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Mdule 2: Nitrgen Management Intrductin Nitrgen (N) is essential fr plant grwth: part f every living cell cmpnent f all amin acids (prteins and enzymes) and nucleic acids cmpnent f chlrphyll Nitrgen deficiency in plants appears as chlrsis r yellwing mainly in lder leaves (mbile nutrient). Nitrgen nutritin affects yield, but als crp quality. Nitrgen has interactin implicatins with efficient use f ther nutrients.
Mdule 2: Nitrgen Management Basic Nitrgen Prcesses in the Sil-Plant System Nitrgen sil prcesses Mineralizatin: rganic N cnversin t NH + 4 Nitrificatin: NH 4+ cnversin t NO - 3 Immbilizatin: inrganic N cnversin t rganic N Nitrgen gains Bilgical N fixatin: plant-micrbe symbitic supply f plant available N Fertilizatin: supplements sil plant-available N Organic additins: increases rganic matter and ptentially plant-available N Nitrgen lsses Crp remval: reductin in sil N with crp harvest Leaching: NO 3- lss with water drainage and ptential water quality issues Denitrificatin: NO 3- lss by micrbial cnversin t N gases with ptential air quality issues Vlatilizatin: ammnia lss frm sil surface with ptential air quality issues Ersin: rganic matter lss with water runff and ptential water quality issues
Mdule 2: Nitrgen Management The Nitrgen Cycle in Agrecsystems Frm Rthamsted Research, www.rthamsted.ac.uk
Mdule 2: Nitrgen Management Nitrgen Fertilizatin Rate Determinatin and Ecnmic Respnse 200 Crn Yield (bu/acre) 150 100 50 Crn Fllwing Crn Crn Fllwing Sybean Ecnmic ptimum N rate Agrnmic maximum N rate 0 0 50 100 150 200 250 N Rate (lb/acre) Nitrgen rate respnse f crn fllwing crn and crn fllwing sybean in Iwa. J.E. Sawyer, Iwa State University.
Mdule 2: Nitrgen Management Nitrgen Rate: Ecnmic and Envirnmental Issues Applying mre than enugh N is nt envirnmentally safe r cheap insurance. Farmers need t critically determine N rates because f: High N fertilizer csts Ptential ecnmic lss Envirnmental impacts
Mdule 2: Nitrgen Management Nitrgen Fertilizatin Rate Determinatin and Ecnmic Respnse Net Return t N ($/acre) Ecnmic Optimum Nutrient Rate Net Return t N Nitrate-N Subsurface Tile Nitrate-N (mg/l) Nutrient Rate Imprtance f using ptimum N rates fr greatest prfit and minimizing nitrate-n lss (via subsurface tile drainage).
Mdule 2: Nitrgen Management Rate Determinatin and Ecnmic Respnse Nitrgen recmmendatins have been based n yield-gals fr many years in the Midwest USA and ther regins. Expected crp yield is the criterin fr determining N rates. In the Midwest USA there is pr crrelatin between site-year crp yield and ecnmic ptimum N rate. Use a new apprach with N respnse data-driven recmmendatins sensitive t measured N respnse and N and grain prices. In the Midwest USA called the MRTN (Maximum Return T N).
Mdule 2: Nitrgen Management Nitrgen Rate Determinatin and Ecnmic Respnse 300 Optimum N Rate (lb/acre) 250 200 150 100 50 0 0 50 100 150 200 250 300 Grain Yield (bu/acre) Relatinship between the ecnmic ptimum N rate and crn grain yield level. Data frm crn after sybean in Iwa. J.E. Sawyer, Iwa State University.
Mdule 2: Nitrgen Management Nitrgen Diagnstic Methds: Pre-plant and Pre-sidedress Sil Sampling N rate t Apply (lb/acre) Pre Plant (lb/acre) r Pre Sidedress N Test (mg/kg) General relatinship between N fertilizatin rate and preplant r pre-sidedress sil nitrate-n cntent.
Mdule 2: Nitrgen Management Nitrgen Diagnstic Methds: Chlrphyll Meter and Crp Canpy Sensrs Relative Chlrphyll Meter r Relative Sensr Values 1.0 0.8 0.6 0.4 0.2 0.0 Deficit 0 Excess N Rate Difference frm Ecnmic Rate Relative crp canpy sensr value as related t the differential frm the ecnmic ptimum N rate in crn.
Mdule 2: Nitrgen Management Nitrgen Variable Rate Technlgy Sils differ within fields and that can result in significant yield variatin. Fields are divided int management units where the fertilizer applicatin may differ. Diagnstic tls fr N VRT intensive sil sampling sil and crp remte sensing aerial images yield mapping crp mdeling
Mdule 2: Nitrgen Management Nitrgen Applicatin Timing The demand fr N by a crp is assciated with the grwth rate. Ultimate gal f N management is t time N fertilizer applicatins t match crp uptake needs. Applicatin timing can play a critical rle in ptimizing N use efficiency. Fall N applicatin increases risk f lss. Nitrificatin inhibitrs with fall-applied N can imprve effectiveness where fall applicatin is an acceptable practice.
Mdule 2: Nitrgen Management Nitrgen Applicatin Timing Spring applied N is generally mre effective than fall applicatin. Fall applicatin is nly suggested fr regins where: winters have frzen sils rainfall is lw sils withut excessive drainage Benefits frm sidedress and split N applicatins are greatest where there is a high risk f N lss between preplant timing and crp N use. Sidedress als allws fr use f in-seasn sil tests and plant N stress sensing. Yield reductins due t delayed applicatins can be minimized by applying sme N at planting.
Mdule 2: Nitrgen Management Nitrgen Surces Manure Mix f rganic and inrganic N frms Liquid r slid typically with lw nutrient cncentratin Sampling and labratry analysis are always recmmended Significant time may be needed t prvide plant available inrganic N Anhydrus ammnia (NH 3 ) (82 % N) Relative lw cst and high N cncentratin Care shuld be taken when transprting and applying It can be applied pre-plant r sidedressed in rw crps Sil misture cntent shuld nt be t dry r t wet Shallw placement may result in early seasn crp seedling r rt damage Fr small grains, knife spacing needs t be clse enugh t avid deficient strips Additin f a nitrificatin inhibitr with late fall applicatin may be beneficial
Mdule 2: Nitrgen Management Nitrgen Surces Urea (CO(NH 2 ) 2 ) (46 % N) It cnverts quickly t ammnium In n-till, ammnia vlatilizatin frm surface applicatin is a cncern A urease inhibitr can help reduce vlatile lss with surface placement Urea-ammnium nitrate slutin (UAN) (28-32 % N) Widely used as a bradcast and injected prduct It can be banded n the sil surface which reduces vlatilizatin Ammnium nitrate (NH 4 -NO 3- ) (34 % N) Bth N prtins are immediately available fr plants There is n vlatile lss ptential frm surface applicatin n mst sils It s use has been decreased due t safety regulatins (explsive) Slw and cntrlled release N surces Prducts with varying chemical structures that slw cnversin r release timing f plant available N
Mdule 2: Nitrgen Management Nitrgen Applicatin Placement Injected r banded T avid vlatile lsses and drs T match crp rw spacing T avid crp injury that may ccur with bradcast T have a high N starter available fr early grwth Bradcast Unifrm distributin f N acrss the sil Often applied pre-plant r prir t emergence After crp emergence can cause crp injury with sme prducts Fertigatin It allws fr multiple applicatins thrughut the seasn Especially useful n carse textured sils Timely rains may reduce the need fr irrigatin
Mdule 2: Nitrgen Management Management Practices fr Nitrgen Fertilizatin Management practice cncepts t help address P use fr the right nutrient surce, at the right applicatin rate and time, and in the right place Rate Selecting the apprpriate N rate is highly imprtant fr achieving ecnmic and envirnmental gals. Recmmended rates shuld be based n research-derived respnses t N applicatin. Sil preplant and presidedress testing fr nitrate can be used t adjust applicatin rates. Plant sensing tls are used t access cereal crp N stress and adjust in-seasn N rates. Nitrgen rates shuld be specific fr the crp rtatin and previus crps.
Mdule 2: Nitrgen Management Management Practices fr Nitrgen Fertilizatin Surce Many N fertilizers and manures can be used successfully if management is crrect fr the surce. In situatins with high prbability fr N lss, cntrlled release fertilizers can avid lss by physically prtecting applied N. Placement Nitrgen placement shuld be ptimal fr plant uptake and avidance f vlatile lss. In dry cnditins, N placed within the rt zne can enhance crp uptake. Nitrgen applicatin with irrigatin can be useful t supply N during crp N uptake.
Mdule 2: Nitrgen Management Management Practices fr Nitrgen Fertilizatin Timing Maximizing crp N uptake reduces ptential fr lss. N applicatin timed with crp uptake increases nutrient use efficiency Spring applicatin is generally mre effective than fall. Nitrificatin inhibitrs can slw cnversin f fall-applied anhydrus ammnia. Yield reductins due t delayed sidedress applicatins can be minimized by applying sme N at planting. In seasn N applicatins can avid lss cnditins that may ccur befre planting.
Mdule 2: Nitrgen Management Summary Prper N management is essential fr many reasns: t supplement sil N supply in rder t meet crp needs t ptimize crp prductin and prfitability t imprve N use efficiency t reduce impacts f N n air and water quality t avid increased regulatin Nitrgen management is mre cmplex in humid regins than in drier areas. Nitrgen management gals: apply N at ptimal ecnmic rates select an applicatin timing t minimize N leaching and denitrificatin use diagnstic tls t aid in rate determinatin and adjustment use the apprpriate N surce and placement fr each prductin system use precisin agriculture technlgies when apprpriate