silage harvest, t abut 3 weeks after black layer frmatin. Methd The prtin f the stalk used fr the test is imprtant. Tw methds can be used: (1) sample an 8-inch piece f the stalk, between 6 and 14 inches abve the grund; r (2) take a 6-inch sample between 2 and 8 inches ff the grund. If the silage cutting height in the field exceeds 14 inches, cllect the standard 8-inch sectin f stalk frm the 6-14 inch height. When stubble height is less than 14 inches but greater than 8 inches, stalk samples can be taken between 2 and 8 inches ff the grund. This alternative cutting height shuld be reprted t the labratry when submitting CSNT samples s the labratry staff can prperly adjust the result. This is needed because stalk nitrate levels are higher in the lwer prtins f the stalk; with 2-8 inch samples, labratry values need t be divided by 1.5 fr the test results t be cmparable t the New Yrk interpretatin scale f lw (<25 ppm), marginal (25-75 ppm), ptimal (75-2 ppm) and excess (>2 ppm). Leaf sheaths shuld be remved and pieces need t be handled t avid cntact with the sil, especially the stalk ends. Als, avid sampling stalks frm crn shwing significant damage frm disease r insects, such as crn brers. Split each stalk int fur parts by cutting it lengthwise using a clean kitchen knife. Discard 3 f the 4 quarters. This will quicken the drying prcess withut cmprmising n the number f plants sampled. In a unifrm field ( 15 acres in size), fifteen 8-inch segments shuld be randmly cut and cmbined t make ne sample t be submitted fr analysis. Within field variability frm stalk t stalk can be large. Sampling density shuld nt be less than ne sample per acre. Avid sampling f diseased r damaged plants, and sampling f unrepresentative areas. Targeted within field sampling culd be cnsidered, in cnjunctin with within field yield mapping and precisin applicatin (within-field) r manure and/r fertilizer. Samples shuld be submitted as sn after cllectin as pssible. Samples shuld be placed in a paper bag (nt plastic). This allws fr sme drying t ccur and minimizes grwth f mld. The CSNT levels were nt impacted by days f strage at rm temperature during 8 days fllwing sampling. Samples can be stred in the fridge fr up t 8 days (recmmended if direct mailing is nt feasible); freezing shuld be avided. 17

18 B. Manure histry This test is nt meant as a ne-time measurement; it is mst effective when used fr multiple years n the same field (r fields with similar histries) t determine hw the fields respnd t the way N is being managed. Hwever, if fields test 3 ppm r higher in CSNT, there will be pprtunities t cut N applicatin rates withut impacting yield after just ne year f results. Crp histry, manure histry, ther N inputs, sil type, and grwing cnditins all impact CSNT results and crp management recrds that include these pieces f infrmatin can be used t evaluate CSNT results and determine where changes can be made. Manure will release N ver time and this N supply will be reflected in the CSNT results. C. Crp rtatin It is nt recmmended t take CSNT samples fr 1 st year crn after hay as 1 st year crn fields d nt need the extra N while the slwer release f N frm rganic surces (such as the rts and bimass f a hay field), typically results in lwer CSNT results. T avid cnfusin, sample 2 nd r higher year crn fields after hay, cntinuus crn r crn after sybean fields nly. D. Fertilizer rate, methd f applicatin and timing Nitrgen supply is reflected in CSNT results (in additin t weather and ther pssible stress factrs) s fertilizer rate, methd f applicatin and timing all impact CSNT results. It is imprtant t apply the 4Rs (see PO#52) fr ptimum yield, quality and reduced risk f N lss t the envirnment. Cmpetency Area 4: Nutrient Surces, Analyses, Applicatin Methds 26. Describe the fllwing crp respnse relatinships: a. Diminishing returns respnse curve b. Plateau yield c. Critical respnse level d. Ecnmic ptimum nutrient rate Crp yields depend n many different factrs including sil prperties, genetics, climate, crp management (cultural practices, pest and disease management), and fertility management. Assuming gd crp management and reasnable grwing cnditins, a crp respnse t fertility management culd be expected fr sils that are relatively lw in a specific nutrient. Fr example, if nitrgen is limiting yield, additin f N will result in a crp respnse. Trials with multiple N rates can then be used t determine the ecnmic ptimum nutrient rate. Such trials cnsist f multiple rates f N (typically at least 5 rates) where yield data can be used t 18

19 determine the plateau yield, the critical respnse level and the diminishing returns respnse curve. An example is shwn belw. In this example, when fertilizer was applied t a lw fertility field, yield increased (phase A) until a plateau was reached (phase B). Applying mre fertilizer than needed des nt increase yield (phase C) and culd, in sme situatins, cause a yield decline (phase D; nt cmmnly bserved in field crps). Often, additins f excess fertilizer als increase the likelihd f lsses t the envirnment (see PO#51). The crp respnse curve will be different fr each crp and field, s develpment f a crp fertilizer recmmendatin system requires assembly f data frm many field crp respnse trials. Tgether such trials result in identificatin f critical respnse levels (critical agrnmic test levels) beynd which a respnse t additinal fertility is unlikely t result in a yield increase. Ging frm A t B in the figure abve, the ecnmic ptimum nutrient rate takes int accunt the diminishing return t added fertilizer, and is set where the next additin f fertilizer csts mre than the return in yield is wrth. Thus, the mst ecnmic rate f fertilizer is slightly lwer than the fertilizer rate at which a maximum yield is btained. 27. Describe the rle f the fllwing in prviding plant nutrients: A. Sil rganic matter E. Cmpst B. Cmmercial fertilizer F. Bislids C. Sil minerals G. Plant residue D. Animal manure Sil rganic matter and rganic amendments such as animal manure, cmpst and bislids release nutrients ver time thrugh micrbial mineralizatin. Sil minerals and rganic matter create negatively charged surfaces that attract nutrient catins (catin exchange capacity). Sils differ in their mineral cmpsitin and rganic matter cntent, resulting in differences in their capability t prvide essential minerals t plants. Cmmercial fertilizer is recmmended nly when nutrient supply frm ther surces is insufficient. Plant residues release nutrients back t the sil. Residue cverage f the sil can furthermre result in misture cnservatin and added misture can make nutrients mre available. 28. Describe the physical frm and analysis f each f the fllwing nitrgen surces: A. Anhydrus ammnia D. Urea/ammnium nitrate B. Urea slutin (UAN) C. Ammnium nitrate E. Ammnium sulfate See Describe the physical frm and analysis f each f the fllwing phsphrus surces: A. Rck phsphate D. Diammnium phsphate B. Triple superphsphate E. Ammnium plyphsphate C. Mnammnium phsphate See Describe the physical frm and analysis f each f the fllwing ptassium surces: A. Ptassium chlride C. Ptassium nitrate B. Ptassium sulfate D. Ptassium magnesium sulfate 19

20 Cmmn frms f N, P and K fertilizers (sme have ranges, e.g., UAN is 28-32% N): N: anhydrus ammnia (gas) urea (granular) ammnium nitrate (slid r liquid) urea ammnium nitrate (UAN) slutin ammnium sulfate (slid) P2O5: rck phsphate (slid) triple super phsphate (slid) mnammnium phsphate (slid) diammnium phsphate (slid) ammnium plyphsphate (liquid) K2O: ptassium chlride (muriate f ptash) (slid) ptassium sulfate (slid) ptassium nitrate (slid) ptassium magnesium sulfate (slid) NH3 (NH2)2CO NH4NO3 Urea+ NH4NO3 (NH4)2SO4 Ca(H2PO4)2 Ca(H2PO4)2 NH4H2PO4 (NH4)2H2PO4 [NH4PO3]n KCl K2SO4 KNO3 K2SO4 MgSO4 N P2O K2O % Mg 31. Describe the physical frm and analysis f each f the fllwing calcium and/r magnesium surces: A. Calcitic lime C. Gypsum B. Dlmitic lime D. Ptassium magnesium sulfate Chemical name Cmmn Name Chemical Frmula Physical frm Calcium carbnate calcitic lime, CaCO3 slid Ca,Mg carbnate dlmitic lime CaMg(CO3)2 slid Calcium xide lime, burned lime, quick lime CaO slid Calcium sulfate gypsum CaSO₄ 2H₂O slid dihydrate Ptassium Ptassium magnesium K2SO4 2MgSO4 slid magnesium sulfate sulfate (langbeinite) Calcium hydrxide hydrated lime, slaked lime Ca(OH)2 Slid 32. Define the fllwing cmmercial fertilizer terms: A. Nutrient use efficiency D. Guaranteed analysis B. Ttal availability E. Salt effect C. Water slubility F. Density Nutrient use efficiency is the yield utput per unit input (e.g. bushels f crn per lb f applied N). Ttal availability is the ttal amunt f a nutrient that is eventually expected t becme plant available (culd be ver many years). Water slubility reflects the prtin that disslves in water (mre immediately available). 2

21 Guaranteed analysis is the minimum amunt f %Ttal N, Available P labeled as % P2O5, and sluble K labeled as %K2O (etc.) in the fertilizer material. By law, fertilizer analyses are always labeled in these terms regardless f the actual chemical frm f the fertilizer materials. Sluble salts are salts in the sil slutin, in direct cntact with rts. High sluble salt cntent (resulting frm e.g. large applicatins f N (ammnium salts) and K surces) can cause seedling damage (dehydratin). Fr liquid fertilizers where the rate is given in gallns per acre the density f the fertilizer must be knwn t determine the amunt f nutrients applied per acre. Fr example, if the recmmendatin calls fr 12 lbs N/acre and the surce is UAN 3-- that weighs 1.85 lbs/galln, the applicatin rate is calculated in the fllwing way: 12 lb N/A.3 lb N/lb UAN 1.85 lb UAN/galln = 37 gallns f UAN /acre. 33. Define the fllwing nutrient terms: A. Ttal Kjeldahl nitrgen (TKN) B. Organic N C. Inrganic N D. Organic P E. Inrganic P F. Disslved P G. Particulate P Ttal Kjeldahl nitrgen (TKN): Ttal N analytical methd that includes rganic fractin fr sils, plants and waters. Sils range frm.5 t.3 % typically, but can be several % fr mucks. Plants are nrmally.2 t 4 % depending n species, age, plant part, etc. Organic N: Nt water sluble, rganically bund (e.g. prtein), slw t becme available. Availability based n mineralizatin f rganic matter. Inrganic N: e.g. ammnium, urea, nitrite, nitrate. Organic P: P bund in rganic frm, nt sluble, mst cmmnly fund as phytate. Largest P fractin in animal manure, availability based n mineralizatin f rganic matter. Inrganic P: P nt assciated with carbn (usually P disslved in slutin as PO4 3-, HPO4 2-, H2PO4 - ). Disslved P: P in the sil slutin (PO4 3-, HPO4 2-, H2PO4 - ). Particulate P: P attached t sil particles. 34. Calculate fertilizer applicatin rates frm fertilizer analysis infrmatin. Example 1: Needed: 45 lb N, 45 lb P2O5, 45 lb K2O per acre Determine rati: 1:1:1 (N: P2O5: K2O) Apply (example): e.g. 3 lb/acre f

22 Example 2: Needed: 15 lb N, 3 lb P2O5, 12 lb K2O per acre fr crn Apply (example): K preplant (bradcast) 15 lb/acre 61 = 91 Starter 2 lb/acre = Sidedress UAN* 37 galln 3 = 12 This gives us: * Fr liquid fertilizers where the rate is given in gallns per acre the density f the fertilizer must be knwn t determine the amunt f nutrients applied per acre. In this example, UAN 3-- weighs 1.85 lb/gal. Therefre, 37 gallns/ acre equals 37 x 1.85 = 41 lb f UAN/acre and thus at 3% N, this equals 41 x.3 = 12 lb N/acre. 35. Calculate manure applicatin rates frm manure analysis infrmatin. Althugh cncepts f N availability ver time are accepted in all states in the Nrtheast, actual N credits may differ frm state t state. Refer t state specific Land Grant University guidance. The fllwing examples and the figure belw are frm wrk by Stu Klausner and clleagues at Crnell University and represent the existing New Yrk guidelines fr manure N. Manure cntains varius N pls that can be Urine Ammnium N (fast N) Ttal Manure Nitrgen Mineralized slwly during the year f applicatin separated int a (stable r slw ) rganic N fractin and (unstable r fast ) ammnium-n fractin (see figure frm Klausner, 1997). Bth N pls behave very differently (with differences in N release fr plant grwth) and a manure analysis shuld be used and include an estimate f bth majr N pls. These tw pls are generally listed as rganic N and inrganic N r ammnium-n n manure test reprts. The decay series fr stable rganic N in manure is by animal type. T determine the amunt f N that is expected t be available t the current crp it is necessary t accunt fr the N frm the applicatin t this crp plus any residual N that is expected t be available frm manure applicatins in the recent past. The table belw prvides the factrs t estimate the N frm the present and past applicatins. The present year factr is multiplied by the amunt f rganic N applied in the present year. A last year factr f 12% indicates that an estimated 12% f the rganic N applied in the manure last year is expected t be utilized by the present crp a year after applicatin. Therefre, this factr is multiplied by the amunt Feces Organic N (slw N) Ammnium N Mineralized Available N = frm present + rganic N frm + applicatin present applicatin Residual mineralized very slwly during future years Mineralized rganic N frm past applicatins 22

23 f rganic N applied in the manure last year. Likewise, if manure was applied 2 years ag. In rder t calculate a manure rate fr a current crp, nce the cntributin f N frm the past manure applicatins has been estimated this shuld be subtracted frm the current year N recmmendatin alng with any fertilizer N that may be applied in additin t manure (e.g. starter fertilizer N) and any legume credit frm a previus legume crp. The result will be the net N requirement that culd still be met with the current manure applicatin. Crnell guidance fr manure rganic N release by animal type (Klausner, 1997, derived frm wrk by Klausner et al., 1994). Release rate fr rganic N in manure (%) Surce Dry Matter Cntent (%) Present Year Decay_current Last Year Decay_lastyr Cws < Cws Pultry < Pultry Swine < Swine Hrses < Hrses Sheep < Sheep Tw Years Ag Decay_2yrs Once the net N requirement is calculated, the availability f the N frm the planned applicatin must be estimated. This is determined frm the ammnium and rganic N analysis f the manure and the applicatin management. The availability f the rganic N is determined by multiplying the rganic N analysis times the apprpriate present year Decay Current factr in the table abve. The ammnium N availability is determined by multiplying the ammnium N analysis times the apprpriate Ammnium N utilized by the Crp factr in the table belw. The tw available N amunts are added tgether and this is the available N fr this manure. This is then divided int the Net Crp N Requirement t determine the N balanced manure rate. This rate shuld meet the N requirements f the crp. N mre than this rate shuld be applied. If a lwer rate is selected additinal supplemental N fertilizer may be required. Crnell guidance fr estimated ammnia-n lsses as affected by manure applicatin methd (Klausner, 1997, derived frm wrk by Lauer et al., 1976). Ammnium N utilized by the Crp (% Manure Applicatin Methd Ammnia-N lss (%) Ammnium N utilized by the Crp (%) Injected during grwing seasn 1 Incrprated within 1 day Incrprated within 2 days Incrprated within 3 days Incrprated within 4 days Incrprated within 5 days N cnservatin/injected in fall 1 23

24 Example calculatin f manure applicatin rates frm manure analysis infrmatin: Crp N Recmmendatin: 15 lb N/acre. Starter fertilizer: 15 lb/acre s 15 lb N/acre. Legume N credit frm previus sybean crp: 3 lb N/acre. Residual N frm previus manure applicatins: 2 lb N/acre. Last year: 2 tn dairy manure/acre, 4 lb ammnium N and 6 lb rganic N/tn, 15% slids 2 tn/acre x 6 lb rg. N/tn x.12 = 14 lb N/acre frm last year 2 years ag: 2 tn dairy manure/acfre, 4 lb ammnium N and 6 lb rganic N/tn, 15% slids 2 tn/acre x 6 lb rganic N/tn x.5 = 6 lb N/acre frm 2 years ag Net crp N requirement: 15 lb N/acre - 15 lb N/acre - 3 lb N/acre - 2 lb N/acre = 85 lb N/acre Planned manure management: applied in the spring and incrprated within 3 days Current manure analysis: 1 lb ttal N, 4 lb ammnium N, 6 lb rganic N/tn, 15% slids. Available ammnium N: 4 lb NH4-N/tn x.41 = 1.6 lb NH4-N/tn available. Available rganic N: 6 lb rganic N/tn x.35 = 2.1 lb Organic N/tn available. Ttal available N: 1.6 lb NH4-N/tn lb rganic N/tn = 3.7 lb available N/tn. N balanced manure rate: 85 lb N/accre 3.7 lb available N/tn = 23 tn/a. If the farmer had his spreader calibrated fr the 2 tn/acre rate, this wuld apply: 2 tn/acre x 3.7 lb available N/acre = 74 lb N/acre, abut 11 lb N/ acre shrt (85 lb N/A - 74 lb N/acre = 11 lb N/acre) 36. Describe advantages and limitatins f the fllwing fertilizer placement methds: A. Injectin F. Fliar applicatin B. Surface bradcast G. Sidedress C. Bradcast incrprated H. Tpdress D. Banding (different depths) I. Seed placement (ppup) E. Fertigatin J. Starter band Methd Advantages Limitatins Injectin Reduce lsses Slw, expensive Surface bradcast Fast, ecnmical Higher lsses Bradcast incrpratin Reduce lsses Slw, ersin Band applicatin High nutrient use efficiency Cstly, slw Fertigatin High nutrient use efficiency Irrigatin equipment needed Fliar Rapid uptake Phytxicity, expensive, limited t small and/r repeated applicatins Sidedress High nutrient use efficiency Timeliness, slw Tpdress High nutrient use efficiency Lsses likely Seed placed Lwer equipment csts, starter effect greater than just meeting nutrient requirements Phyttxicity; nly small amunts t avid burn r salt damage t the seedlings Starter band High nutrient use efficiency Only small amunts t avid burn r salt damage t the seedlings, slws dwn planting 24

25 37. Describe hw the fllwing nitrgen additives impact N behavir and management: a. Urease inhibitrs b. Nitrificatin inhibitrs c. Cntrlled release prducts In times f high prductin csts and price vlatility fr bth crp inputs and cmmdity prices, there is an increasing interest in the use f nitrgen (N) surces that reduce the risk fr N lss. Varius technlgies have been develped t minimize the ptential fr N lss t the envirnment, including thse that delay nitrificatin (nitrificatin inhibitrs), delay cnversin f urea t ammnium (urease inhibitrs), and/r emply sulfur r plymer catings t allw release N ver a lnger time perid (slw r cntrlled release). A. Urease inhibitrs Urease inhibitrs are substances that inhibit cnversin (hydrlysis) f urea t ammnia and carbn dixide, reducing ammnia vlatilizatin lsses. Urease inhibitrs can be effective fr up t ten t furteen days. Urease inhibitrs especially target N surces that have a high vlatilizatin ptential (e.g. urea) in situatins in which tillage incrpratin is nt pssible (e.g., n-till, pasture, and grass hay prductin). Adding a urease inhibitr allws mre time fr rain t incrprate the N fertilizer. An example f a urease inhibitr is Agrtain (Agrtain Internatinal LLC) with NBPT (N-butyl thiphsphric triamide) as the active ingredient. B. Nitrificatin inhibitrs Nitrificatin inhibitrs are substances that inhibit cnversin (bilgical xidatin) f ammnium t nitrate. Nitrificatin inhibitrs wrk by keeping N in ammnium frm, which is dne by inhibiting Nitrsmnas bacteria, delaying cnversin fr fur t ten weeks depending n sil temperature and ph. These inhibitrs can reduce N lss frm leaching and denitrificatin but are nly effective n fertilizers that either cntain r are cnverted t ammnium, including anhydrus ammnia, urea, and ammnium sulfate. In the humid climate f the Nrtheastern US, nitrificatin inhibitrs have the highest likelihd fr a yield respnse when applied at planting in less well drained sils (where denitrificatin lsses are mre likely t ccur) r in sandy sils (where the leaching ptential is high). They are less likely t prevent lss when N is sidedressed. Examples f cmmercially available nitrificatin inhibitrs are N-Serve r Instinct (Dw AgrSciences) with nitrapyrin as the active ingredient, and Guardian (Cnklin), with dicyandiamide (DCD) as the active ingredient. Nitrificatin inhibitrs can be added t slid fertilizers. The mixture shuld be applied quickly after mixing t avid vlatilizatin f the inhibitr. C. Cntrlled-release fertilizers Cntrlled-release fertilizers are usually cmmn fertilizers such as urea, cated with a plymer r with sulfur. The cating delays the availability f the nutrients fr plant uptake after applicatin and cntrls nutrient release ver time. These enhanced-efficiency fertilizers allw fr better timing f N release, cnsistent with crp grwth and N demands. Fr sulfur-cated fertilizers, N is released upn the physical breakdwn f the sulfur cating fllwed by sil micrrganisms cmpleting the degradatin and N release prcess. Fr plymer-cated fertilizer, N is released when water enters the granule and disslves the urea r ther N frms inside it int a liquid N slutin, and the slutin diffuses thrugh the cating int the sil slutin. The N diffusin rate is influenced by sil temperature; mre N is released during warmer, active grwing perids and less in cler, inactive perids. There are advantages and ptential disadvantages fr the use f cntrlled-release fertilizers. They can reduce leaching, denitrificatin and/r vlatilizatin lsses, and can result in mre unifrm grwth because f reduced risk f seedling 25

26 burn r salt damage. Hwever, these prducts tend t be mre expensive per unit f N and are nt desirable when a quick release is needed, fr example, when sidedressing crn at the 6-leaf stage. In additin, sme prducts, if applied n bare sil, shuld be incrprated t prevent runff with heavy rains. Sme examples f cntrlled-release urea are ESN (Agrium), Osmcte (Sctts), and Isbutylidene diurea (IBDU, made by Nu-Gr). 38. Recgnize nutrient surces that can be certified rganic. Check with the apprpriate rganic certificatin agency. Cmpetency Area 5: Sil ph and Liming 39. Define: A. Sil ph B. Buffer ph C. Exchangeable acidity D. Alkalinity Sil ph ph is the negative lg f the H+ in cncentratin ph = -Lg H + = lg 1/H + ph 7. = -lg.1 H + r (H + ) = 1 x 1-7 ph 6. = -lg.1 H + r (H + ) = 1 x 1-6 Prperties f ph: ph 7 is neutral - neither acid r basic (alkaline). ph < 7 is acid and > 7 is basic (alkaline). 1 ph = A 1 fld increase in acidity. ph 5 is 1 times mre acid than 6, 1 times mre acid than 7 Sils range between ph 3.5 and 9. a. Hydrgen and aluminum ins and cmplexes are the tw primary surces f sil acidity. b. ph Nrtheastern mineral sils c. ph Nrtheastern muck sils Exchangeable acidity is a measure f the sil s ability t withstand a change in ph upn lime additin. The higher the exchangeable acidity f a sil, the mre lime is needed fr a particular ph change. Buffer ph is used t estimate a sil s exchangeable acidity; the amunt f change in buffer ph is related t lime needs. Alkalinity is the term used t describe the amunt f base in a sil when the ph is abve Describe the lng-term change in sil ph frm applying N. Nitrificatin r the cnversin f ammnium N t nitrate N prduces acidity: 2 NH O2 2 NO H + + H2O 2 H + are prduced fr every N in the ammnium-n frm (NH4 + ). This reactin ccurs regardless f the surce r the NH

27 N surce Theretical lb CaCO3/lb N Official (AOAC) lb CaCO3/lb N Anhydrus ammnia Urea Ammnium nitrate Ammnium sulfate Mnammnium phsphate Diammnium phsphate The acidity frm N fertilizers is ften the largest single acidifying additin t agricultural sils. The net amunt f acidity created when N fertilizer is applied depends n ther reactins that ccur with the fertilizer. The acidity created by different fertilizer materials is summarized in the table, abve. As an example, if 15 lb N/acre is applied as urea, this will prduce the equivalent f 27 lb f lime requirement (15 x 1.8 = 27). Similarly if 15 lb N/acre is applied as ammnium sulfate, 81 lb f lime requirement (15 x 5.4 = 81) will be created. 41. Describe hw applying N in a n-till r lng-term perennial frage crp results in ph stratificatin (acid rf) and hw this impacts rt grwth, herbicide activity, sil sampling, and liming management. The reactin f ammnium frming fertilizers (e.g. ammnium nitrate, urea, urea ammnium nitrate, anhydrus ammnia, ammnium sulfate) with xygen (a prcess called xidatin) results in the frmatin f nitrate (NO3 - ) and H + ins which lwers sil ph: 2 NH3 + 4 O2 2 NO H H2O (ammnia) (xygen) (nitrate) ( acid ) (water) NH4NO3 + 2 O2 2 NO H + + H2O (ammnium nitrate) (xygen) (nitrate) ( acid ) (water) (NH2)2CO + 2 O2 2 NO H + + H2O (urea) (xygen) (nitrate) ( acid ) (water) (NH4)2SO4 + 4 O2 2 NO3 - + SO H H2O (ammnium sulfate) (xygen) (nitrate) (sulfate) ( acid ) (water) In n-till situatins, the fertilizer is nt mixed thrughut the sil prfile, and cnsequently, the acidity created by this fertilizer remains at the surface, resulting in the frmatin f an acid rf where the surface inch r tw f sil is lwer in ph than the subsil. This can impact rt grwth, especially fr new seedings, as well as impact herbicide activity. Under minimum r n-tillage systems, because the surface inch f the sil may becme acid mre rapidly than the deeper layer, the ph values f tw sil layers (-1 and -6 inches) shuld be determined. If the ph f the surface -1 inches is less than desired, but the ph f the 6-inch cre is adequate, a small lime additin (1 t 1 ½ tns f lime per acre) is recmmended t raise the ph f the sil surface. If bth samples are strngly acidic, d nt use n-till methds fr the establishment f legumes unless lime has been applied and mixed with the sil fr at least 6 t 9 mnths t permit the lime t react with the sil. If the surface ph is adequate, but the ph f the 6-inch cre is lwer than desired, legumes might be n-till seeded with a slightly lwer verall ph r withut waiting s lng fr the applied lime t react as when bth znes have a lw 27

28 sil ph. Dwnward mvement f lime t subsurface layers is very slw and nly ccurs after the surface layer has reached >8% saturatin which means the ph f the surface needs t be arund 7. t let lime t mve dwnward. If a rapid increase in ph is desired, a very finely grund limestne can be used r hydrxide surces (hydrated lime r slaked lime) can be cnsidered. Bth will be mre expensive than planning ahead and maintaining a gd ph level ver time. As explained, these surces increase the ph f the sil much faster than calcitic r dlmitic limestnes. This culd be desirable if a quick increase in ph is needed. Hwever the effects are f shrter duratin. 42. Describe hw catin exchange capacity (CEC), sil texture, exchangeable acidity and sil rganic matter affect lime requirements. Lime requirements increase with CEC and a sil s CEC increases with rganic matter and clay cntent. Thus, clay sils with high rganic matter require mre lime fr a similar ph change than sandy sils lw in rganic matter. In ther wrds, high CEC sils tend t be well-buffered, meaning they are resistant t ph changes and as a result, require mre lime t change the ph. Sandy sils are prly buffered, requiring less lime per unit ph change. Hwever, because f the greater buffering capacity, the sil ph will decrease slwer n higher CEC sils than in prly buffered sandy sils. 43. Describe hw sil ph affects the availability f each nutrient. Mst plants usually grw best at ph values abve 5.5. Lwer ph increase slubility f Al, Mn, Fe. a. In excess Al, Mn, Fe are txic t plants. b. A critical effect is that rt grwth is slwed r stpped by excess sluble Al. Extreme ph values decrease the availability f mst nutrients. The ph versus availability f nutrients effect f sil ph n nutrient Very Very Med. Slightly. Slightly Med. Strngly Acid Slightly Slightly Strngly Alkaline Acid Acid Acid Alkaline availability is summarized in the Nitrgen Alkaline Alkaline figure belw. Lw ph reduces the availability f the macr and Phsphrus Ptassium secndary nutrients. High ph Sulfur reduces the availability f mst micrnutrients. Calcium Magnesium Sil ph arund 6.5 is usually Irn cnsidered ptimum fr nutrient availability. Manganese Brn Cpper and Zinc Micrbial activity may be affected Mlybdenum by very lw r very high ph. 44. Describe hw liming materials increase sil ph Limestne is calcium carbnate and magnesium carbnate CaCO3 and MgCO3 The limestne disslves in water t frm carbnic acid (H2CO3) and Ca(OH)2: CaCO3 + HOH H2CO3 + Ca(OH)2 H2CO3 is unstable and cnverts t carbn dixide and water - the CO2 gas escapes H2CO3 CO2 + HOH 28

29 The remaining Ca(OH)2 dissciates int Ca 2+ and OH - The Ca 2+ replaces 2 H + frm the sil; increasing the sil base saturatin The OH anin reacts with the sil acid catin H+ frming water H + + OH - HOH (water) 45. Describe hw purity, fineness, and calcium carbnate equivalent (CCE) affect the neutralizing ability f liming materials. Calcium Carbnate Equivalent (CCE) - The neutralizing value f a liming material cmpared t pure calcium carbnate. A CCE f 1% indicates the material will neutralize the same amunt f acidity per pund as pure calcium carbnate. Fineness - the finer a limestne is grund, the faster it will react in the sil. Fineness is reprted as a particle size distributin usually as the percentage f the material that will pass 2, 6, and 1 mesh screens. An example f the size distributin fr a typical gd quality limestne is: 95% passing 2 mesh; 6 % passing 6 mesh; 5% passing 1 mesh. A particle size distributin such as this is a gd cmprmise between cst, practical agrnmic effectiveness and medium term maintenance f ph. Material larger than 2 mesh reacts t slw t be f much value as a liming material. All very fine, less than 1 mesh material, will react quickly but it will be much mre expensive and may be difficult t handle and the sil ph will decrease faster because there is a lack f larger lime particles available t breakdwn ver time. Fineness des nt increase the ttal neutralizing value f a limestne, just hw fast it will react. Effective neutralizing value (ENV) f a limestne is determined by its calcium carbnate equivalent (CCE) multiplied by its particle size distributin expressed as fineness. Limestnes react at rates prprtinal t the surface area f the particles. The ttal surface area f the particles is related t the size f lime particle. 1% f lime that passes 1 mesh screen will react in 1 yr. 8% f lime that passes 6 but held n 1 mesh will react in 1 yr. 4% f lime that passes 2 but held n 6 mesh will react in 1 yr. The Calcium Carbnate Equivalent is the reactive prtin f the lime. 29

30 T determine the ENV f a limestne: Subtract the % passing 6 mesh frm the % passing 2 mesh and multiply by.4. Subtract the % passing 1 mesh frm the % passing 6 mesh and multiply by.6. Multiply the % passing 1 mesh by 1.. Add the abve 3 numbers t btain the fineness factr. It shuld be less than 1%. Multiply the abve number by the CCE in decimal frm t get the ENV. The ENV shuld be between abut 3 and 1 fr pulverized limestnes sld in NY. Limestne #1 Calcium Carbnate Equivalence (CCE) % Calcium (% Ca) 2.8% Magnesium (% Mg). 8.% Particle Sizes 98% passing 2-mesh sieve 9% passing 6-mesh sieve 7% passing 1-mesh sieve Effective Neutralizing Value (ENV) 7.3 Weight required fr 1% effectiveness 1.4 Instructins Line 1. Enter % limestne passing 1-mesh Line 2. a) Enter % passing 2-mesh sieve b) Enter % passing 6-mesh sieve c) Subtract values n line 2b. frm 2a. and enter here d) Multiply value n line 2c. by.4 and enter result. Line 3. a) Enter % passing 6-mesh sieve (same as line 2b) b) Enter % passing 1-mesh sieve (same as line 1). c) Subtract 3b frm 3a and enter here d) Multiply value n line 3c by.8 and enter here Line 4. Sum lines 1, 2d, + 3d and enter n line 4 Line 5. Enter calcium carbnate equivalence (CCE) in decimal frm,.i.e, CCE+ 1. Limestne #2 Calcium Carbnate Equivalence (CCE) 14.3% Calcium (%Ca) 2.8% Magnesium (% Mg). 12.5% Particle Sizes 98% passing 2-mesh sieve 8% passing 6-mesh sieve 75% passing 1-mesh sieve Effective Neutralizing Value (ENV) 89.9 Weight required fr 1% effectiveness 1.1 Limestne effectiveness value scre card The infrmatin needed fr the calculatins f the limestne effectiveness value (ENV) is shwn n the label r n the delivery sheet. Tw examples f the calculatins fr the limestnes are listed. Scre Card Limestne#1 Limestne#2 1. Passing 1-mesh a. Passing 2-mesh b. Passing 6-mesh 9 8 c. 2-6 mesh 8 18 d. 2- t 6 mesh reactin value X a. Passing 6-mesh 9 8 b. Passing 1-mesh 7 75 c. 6- t 1-mesh 2 5 d. 6-t 1-mesh reactin value X Fineness scre Line 6. Line 7. Multiply line 4 by line 5 and enter n line 6. This is the effective neutralizing value. Divide 1 by the ENV (line 6) and enter On line 7. This is the quantity f lime required t equal 1 unit (i.e. 1 tn r 1 lb) f 1% ENV. 5. % Calcium Carbnate Equivalence / ENV Weight equivalent t 1% ENV Line 8. Enter the cst f 1 tn f lime n line 8. 3

31 Line 9. Multiply amunt n line 8 by line 7.This is the cst f 1 tn f 1% ENV lime and prvides the cst cmparisn f each material fr the quantity f material that will react with the sil within the 1 st year. Cst Effectiveness 8. Cst per tn Cst per tn f 1% ENV Calculate lime applicatin rates t meet lime requirements. Lime recmmendatins are given in 1% ENV. T cnvert t lime recmmendatin fr a particular liming material A: Lime rate (tns/acre) = 1 x lime rate fr 1% ENV (tns/acre) / ENV f material A. Fr example, the sil test recmmendatin is 1.5 tn/acre f 1% ENV and the limestne has an ENV f 7.3. Hw much f this material needs t be added? Answer: Lime rate (tn/acre) = 1 x 1.5 tn 1% ENV 7.3 ENV = 2.1 tns limestne/acre Calculated value Aglime Quality - ENV CCE * Fineness Must be listed n bag and/r delivery slip Crnell recmmendatins are fr 1% ENV Recmmendatin Actual lime required = *1 ENV f limestne 47. Understand hw bislid applicatin and sil ph affect availability f heavy metals t plants. In general, heavy metal availability is highest at lw ph s liming can decrease heavy metal availability while heavy metals, if present, culd becme txic at lw ph. Bislids can cntain heavy metals while sme bislids might als be lime-stabilized, resulting in a ph increase upn applicatin. 31

32 Cmpetency Area 6: Nutrient Management Planning 48. Describe hw t set a realistic yield gal by using: A. Prductin histry D. Sil type B. Sil prductivity E. Artificial drainage C. Management level F. Sil nutrient use efficiency Fertility practices shuld be based n realistic yield gals, als called yield ptential, recgnizing inherent limitatins t yield. Yield ptentials take int accunt prductin histry, sil prductivity, management level, sil type and artificial drainage. Artificial draining can increase yields fr sils that are, by nature, prly drained. Yield ptentials are btained by averaging yields btained 4 ut f 5 years, discarding extreme years (e.g. due t severe drught). Realistic yield gals shuld take int accunt nutrient use efficiency (ability f the plants t make use f the nutrients in the sil) as it will nt be ecnmically r envirnmentally viable t fertilize fields with very lw nutrient use efficiency. 49. Determine crp nutrient needs by using: A. Yield ptential B. Crp rtatin/sequence C. Sil nutrient supply D. Sil test infrmatin E. Field histry F. Field-specific N testing (e.g., pre-sidedress nitrate test, crn G. Stalk nitrate test, Illinis sil nitrgen test) Nitrgen recmmendatins in the Nrtheast are nt based n a sil nitrate test as nitrate is very mbile in the sil. Fr nitrgen, crp nutrient needs are usually derived based n infrmatin abut the yield ptential f a field (ideally based n histric yield data), its place in the crp rtatin, estimated sil N supply frm mineralizatin f rganic matter, and management histry f the field, especially when manure is applied in previus years. The final recmmendatin needs t be adjusted fr N fertilizer uptake efficiency recgnizing that nt all N applied will end up in the crp. Fr example, N requirement fr crn in New Yrk is calculated as: N = ([yield ptential (bu/acre) x 1.2] sil N supply sd N supply)/n uptake efficiency Example: 3 rd year crn after alfalfa n manure applied in any f the previus 3 years sil = lima (tiled drained) sil N = 75 lbs/acre yield ptential = 14 bu/acre sd N = 1 lbs/acre N uptake efficiency = 7% manure N = lbs N = ([14 x 1.2] 75-1) /.7 = 119 lbs/acre Nitrgen frm sd becmes available thrugh mineralizatin and nitrificatin. N availability frm crp residues varies depending n sd cmpsitin and year since terminatin. Fr example, in New Yrk the fllwing N credits frm sd are applied t crn fllwing sd: 55% - 12% - 5% f ttal N fr the 1 st, 2 nd, and 3 rd year, respectively. 32

33 Fr ttal amunt, multiply the decay series value by the estimated ttal N pl in the sd (dne in the table belw). Expected N credits frm plwed dwn sds. Available N Legume in sd Ttal N pl Year 1* (55%) Year 2 (12%) Year 3 (5%) % lbs N/acre lbs N/acre lbs N/acre lbs N/acre r mre * First year fllwing plw dwn. Sil nutrient supply f P, K, Mg, etc., is evaluated using a sil test. Fr N, several tls can be used t guide decisin making beynd the base recmmendatins develped with the apprach utlined abve. These tls include the pre-sidedress nitrate test (PSNT), the crn stalk nitrate test (CSNT), and the Illinis sil nitrgen test (ISNT). The PSNT and ISNT are sil-based assessments that guide decisins prir t N applicatin. The CSNT is an end-f-seasn test equivalent t a reprt card that allws a prducer t evaluate if N applicatins, as implemented that year, were insufficient, sufficient, r excessive. Fr mre details n PSNT, see PO#21. Fr details n hw t credit past manure applicatins, see PO# Knw hw t calculate an N r P based manure applicatin rate based n: a. Crp requirements b. Manure analysis c. Planned applicatin methd and timing d. Linkage with supplemental fertilizer applicatin (e.g., starter) Manure cntains all essential nutrients, but in ratis that are nt necessarily what plants need. Fr example, if manure is applied t meet N requirements f a crn crp, P and K will be applied in excess f crp remval (see PO#55). T determine apprpriate manure applicatin rates, it is imprtant t first determine the crp s nutrient needs. The N and P value f the manure can then be determined based n the N and P cntent f the manure, and the planned applicatin methd and timing. Incrpratin f manure in spring, prir t planting a crn crp will increase the amunt f N that is plant available (due t reduced N vlatilizatin when manure is incrprated). Fr mre details n N credits frm manure, see PO#35. T calculate hw much P2O5 and/r K2O are applied with a specific rate f manure, multiply the manure applicatin rate in tns r in 1 gallns by the lbs/tn r lbs/1 gallns f P2O5 in the manure (as is clumn n the manure analysis reprt). If an applicatin, fr regulatry reasns, cannt exceed the equivalent f P2O5 remved with the crp (P-based manure management), first estimate crp remval f P2O5 by multiplying the yield gal by the average P cntent f the crp. Fr example: Estimated P2O5 remval by a 2 tn/acre crn silage harvest at 35% dry matter amunts t 2*2,*35*.61/1,=85.4 lbs P2O5 (an estimated 4.3 lbs P2O5/tn f silage). See fr mre detail and P2O5 cntents f varius field crps. If insufficient N r P is applied with manure, fertilizer applicatins can be dne t ensure sufficient nutrient supply fr the crp. Where initial sil fertility levels are lw, a starter applicatin f N, P2O5 and/r K2O shuld be cnsidered as nutrients frm manure are released mre slwly ver time. 33

34 51. Describe envirnmental effects frm nutrient lss by: A. Ersin D. Denitrificatin B. Runff E. Leaching C. Vlatilizatin Ersin and Runff Because P is held mainly in insluble frms in the sil the predminant mechanism fr P lss is when sil cntaining these insluble minerals is erded. When the erded sil enters water the dilutin effect will slubilize sme f this P which can lead t eutrphicatin. The capacity fr a sil t fix P is very large, hwever it is nt infinite. It is pssible t add enugh P t use up mst f the available Fe and Al, at least in the surface sil. When this happens we say the sil is saturated with P. Thus, additinal P is nt fixed and it remains sluble and can be lst with runff. This becmes very imprtant when large amunts f P are added t the sil surface. The surface layer f sil can becme saturated very quickly and then, when there is runff ver the surface, it interacts with this saturated surface sil layer and picks up significant amunt f sluble P and transprts it ff the field. If this runff ges int a water bdy the P is immediately available t cause eutrphicatin. In very sandy sils with little natural Fe and Al, there is little capacity t hld the P and thus it becmes saturated mre quickly. In these sils sluble P lss is an even greater cncern and even P leaching can be significant. Management t minimize P lss is a cmprmise. Incrprating the P psitins it s that surface runff and ersin will nt have access t the added P thus reducing the ptential fr lss. Als the mixing that ccurs spreads the P ut s that it cntacts mre sils; as a result the sil des nt saturate with P as rapidly. Hwever, tillage t incrprate P usually increases the ptential fr ersin which is the majr lss mechanism fr P. The ideal is t place P belw the sil surface in a way that minimizes sil and residue disturbance. Direct injectin f manure r fertilizer P can be very effective in reducing P lss. Finally, timing can help. Mst P surces are highly sluble when first applied. If a runff r ersin event ccurs immediately fllwing applicatin, lss can be very high. Hwever, with time P reacts with the sil and becmes less sluble. Thus timing P applicatins when it is less likely that yu will have significant runff r ersin events can reduce lsses. Finally, sil prperties which cntrl water mvement can play a very imprtant rle. If a sil is cmpacted r crusted r has a lw amunt f residue cver, mre water will runff increasing the ptential fr P lss. Managing sil drainage can have a similar impact. Vlatilizatin Urea nitrgen (Urea fertilizer, UAN slutin fertilizer, and manure all cntain urea N) is unique in that the available ammnium N (NH4 + ) frm urea can be rapidly cnverted t ammnia (NH3) which is a gas. If this reactin ccurs n the sil surface the ammnia is lst int the atmsphere. Lsses f ver 1/3 f the N frm urea can ccur within ne week f surface applicatin f a urea cntaining material. Tillage r ½ inch f rain that incrprates the urea will minimize this lss. The sner tillage r rain ccurs after applicatin the smaller lsses will be; immediate incrpratin r timing applicatin just befre rain are imprtant t reducing this lss. Other cmmn N surces such as ammnium sulfate and ammnium nitrate are nt susceptible t vlatilizatin lss. Urease inhibitrs have been develped as an additive t urea t effectively reduce the risk f vlatilizatin lss (fr up t 14 days) when incrpratin is nt pssible. Denitrificatin. When sils becme saturated with water, anther N lss called denitrificatin ccurs. This is especially a prblem in prly drained sils. Denitrificatin ccurs when rganisms in a saturated sil begin t run ut f xygen. Sme f these rganisms have develped the ability t extract the xygen frm nitrate (NO3 - ) t survive. In the prcess, N frm nitrate is released as either dinitrgen (N2) r nitrus xide (N2O), gases which are unavailable t plants while N2O is a greenhuse gas with serius envirnmental implicatins. 34

35 Leaching. Mst N surces are rapidly cnverted t nitrate-n (NO3 - ) by bacteria in the sil. This is an imprtant prcess because nitrate is the mst cmmn frm f N taken up by plants. Hwever, since nitrate is an anin (i.e. has a negative charge) it is nt held n the sil CEC, therefre if water perclates thrugh the sil it can easily carry significant amunts f nitrate with it. If the nitrate is leached belw the rting zne f the crp it is n lnger available and if it leaches t the grund water it represents a pllutin prblem with public health implicatins. This is especially a prblem n well drained sils. 52. Describe the basic cncepts f the 4Rs (right surce, right rate, right timing, and right placement). The 4R nutrient stewardship cncept defines the right surce, rate, time, and place fr fertilizer applicatin as thse that prduce the ecnmic, scial, and envirnmental utcmes desired by all stakehlders t the plant ecsystem. The 4R stewardship cncept helps crp prducers and their advisers select the right surce rate time place cmbinatin frm practices validated by research. See: fr mre infrmatin n the 4Rs cncepts. 53. Understand the rle f the NRCS 59 Nutrient Management Standard in natinal nutrient management planning plicy. The NRCS59 Standard establishes criteria fr the nutrient management elements f cmprehensive nutrient management plans (CNMPs) fr Cncentrated Animal Feeding Operatins (CAFOs) and ther farms receiving state r federal cst sharing fr best management practices (BMPs). 54. Define nutrient mass balance and describe why there can be a net excess nutrient mass balance n dairy and livestck farms. See Distinguish P-based frm N-based manure applicatin and describe implicatins. A mass nutrient balance can be described as the difference between ttal amunt f nutrients imprted nt the farm and nutrients exprted via milk, meat, crps, manure, etc. Zer r negative balances are nt sustainable as all bilgic systems have inherent lsses. Due t differences in N, P, K ratis f manure versus crp N, P and K needs, it is difficult t achieve acceptable N, P, and K balances simultaneusly n dairy and livestck farms; balancing field applicatins fr N with manure will increase sil P and K ver time. See the example t the right fr crn and dairy manure. N-P-K Feed INPUT Whle Farm Mass Nutrient Balances N fixatin OUTPUT 35