Irrigated Soft White Wheat

Transcription

1 NUTRIENT MANAGEMENT EM 9015-E December 2010 Irrigted Soft White Whet (Estern Oregon) D.A. Horneck, J.M. Hrt, M.D. Flowers, L.K. Lutcher, D.J. Wysocki, M.K. Corp, nd M. Bohle Soft white whet is grown in vriety of rottions nd lndscpe positions throughout estern Oregon. Recommendtions in this fertilizer guide pply to spring or winter vrieties of soft white whet grown with irrigtion in Bker, Crook, Deschutes, Jefferson, Mlheur, Umtill, Morrow, Wllow, nd Union counties on silt lom, sndy lom, lomy snd, nd snd soil texturl clsses with less thn 3 percent orgnic mtter. The most yield-limiting nutrient for whet is nitrogen. Recommendtions for nitrogen (N), phosphorus (P), potssium (K), sulfur (S), nd micronutrients re included in this guide. Amendments for slt-ffected, cidic, nd lkline soils re lso discussed. The production re covered by this guide is geogrphiclly lrge nd diverse. Soil type, soil depth, crop rottion, mngement, nd climte differ widely cross this re. This publiction provides informtion nd recommendtions suitble for the soil nd climtic conditions cross the region. Use these recommendtions s guide, rther thn prescription. Tke into ccount your own experience with your fields when mking nutrient mngement decisions. Recommendtions for Wshington nd Idho differ from those in this guide. For exmple, the N recommendtions in the Southern Idho Fertilizer Guide for Irrigted Winter Whet re lower thn those in this guide. In some res of estern Oregon, conditions re similr to those in Wshington or Idho. If you know from experience tht this is the cse for your field or frm, use the recommendtions for the pproprite re. Use the N rte recommendtions from the Idho guide if your experience nd grin protein level show tht the lower rtes re sufficient for your sitution. Pest-free plnts with dequte root systems re required to obtin the gretest return from your fertilizer investment. The nutrient recommendtions in this guide ssume tht weeds, insects, nd diseses re controlled. Lck of pest control cnnot be overcome by the ddition of nutrients. This guide is orgnized chronologiclly for cropping seson. Common fertilizer forms of nitrogen, phosphorus, potssium, nd sulfur re 100 percent plnt-vilble t the time of ppliction. For this reson, most nutrients re best pplied shortly before they will be needed. Mngement decisions before plnting Vriety selection Nutrient recommendtions in this guide ssume tht n pproprite vriety is selected for the site. Whet vrieties re vilble tht hve gronomic nd qulity chrcteristics needed to optimize production for your loction. In estern Oregon irrigted production, growers should consider vrieties with high yield potentil, suitble milling qulity, good disese resistnce, nd lodging resistnce. Informtion on the performnce, gronomic, nd qulity chrcteristics of winter nd spring whet vrieties in Oregon cn be found t edu/whet/stte_performnce_dt.htm Plnting dte Winter whet is typiclly plnted from lte September to November. Plnting is delyed until this time to reduce the level of phid infesttion nd the risk of brley yellow dwrf virus, which is trnsmitted by phids. When plnting erlier, n insecticidl seed tretment is recommended to reduce the risk of phid-borne diseses. Whet plnted in November will hve reduced fll growth. Lte plnting cn reduce winter kill in some vrieties. For lte plntings, increse the seeding rte nd consider pplying strter fertilizer with or ner the seed (see pges 4 7). Mike Flowers, Oregon Stte University 1 D.A. Horneck, Extension gronomist; J.M. Hrt, Extension soil scientist; M.D. Flowers, Extension cerels specilist; L.K. Lutcher, Extension gronomist; D.J. Wysocki, Extension soil scientist; M.K. Corp, Extension gronomist; nd M. Bohle, Extension gronomist; ll of Oregon Stte University.

2 In this region, spring whet is typiclly plnted from Februry to My. Where brley yellow dwrf virus nd Hessin fly re common, consider the use of n insecticidl seed tretment when sowing spring whet. Plnting outside these recommended times cn dd stress to whet plnts, thus reducing efficiency of nutrient use. Rottion Whet is grown in rottion with mny crops, including processing vegetbles, peppermint, grss seed, legumes, corn, pottoes, nd onions. Fertilizer ppliction nd nutrient use vry gretly mong crops, creting rnge of soil nutrient vilbility. Whet is well suited for situtions where nutrients from previous crop remin in the soil. With its deep, fibrous root system, whet efficiently extrcts nutrients, especilly N. When whet is plnted fter pottoes, onions, nd mny other vegetble crops, sufficient nutrients re usully vilble for erly whet growth, so preplnt fertilizer ppliction is not needed. Fll soil smpling nd ph djustment Smpling soil Smple soil in the fll regrdless of whether whet will be plnted in fll or spring. For fll-plnted whet, tke smples fter tillge is complete. Smple nd nlyze soil from 1-foot depth to estimte lime, phosphorus, nd potssium requirements. A single smple should represent no more thn 40 cres, single soil type, or n re in the field with the sme mngement prctices. Be creful when compring soil test results from spring nd fll smples, s soil ph cn vry more thn 1 to 2 units nnully, especilly in sndy soil. If you hve questions bout smpling or testing soil, contct your locl Oregon Stte University Extension office or refer to OSU Extension Service publiction PNW 570, Monitoring Soil Nutrients Using Mngement Unit Approch, ctlog/pdf/pnw/pnw570-e.pdf Summry Preplnt mngement Lime A soil ph greter thn 5.5 is recommended. If the soil ph is below 5.4, pply 1 ton of 100-score lime/ if the field s soil texturl clss is sndy lom, fine sndy lom, or lomy snd. For fields tht re silt lom soil texturl clss, increse the lime rte to 1.5 to 2 t/. See pge 3. Nitrogen (N) If winter whet will be plnted fter crop leving limited N in the soil, or if whet is plnted lter thn recommended in the fll, pply 20 to 30 lb N/. Otherwise, no N is needed t plnting. See pge 4. When plnting spring whet, up to 25 lb N/ cn be bnded t plnting. Phosphorus (P) If soil test P is below 20 ppm, pply P ccording to Tble 2. See pge 5. Potssium (K) If soil test K is below 100 ppm, pply K ccording to Tble 6. See pge 7. Sulfur (S) Apply 10 to 30 lb S/ if (1) whet is seeded lte in the fll, (2) greter-thn-verge quntity of strw is present in the field, nd/or (3) the concentrtion of S in irrigtion wter is less thn 5 ppm. See pge 7. Zinc (Zn) Appliction of Zn my be beneficil when DTPA-extrctble soil test Zn is less thn 0.8 ppm. Apply Zn t rte of 1 to 5 lb/. If pplying 1 to 2 lb Zn/, pply in bnd. Brodcst ppliction is recommended when higher rtes re used. See pge 7. Boron (B) Apply 0.5 to 2 lb B/ when soil test B is below 0.4 ppm. See pge 7. Spring nutrient mngement Nitrogen (N) Winter whet: After winter dormncy, smple soil for N nlysis. Collect smples from the effective root zone (usully 2 or 3 feet) in 1-foot increments nd hve them nlyzed for nitrte-n (NO 3 -N). In ddition, hve smples from the top foot nlyzed for mmonium-n (NH 4 -N). Use Tbles 7 nd 9 to clculte spring N rte. See pges Spring whet: Before plnting, smple soil nd hve it nlyzed for nitrte-n nd mmonium-n s described bove for winter whet. Use Tble 9 to clculte N rte. See pges Posthrvest mngement Grin protein Trget for grin protein is 8 to 10.5 percent. See pge 10 for explntion. 2

3 Soil ph djustment Soil ph indictes the chemicl conditions of the soil tht roots will experience. A decrese in soil ph is ccompnied by incresed solubility of iron, zinc, mngnese, copper, nd luminum. In cidic soil, the concentrtion of mngnese nd luminum cn increse to levels tht inhibit root growth. Acidic soils re prevlent throughout estern Oregon. The combintion of high-qulity irrigtion wter nd N fertilizer use hs lowered the ph of mny soils. Sndy soils re cidified fster thn silt lom or finer soil texturl clsses. Even so, silt lom soils in estern Oregon cn hve soil ph too low for optiml whet production. A soil ph bove 5.4 is recommended for whet production. Whet yields re mrkedly reduced when soil ph is less thn 5.0, s shown in Figure 1. Between ph 5.0 nd 5.4, yield vries with vriety, field, nd yer. Figure 1 shows tht whet yield will not be incresed by rising the soil ph bove 5.7. The soil ph for some sndy soils my need to be higher thn 5.3 t plnting becuse soil ph chnges sesonlly. In some cses, ph my be dequte in the fll but drop below 5.4 by spring. For exmple, soil ph cn decrese 2 units between Jnury nd Mrch. This chnge in soil ph mkes smpling time criticl. Smple soil for ph in the fll to determine the need for lime. Incresing soil ph Lime ppliction is recommended to rise soil ph when ph is below 5.4. Apply 1 ton of 100-score lime/ when the field hs sndy lom, fine sndy lom, or lomy snd soil texturl clss. Increse the lime rte to 1.5 to 2 t/ for fields tht re silt lom soil texturl clss. Incorporting lime in the fll is best for both winter nd spring whet, s lime rects slowly to rise soil ph. Decresing soil ph Whet yield cn be reduced if the soil ph is bove 8.7. A soil ph bove 8.5 my be cused by excess sodium in soil. For informtion bout mngement of lkline soil, see the sidebr Decresing soil ph (lkline soils). For informtion bout slt-ffected soils, see the sidebr titled Slt-ffected soils (pge 4). Grin yield (bu/) Soil ph below 5.0 Soil texturl clss, lime rte, nd lime score Soil Soil ph ph bove 5.4 bove Soil ph Figure 1. Grin yield of Nugines whet s relted to soil ph on n cidic western Oregon field. Lime ppliction rtes re bsed on soil texturl clss nd lime score. Where soil orgnic mtter content is low, s in estern Oregon, soil texturl clss is good indiction of soil ph buffering cpcity (resistnce to ph chnge). Lime score is reltive indiction of product s bility to increse soil ph. Lime rtes re bsed on lime score of 100, or pure lime (clcium crbonte). The lime ppliction rte is incresed s lime score decreses. For exmple, sugr by-product lime (sugr lime) commonly hs score of 50. For ny lime product, determine the rte needed to chieve the recommended lime rte by dividing the recommended rte (t/) by the deciml frction score. For 1 t/ lime ppliction nd score of 50, the clcultion would be: = 2. Therefore, if the lime recommendtion is 2 t/ of 100-score lime, nd you use sugr lime ( score of 50), you will need to pply 4 t sugr lime/ (2 0.5 = 4). Decresing soil ph (lkline soils) Alkline soils (high ph) re the product of lndscpe position, climte, nd the chemicl chrcteristics of the soil. High soil ph my lso be cused by poor-qulity irrigtion wter. Whet yield my be reduced when soil ph is greter thn 8.7. Micronutrient deficiencies re common in highly lkline soils. Wter penetrtion cn lso be problem in these soils nd should be ddressed when mking crop mngement decisions. Soil ph cn be reduced by pplying high rtes (1 or more t/) of elementl S, but doing so is rrely economicl. The use of cid-producing fertilizer products, such s mmonium sulfte or mono-mmonium phosphte, my reduce the detrimentl effects of high soil ph. In ddition, bnding fertilizer will increse the solubility of micronutrients in the seed zone. For more informtion bout soil ph mngement nd wter penetrtion in lkline soils, see OSU Extension Service publiction PNW 601-E, Slt-ffected Soils for Crop Production. 3

4 Slt-ffected soils Slt-ffected soils cn result from vriety of fctors climte, lndscpe position, poor dringe, poor-qulity irrigtion wter, nd/or poor wter mngement. Accumultion of slt in irrigted soils cn reduce crop growth nd yield, reduce the effectiveness of irrigtion, ruin soil structure, nd ffect other soil properties. The extent to which slts ffect soil is determined by mesuring electricl conductivity (EC) of both soil nd irrigtion wter. Estimted yield reduction from slt in soil or irrigtion wter is summrized in Tble 1. Tble 1. Yield reductions for whet ssocited with rnge of electricl conductivity (EC) vlues for soil nd wter of the sturted pste extrct.,b Electricl conductivity (sturted pste) Yield (mmhos/cm or ds/m) reduction Soluble slts in soil Wter (%) Below 6 Below 4 Below Over 20 Over Source: Ayers nd Westcot. Wter Qulity for Agriculture. b Not ll lbortories in the Northwest determine soluble slts from sturted pste. Some lbortories use 2:1 or 1:1 wterto-soil, which does not provide vlue tht cn be relted to soluble slts from sturted pste. Whet plnts re most susceptible to injury t erly growth stges (germintion nd emergence). Seedling injury from slts increses when N nd K fertilizers re plced with or ner the seed. Drought stress substntilly increses slt dmge to whet plnts. Slt-ffected soil problems re not esily corrected. Informtion bout mngement nd reclmtion of slt-ffected soil is vilble in OSU Extension Service publiction PNW 601-E, Slt-ffected Soils for Crop Production. Preplnt nutrient mngement Nitrogen (N) Whet requires only smll mount of N from plnting through tillering (Feekes 5), s plnts ccumulte only 20 to 40 lb N/ during this period. However, insufficient N during erly growth limits tiller development nd ultimtely reduces grin yield. See the sidebr N ppliction methods for informtion bout how to pply N. Winter whet For most crop rottions especilly if whet follows pottoes, onions, or lflf nlysis of soil for N content is not necessry before plnting. In most cses, residue from the previous crop will provide sufficient N for erly whet growth. Therefore, N ppliction t plnting is importnt only when whet is plnted following crops tht leve little residul N (for exmple, corn, whet, or ots), or when whet is plnted lter thn recommended. When whet is plnted in situtions where low residul N is possible, collect soil from the surfce foot before plnting to ssess N need. When soil test results for nitrte-n in the top foot re below 20 lb nitrte-n/ following these crops, pply 20 to 30 lb N/ t plnting. Bnding N with the seed is n efficient method of pplying smll mounts of N. If N is not bnded, rtes s high s 50 lb N/ my be wrrnted under high-residue situtions (e.g., corn or whet). Do not bnd more thn 25 lb N/ with the seed. Higher mounts cn be bnded if plced t lest 1.5 inches from the seed. Most of the N needed for growth of winter whet will be pplied in the spring before jointing (Feekes 6). See Spring nitrogen mngement, pges 8 9, for informtion bout timing, rtes, nd ppliction methods. Spring whet For spring whet, see Spring nitrogen mngement, pges 8 9, for informtion bout N timing nd rtes. N ppliction methods Nitrogen fertilizer cn be pplied s bnd t plnting, preplnt incorported, or by fertigtion. Bnding fertilizer ner or with the seed is n efficient method for delivering smll mount of fertilizer. The N my be pplied in conjunction with other nutrients such s potssium, phosphorus, nd sulfur s strter fertilizer. Note, however, tht plcing fertilizer with the seed will dely emergence, sometimes by lmost week, nd in dry yers cn reduce the stnd. Do not pply more thn 25 lb N/ with the seed. 4

5 Phosphorus (P) Phosphorus fertilizer recommendtions in this publiction re bsed on the sodium bicrbonte P test nd do not pply to other test methods. This test is recommended throughout the western U.S. for lkline soils nd for soils tht hve recently become cidic. Test P only in the surfce foot of soil. The test cnnot be used to clculte the pounds of plnt-vilble P 2 O 5 /. Use Tble 2 to determine the recommended P fertilizer rte. A grin yield increse from P fertilizer ppliction is likely when soil test P is below 10 ppm. In fields with soil test P vlues of 11 to 20 ppm, yield my or my not increse from P fertilizer ppliction. In these instnces, yield increses from P fertiliztion seem to be ssocited with lte seeding dtes or root diseses tht limit plnt growth nd development. On-frm experiments re the best predictor of yield response to P fertilizer in this rnge of P soil test vlues. When soil test P vlues re greter thn 20 ppm, P fertilizer ppliction is not recommended. Fertilizer dditives Stndrd N nd P fertilizer mterils re mrketed with cotings to reduce voltile loss of mmoni (urese inhibitors), to stop or slow conversion of mmonium-n to nitrte-n (nitrifiction inhibitors), to increse vilbility of P, nd to protect fertilizer from leching loss (polymer cotings). Fertilizer dditives hve been mrketed for more thn 100 yers, nd nitrifiction inhibitors hve been common for 50 yers. All of these mterils dd to fertilizer cost. In most situtions, mngement cn ccomplish the sme result without purchsing the dditive. The question you need to nswer is, Is mngement more difficult or costly thn purchsing fertilizer dditive? Another pproch is to determine whether the reduction in nutrient loss chieved by n dditive will llow you to reduce fertilizer ppliction rtes sufficiently to py for the dditive. When considering whether to purchse fertilizer dditive, first identify the problem the dditive might solve, nd then consider whether you cn meet the sme gol with slight mngement chnge. For exmple, when ure fertilizer is pplied to the soil surfce nd not incorported, N my be lost through voltiliztion. Additives such s Agrotin, urese enzyme inhibitor, cn minimize mmoni loss. When ure remins on the soil surfce for more thn 24 to 48 hours, use of urese inhibitor my py for itself in reduced fertilizer cost (i.e., ppliction rtes cn be reduced). On the other hnd, incorportion of the fertilizer cn eliminte the need for the dditive. Another type of dditive, nitrifiction inhibitor, slows the conversion of mmonium-n to nitrte-n nd reduces the possibility of N loss by leching. Reserch to ssess the benefit of nitrifiction inhibitors ws conducted in soft white winter whet fields When P is recommended, pply P in bnd ner or with the seed t plnting. When bnd ppliction is not fesible, increse the P rte by t lest 50 percent. High ph nd fine-textured soils my require more P. Tble 2. Fertilizer bnded phosphorus (P) rte recommendtions using the sodium bicrbonte soil test. Soil test P b Apply this mount of P 2 O 5 (ppm) (lb/) Over 20 None Sodium bicrbonte soil test method. b If your frm or field hs demonstrted need for higher P rtes, use the P recommendtions from the Southern Idho Fertilizer Guide for Irrigted Winter Whet. ner Hermiston in Ure ws pplied t vrying rtes in single ppliction with nd without nitrifiction inhibitor, nd s split ppliction without the nitrifiction inhibitor. Whet yields rnged from 105 to 125 bu/. Among the tretments producing whet yields of 116 to 125 bu/, no sttisticlly significnt difference ws found for ppliction timing or use of n inhibitor (Tble 3). The most economicl option tht produced yield within this rnge ws spring ppliction of 200 lb ure/ in split pplictions (no inhibitor). This experiment shows tht when the timing of ure ppliction mtches the timing of whet N use, nitrifiction inhibitor is not beneficil or needed. Additionl experiments with whet nd other crops hve given similr results. Use of nitrifiction inhibitors or other fertilizer-enhncing mteril without considertion of your specific sitution cn result in dditionl expense without benefit. Tble 3. Soft winter whet yield, nitrogen (N) rte, ppliction timing, nd nitrifiction inhibitor (NI), Hermiston, Single Single Split with NI b w/o NI b w/o NI c N rte Whet yield (lb/) (bu/) e 107 de cde 118 bc bcd 115 bcde 125 b bcd 122 b b Yields followed by the sme letter re not sttisticlly different. b Single N ppliction pplied t Feekes 5. c Split pplictions pplied between Feekes 5 nd 9. 5

6 Potssium (K) Soil test K results nd the need for K fertilizer re often relted to crop rottion. When whet is plnted following pottoes, onions, or mny other vegetble crops, sufficient supply of K is usully vilble for whet growth, so no K ppliction is expected to be necessry before or t plnting. Low soil test K nd the need for K fertilizer re most likely when whet follows lflf or other forge crops. Whet uses bout the sme mount of K s N. However, unlike N, most of the K will be in the strw t hrvest. This fct is importnt for crops following whet. See the sidebr Nutrient removl nd recovery from strw for more informtion. A decision to fertilize with K should be bsed on soil test. Soil test K is n index of plnt K vilbility. K fertilizer recommendtions in this publiction re bsed on the sodium bicrbonte-extrctble K soil test. Soil smples tested for K using this soil test should be obtined from the surfce foot. Figure 2. Whet field ner hrvest. Most of the potssium (K) tken up by whet plnts will be in the strw t hrvest. Bling strw removes this K, depleting soil K for the next crop. Don Horneck, Oregon Stte University Nutrient removl nd recovery from strw The choice between bling or incorporting strw following hrvest will ffect nutrient vilbility for the following crop. Bling strw removes nutrients. The verge mount of N, P, K, nd S removed with grin nd strw for 150 bu/ yield is given in Tble 4. For this yield, grin contins 135 lb N/, nd strw contins 25 lb N/. Thus, 85 percent of the N is in the grin. In contrst, 75 percent of the K is in the strw. For this reson, bling strw removes substntil mount of K nd cn quickly decrese soil test K. K is esily removed from strw nd chff with rinfll or irrigtion. Thus, if strw is incorported, K is redily vilble to the next crop. Even when strw will be bled, however, the ese of K removl cn be exploited to retin K in the field. A single posthrvest irrigtion of t lest 0.25 inch of wter will remove substntil mount of K from strw tht is on the ground prior to windrowing. Irrigtion wter does not remove K from stnding stubble, however. Tble 4. Nutrient content for typicl soft white winter whet crop yielding 150 bu/. N P 2 O 5 K 2 O S (lb/) (lb/) (lb/) (lb/) Grin (150 bu) Strw (4.5 ton) Crop totl Nutrient content ws clculted using verge concentrtions from Tble 5 nd hrvest index of Tble 5 shows concentrtions of N, P, K, nd S in whet grin nd strw. These dt re from field experiments performed in western nd estern Oregon. Grin P, K, nd S vlues nd strw P vlues re more consistent thn re grin nd strw N nd strw K. The vribility from field to field nd yer to yer suggests tht you should use these dt only for informtion or s comprison to vlues mesured in your fields, rther thn s bsis for fertilizer ppliction rtes. In ddition to nutrient removl, strw hrvest gives rise to other concerns, such s soil helth nd soil orgnic mtter content. Tble 5. Grin protein concentrtion nd nutrient concentrtions in soft white winter whet grin nd strw from reserch in estern nd western Oregon. Protein N P K S (%) (%) (%) (%) (%) Grin Rnge Averge Strw Rnge Averge From 1981 through 2008, more thn 200 mesurements were mde for phosphorus, 100 for potssium, nd s few s 15 for sulfur. 6

7 Apply K fertilizer using the recommended rtes provided in Tble 6. A yield increse from K ppliction is likely when soil test K is below 75 ppm. In fields with soil test K vlues between 75 nd 100 ppm, yield response from K ppliction vries. On-frm experiments re the best predictor of yield response to K fertilizer in this rnge of soil test K vlues. K ppliction is not recommended when soil test K is greter thn 100 ppm. Potssium cn be brodcst pplied nd incorported before plnting, bnded t plnting, or pplied through irrigtion wter. If 30 lb K 2 O/ or less is to be pplied, K cn be bnded t plnting. Do not pply more thn 25 lb N/ in the bnd with K. If 60 to 100 lb K 2 O/ will be pplied, brodcst nd incorporte K fertilizer before plnting. Alterntively, K my be pplied through the irrigtion wter in the fll or in spring before jointing (Feekes 6, Figure 3). Tble 6. Fertilizer potssium (K) rte recommendtions using the sodium bicrbonte soil test. Soil test K Apply this mount of K 2 O (ppm) (lb/) Below Over 100 None Sodium bicrbonte soil test method. Sulfur (S) Excluding N, sulfur is the nutrient most likely to limit whet production. The S requirement of whet is bout 25 lb/. Sulfte-sulfur (SO 4 -S), the form of S vilble to plnts, is common in irrigtion wter. Unlike the mcronutrients (N, P, nd K), soil test for S in whet is not definitive. However, mesuring S in irrigtion wter nd soil will help determine the S fertilizer requirement. Low or moderte soil test vlues (below 10 ppm) re n indiction tht S ppliction my be wrrnted. A yield increse from S ppliction is likely if one or more of the following situtions pply: (1) whet is seeded lte in the fll, (2) greter-thnverge quntity of strw is present in the field, nd/or (3) the concentrtion of S in irrigtion wter is less thn 5 ppm. Field experience, observtion, nd on-frm experimenttion/experience re the best predictors of S fertilizer requirements. If S fertilizer is required, pply 10 to 30 lb S/. Sulfur cn be pplied s bnd t plnting nd cn be combined with other nutrients such s N in strter fertilizer. Alterntively, S cn be pplied with irrigtion wter before jointing (Feekes 6). Physiologic lef spot nd chloride deficiency Physiologic lef spot is ssocited with chloride (Cl-) deficiency, but it is not s common in irrigted whet s in drylnd situtions. In irrigted whet production, chloride is supplied by irrigtion wter or by murite of potsh (KCl) pplied to other crops in the rottion. A chloride ppliction should be considered only if physiologic lef spot hs previously been found in the field. Apply 100 lb KCl/ prior to flg lef emergence if physiologic lef spot hs been observed in the pst. Feekes growth or development stges Stge 1 one shoot Stge 2 tillering begins Tillering Stge 3 tillers formed Stge 4 lef sheths lengthen Stge 5 lef sheths strongly erected Figure 3. Growth stges in cerels. Micronutrients Appliction of the micronutrients boron, copper, mngnese, iron, molybdenum, or zinc does not routinely increse whet yield in estern Oregon. Most pplictions re the result of low soil test or previously observed deficiency symptom. Consider zinc (Zn) or boron (B) pplictions in the following situtions. Zinc: Appliction of Zn my be beneficil when DTPA-extrctble soil test vlues re less thn 0.8 ppm. Apply Zn t rte of 1 to 5 lb/. If pplying 1 to 2 lb Zn/, pply in bnd. Brodcst Zn if higher rtes re used. Boron: When soil test B is less thn 0.4 ppm, B need for whet cn be met with the ppliction of 0.5 to 2 lb B/. Growth stges in cerels Stem extension Heding Ripening Stge 10.5 Stge 11 flowering (whet) Stge 6 first node of stem visible Stge 7 second node visible Stge 8 lst lef just visible Stge 9 ligule of lst lef just visible Stge 10 in boot Stge

8 Spring nitrogen mngement Spring N pplictions re the most efficient wy to fertilize irrigted whet, regrdless of whether whet is plnted in fll or spring. In this section, we will consider when to pply N nd how much N to pply. See the sidebr N ppliction methods (pge 4) for informtion bout how to pply N. For more informtion bout the need for N for whet growth, see the sidebr Whet grin yield nd N supply. N timing (when to pply) Use plnt growth nd development not the clendr to determine N ppliction timing in spring. Whet growth nd development stges re illustrted in Figure 3 (pge 7). Through tillering (Feekes 5), whet ccumultes only smll mount of N (20 to 40 lb/). As jointing nd stem elongtion begin (Feekes 6), N is rpidly ccumulted by Whet grin yield nd N supply Whet yield is combintion of number of heds per unit re, kernels per hed, nd kernel weight. Both hed number nd kernels per hed re set erly in whet development (Feekes growth stges 2 through 5, Figure 3, pge 7). If whet follows pottoes or other vegetble crops, N ppliction is usully not needed t plnting. If whet follows crop leving little N in the soil, bnding 20 to 30 lb N/ t plnting supplies sufficient N for growth nd development through these stges. Nitrogen supply t jointing or stem elongtion (Feekes growth stge 6 or first node) is criticl for further plnt development nd optimum yield. Mximum N uptke occurs during this period of rpid growth nd continues until hed emergence (Feekes growth stge 10.1). Nitrogen stress during this period will reduce yield. Apply N fertilizer before jointing (Feekes growth stge 6) to optimize yield. Be creful not to overpply N t jointing, s lodging redily results. Clendr dte is not relible predictor of jointing, becuse temperture (ccumulting het units) controls whet development. The dte of jointing will vry by vriety, plnting dte, spring tempertures, nd growing conditions. In estern Oregon, jointing typiclly occurs between Mrch nd April. Annul spring temperture vribility cn cuse jointing to begin in erly Februry or s lte s erly My. A degree-dy clcultor is vilble t Kernel weight is determined by the mount of N present in the plnt nd, to lesser degree, the N present in the soil t hed emergence (Feekes growth stges ). the plnt. In 5- to 8-week period (Feekes 5 10), whet tkes up 100 to 150 lb N/, with pek N uptke rte of 2 to 3 lb N//dy during stem elongtion (Figure 4). By the boot stge (Feekes 10), the plnt hs ccumulted the mjority of its N for the seson, but only bout hlf its biomss (Figure 4). As whet begins to mture nd grin formtion begins, N is trnslocted from the leves nd stems to the grin hed. Spring N my be pplied incrementlly with irrigtion wter. In generl, ppliction of N should be completed prior to jointing (Feekes 6), when rpid N uptke begins. Tke cre to ensure tht dequte N is vilble during stem elongtion (Feekes 6 9). Whet yield is reduced when N is limited or unvilble during this period. Whet will not produce much dditionl yield when fertilized t or fter the ppernce of the flg lef (Feekes 8). Lte-seson N fertiliztion will increse grin protein n undesirble effect in soft white whet. In ddition, lte-seson N fertiliztion increses the risk of N loss to the environment. Cumultive biomss (t/) Cumultive N uptke (lb/) N uptke (lb//dy) jointing boot nthesis ripening Dys fter spring N ppliction Figure 4. Typicl biomss ccumultion nd nitrogen (N) uptke for whet. Dt from one growing seson. 8

9 N rte (how much to pply) Irrigted soft white winter nd spring whet requires 275 to 300 lb N/ to produce optimum yield when rooting depth is dequte nd sufficient irrigtion wter is supplied. Grin yields pproching 200 bu/ hve been produced with this mount of N. Nitrogen is supplied by the soil, decomposing crop residue, nd fertilizer. Unless no vilble N is present in the soil ( highly unlikely sitution!), ppliction rtes of N fertilizer do not need to be this high. To determine the mount of fertilizer N to pply in the spring, you need to mesure the mount of plnt-vilble N in the root zone. To mesure plnt-vilble N, collect soil smples for lbortory nlysis. For spring whet, soil smples cn be collected before plnting. For winter whet, collect smples fter winter dormncy, but erly enough to llow for soil nlysis nd fertilizer ppliction before jointing. Collect smples from the effective root zone (usully 2 to 3 feet) in 1-foot increments nd hve them nlyzed for nitrte-n (NO 3 -N). Irrigtion mngement influences rooting depth. Frequent, smll wter dditions will result in whet plnts with shllow roots, typiclly round 2 feet deep. Drylnd or deficit-irrigted systems, on the other hnd, encourge deeper rooting, typiclly 4 to 5 feet. Thus, where whet is deficit irrigted, smpling should extend to 4 or 5 feet. Smples from the surfce foot should lso be nlyzed for mmonium N (NH 4 -N). Sum nitrte from ll depths nd mmonium N from the top foot to determine totl plnt-vilble N (see Tble 7). Decomposing residue from crops such s pottoes nd lflf will contribute N to the whet crop. In contrst, residue from grin crops, such s whet or corn, requires N for decomposition. As soil microbes decompose these residues, they cn tke N from the current whet crop. Typicl residue scenrios include the following: Nitrogen from potto residue becomes vilble rpidly in the fll nd is lmost completely vilble by Jnury 1. This N cn be mesured in spring soil test. Alflf killed in the fll will not decompose sufficiently by spring for the N to be mesured in spring soil test. Additionl N will become vilble during the growing seson s lflf residues decompose. Grss seed residue incorported fter hrvest begins decomposing immeditely fter incorportion, providing plnt-vilble N for the whet crop. Most of the N from decomposing grss seed residue becomes vilble by lte winter nd cn be mesured in spring soil test. Use Tble 9 (pge 10) to determine the recommended spring N rte, bsed on results of the spring soil test (totl plnt-vilble N) nd the previous crop. Tble 9 tkes into ccount the effect tht decomposing crop residues hve on plnt-vilble N. The effectiveness nd dequcy of N ppliction cn be tested with posthrvest grin protein nlysis. Use this nlysis to djust mngement in future whet crops bsed on experience from previous crops. See Posthrvest nutrient considertions for detils (pge 10). Folir nutrient ppliction Folir nutrient ppliction is dvocted for some crops in certin situtions: when roots re dmged, yield potentil is high, or high soil ph limits vilbility of micronutrients. However, folir ppliction of fertilizer to soft white whet in Oregon is not supported by reserch in ny of these situtions. Folir fertilizer use in whet hs not incresed whet yield nd sometimes results in decresed yield (Tble 8). Nitrogen nd zinc were pplied to whet folige in three fields during April. Even where whet yield ws 120 bu/ (Field 3), the folir nutrient ppliction did not increse yield. Whet yield lso ws not incresed by folir fertilizer ppliction when yield ws low due to infection by tke-ll root rot (Field 1). Tble 8. Whet grin yield with folir ppliction of nitrogen (N) nd zinc (Zn) compred to grin yield without folir nutrient ppliction, Field 1 Field 2 Field 3 Rte Grin yield Mteril (lb/) Dte (bu/) None N+Zn 1 pt/ April N+Zn 2 pt/ April Tble 7. Exmple of plnt-vilble nitrogen (N) for smples collected in 1-foot increments when the rooting depth is 3 feet. Ammonium-N Nitrte-N Plnt-vilble N Soil depth (NH 4 -N) (NO 3 -N) (NH 4 -N + NO 3 -N) (inches) (lb/) (lb/) (lb/) Totl plnt-vilble N

10 Tble 9. Recommended spring nitrogen (N) ppliction rtes for fll- or spring-seeded whet bsed on previous crop nd totl plnt-vilble N. Totl plnt-vilble N (lb/) Previous Recommended spring N rte crop (lb/),b Pottoes, onions, nd other vegetbles c Alflf d Other legumes e Grin f N rtes in this tble re suitble for n expected yield of 140 bu/ or higher. Where yields typiclly re lower (e.g., Mlheur County), where N is supplied through irrigtion wter, or where experience hs shown tht lower N rtes re needed, use the N recommendtions from the Southern Idho Fertilizer Guide for Irrigted Winter Whet. b If N ws pplied in the fll, subtrct the mount of pplied N from the vlues below. c Avilble N fter potto crop typiclly is 100 to 300 lb/. If less thn 100 lb N/ is mesured in spring soil smple fter potto crop, review your mngement prctices nd smpling procedure. d Assumes helthy stnd nd 6 inches of regrowth before incorportion or killing. e Increse the spring N rte if pe vines (hy) re removed from the field. f Whet, brley, ots, or corn s previous crop when stover or strw is incorported. Posthrvest nutrient considertions Evlution of N Nutrient mngement for whet does not stop t hrvest. Growers routinely receive grin protein dt t the time of sle. This dt cn be used s report crd to check N fertilizer dequcy, s shown in Tble 10. Tble 10. Grin protein s report crd for nitrogen (N) mngement of soft white whet. Grin protein (%) N supply for seson ws: Below 8 Indequte On trget Over 10.5 Excess (or yield ws limited by nother fctor) Yield should be t lest 80 bu/ to use this tble. Mximum economic yield of soft white whet is ssocited with grin protein concentrtions between 8.0 nd 10.5 percent. Consider the following guidelines. Grin protein levels less thn 8.5 percent suggest tht N ws indequte nd tht dditionl N fertilizer would hve incresed yield. Grin protein levels greter thn 10.5 percent suggest tht N ws excessive or tht yield ws limited by fctor other thn N. Irrigted whet yields cn be limited by vriety of problems, such s disese, irrigtion timing or mount, insect infesttion, insufficient nutrients, poor nutrient timing, or weed competition. If grin yield ws ner expecttions nd grin protein ws bove 10.5 percent, then excess N rther thn yield limittion ws the cuse of the high grin protein. Crefully evlute N ppliction rte, timing, nd soil test vlues for future whet crops. For more informtion Ayers, R.S. nd D.W. Westcot Wter Qulity for Agriculture. Food nd Agriculture Orgniztion of the United Ntions. Irrigtion nd Dringe Pper No. 29, Rev. 1, Rome. Monitoring Soil Nutrients Using Mngement Unit Approch, PNW ctlog/pdf/pnw/pnw570-e.pdf Slt-ffected Soils for Crop Production, PNW 601-E. pnw601-e Southern Idho Fertilizer Guide for Irrigted Winter Whet. CIS0373.pdf Check with your locl experiment sttion for pertinent whet trils Oregon Stte University. This publiction my be photocopied or reprinted in its entirety for noncommercil purposes. This publiction ws produced nd distributed in furthernce of the Acts of Congress of My 8 nd June 30, Extension work is coopertive progrm of Oregon Stte University, the U.S. Deprtment of Agriculture, nd Oregon counties. Oregon Stte University Extension Service offers eductionl progrms, ctivities, nd mterils without discrimintion bsed on ge, color, disbility, gender identity or expression, mritl sttus, ntionl origin, rce, religion, sex, sexul orienttion, or vetern s sttus. Oregon Stte University Extension Service is n Equl Opportunity Employer. Published December 2010.