2015 GRDC Topdressing for Irrigators. Rob Norton - PDF document

2015 GRDC Topdressing for Irrigators. Rob Norton http://anz.ipni.net @ANZIPNI Finley, Monday August 10, 2015. 4R Nutrient Stewardship • The 4Rs are the foundation Rate and guiding principles of Source nutrient BMPs (Roberts 2007) Place Time • Approach is simple … apply the correct nutrient in the amount needed, timed, and placed to meet crop demand The 4R’s is both: • a process (what needs to be considered) and • an outcome (how the pieces fit together) http://anz.ipni.net The ¡basic ¡scien+fic ¡principles ¡of ¡managing ¡crop ¡ nutrients ¡are ¡universal ¡ ¡ 1. Appropriately assess soil nutrient supply 1. Supply in plant available forms 2. Assess all available 2. Suit soil properties indigenous nutrient sources 3. Recognize synergisms among 3. Assess plant demand elements 4. Predict fertilizer use efficiency 4. Blend compatibility Rate Source Place Time 1. Recognize root-soil dynamics 1. Assess timing of crop uptake 2. Assess dynamics of soil nutrient 2. Manage spatial variability 3. Fit needs of tillage system supply 4. Limit potential off-field 3. Recognize timing of weather factors transport 4. Evaluate logistics of operations 1

Right source, rate, time, and place • science-based principles • not static • Interdependent & applied in cropping systems • The 4Rs provide flexibility to nutrient management recognizing that FBMPs are site and crop specific depending on soils, climatic conditions, crop and cropping history, and management expertise, • Ignorance ¡more ¡frequently ¡ and can be applied in large-scale, begets ¡confidence ¡than ¡ extensive agriculture or small family does ¡knowledge. ¡ farms. – Charles ¡Darwin ¡ The 4R Nitrogen Quiz 12 Questions to ponder: • The 4 R’s of nutrient • How much N can a crop take up stewardship mean? through its leaves? • How do I know if the crop needs • How does canola N demand more N? differ from wheat? • What is the urea equivalent of • What else can go wrong #1 1m 3 of broiler litter? • What else can go wrong #2 • Which is the most important N • What else can go wrong #3 loss pathway? • What can we do something • N fertilizers contribute to soil about? acidification by what process? • When is it too late to apply N Rate Source Place Time 2

System changes & responses Source/Rate/Place combinations Rate • Right Place 20 ¡cm ¡ ¡ 30 ¡cm ¡ Source Place 125 ¡mm ¡Share ¡ 33 ¡ 22 ¡ Time Spear ¡Point ¡ 13 ¡ 8 ¡ • Maximum urea (kg N) rates Crop ¡ Soil ¡ SBU ¡% ¡ 8% ¡ 17% ¡ 25% ¡ 33% ¡ Cereal ¡ Light ¡ 15 ¡ 20 ¡ 25 ¡ 30 ¡ Medium ¡ 20 ¡ 30 ¡ 35 ¡ 40 ¡ Canola ¡ Light ¡ 0 ¡ 10 ¡ 15 ¡ 20 ¡ Medium ¡ 5 ¡ 15 ¡ 20 ¡ 30 ¡ • Worst Case – Canola, Light Soil, Urea/MOP, low SBU • Best Case – Cereals, heavy soil, Super/MAP, high SBU http://seed-damage-calculator.herokuapp.com 3

N deficiency in wheat Read the crop … . N-rich strips? Shoot numbers = no per square meter - tillers and main stems good measure of integrated N supply up until DC30 Target shoot numbers = rainfall+mm irrigation = 400+200 = 600/m 2 1.2 1 0.8 0.6 0.4 0.2 0 -0.2 0 200 400 600 800 1000 -0.4 -0.6 -0.8 4

N content of typical fertilizers • Types Name %N Kg product to supply – N as nitrate 50 kg N – N as ammonium Urea 46% 109 – N as amide UAN 42% w/v 118 l – N as organic AmSul 21% 238 Poultry Litter ~2.5% dwt 3 m 3 • Content to application Amm Nitr 34% 147 Application Rate (kg prod/ha) Pot Nitrate 13% 385 MAP 10% 500 = 100*kg N/%N Anhydrous 82% 61 eg Urea = 100*50/46 Litter – age, density, moisture content = 109 N losses – enhanced efficiency fertilizers • Immobilization – high C soils Nitrification inhibitor • Leaching Polymer coating – Light soils, wet. • Denitrification – High C, wet soils • Volatilization – Surface ammonium sources. Urease inhibitor 5

How Nitrogen affects soil acidity • Nitrification - H + is released during the conversion of NH 4 + to NO 3 - • Leaching - NO 3 - carries basic ions with it. They are replaced by H + + H NH 4 + • Ammonium fertilizers and acidity - NO 3 N Source Lime Eq. Kg Lime/ (kg lime/ kg kg N) fertilizer AmS 6 1.15 MAP 6 0.67 DAP 4 0.63 Urea 2 0.92 Pot Nit 0 0 Intervention Options GRDC – N timing*form*rate 2013 Trial Locations 0, 25, 50 kg/ha N DC32, DC39, DC55, DC70 UAN, GrUrea, SUrea. 8 sites across HRZ, report on 3 from Victoria SFS – Jon Midwood, HRZ Regional Cropping Solutions Network. Effect of timing – mean of all sites, rate and source. Time% Yield% Protein% N%Rem% Weights% Screens% % DC32% 5.54% 9.9% 97% 76% 7.8% DC39% 5.43% 9.9% 95% 75% 7.2% DC55% 5.33% 10.3% 97% 76% 7.2% DC70% 5.07% 9.8% 88% 75% 7.3% Sign% **% **% **% ns% ns% % Early N = Yield – window is from DC32 to DC39 Late N = Protein – window s DC55 but before DC70 6

Foliar, soil or what?? • N is taken up through the leaves – Urea > ammonium > nitrate • Limited by either urea toxicity, salt burn or leaf area. • Timing is important • Worst effect if flag leaf is damaged • Foliar uptake probably 10-15 kg N/ ha • Rest is taken up through roots. • Leaf and soil – amm. loss. ! ! Canola! Wheat! Removal? ! Mean!seed! Removal!in!a!! Mean!seed! Removal!in!a! content! 2.0!t/ha! content! 3.0!t/ha! @8%!MC! @10%MC! N! 4.28%! 79!kg! 2.33%! 62!kg! • N ~ 25%+ P! 5672!! 10.4!kg! 3329!! 9.0!kg! K! 6863!! 12.6!kg! 4606!! 12.4!kg! • P ~ 10%+ S! 4062!! 7.5!kg! 1742!! 4.7!kg! B! 12.0!! 22!g! 2.2!! 6!g! Cu! 2.9!!! 5!g! 4.8!! 13!g! • S ~ twice Zn! 37.9!! 70!g! 23.0!! 62!g! Mn! 38.0!! 70!g! 43.5!! 117!g! • B ~ four fold • Micros – more efficient that wheat – N budget = 80 kg N/t reasonable for canola Rate Source Place Time Canola and N – old variety. 4 waterings Taylor et al. 1991, Kyabram 5.00 Mean of 2 years data 48.0 4.50 47.0 4.00 46.0 3.50 45.0 3.00 44.0 2.50 43.0 2.00 42.0 1.50 41.0 1.00 40.0 0.50 39.0 0.00 38.0 0N 50N 100N 200N Rainfed Yield Irrigated Yield Rainfed Oil Irrigated Oil 7

Timing? g/plant Change N supply Continue 55 DAS 90 DAS • Early N 7 3.1 68 49 – Wheat 40 kg by GS30 210 69 14 60 – Canola 40 kg by SE Hocking 1987 • Rapid N SE to FF – Wheat and Canola 4.5 – Ability to compensate 4 3.5 • Canola continues N uptake 3 – With added water 2.5 Rainfed 2 – Terminated by temps >32 o C Irrigated 1.5 1 Rate 0.5 Source 0 100N 20/80N 50/50N Place Time What don’t you know? • Knowns & Should be Known – What N is there & is it accessible • Soil test / Soil guess (root depth). – Rough yield estimate/target. • Known Unknowns – Plus - Soil mineralisation in-crop. – Minus - Losses of soil & applied N. – How much supplied ends up in the grain. – Improved yield estimate as season unfolds. • Unknowns – Frost, bugs, late heat. – Operation successful – but the patient died 8

So who do you call? http://www.extensionaus.com.au/category/field-crop-nutrition Also ask through twitter #AuCropNutrition 9

Understanding crop nutrition • You get nothing for nothing • Identify the limiting factor • There are no silver bullets. Some take aways • There is no one N solution – 4R’s approach • Invest in N between DC31 and DC55 as yield is king • Late N to change grades is an option but luck is needed. • Canola is different to wheat – yield response later. • There would need to be compelling circumstances to justify moving away from top-dressed urea, provided as the season unfolds. • There is still a risk due to season. 10