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New N Management Strategy: Oklahoma

New N Management Strategy: Oklahoma. G. V. Johnson, W. R. Raun, J.B. Solie, and M.L. Stone Oklahoma State University Stillwater, OK. Poor NUE. Poor NUE. Result of mineral N present at concentrations in excess of plant needs. Soil-Plant system leaks in proportion to excess mineral N.

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New N Management Strategy: Oklahoma

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  1. New N Management Strategy: Oklahoma G. V. Johnson, W. R. Raun, J.B. Solie, and M.L. Stone Oklahoma State University Stillwater, OK

  2. Poor NUE

  3. Poor NUE • Result of mineral N present at concentrations in excess of plant needs. • Soil-Plant system leaks in proportion to excess mineral N. • Excess N = f (yield potential, supply of non-fertilizer N. • Typically, all fertilizer-N applied before crop needs any (sometimes even applied six months in advance).

  4. Address Temporal and Spatial Variability

  5. Temporal variability • Uncertain yield potential

  6. Temporal variability • Uncertain use (availability) of non-fertilizer N

  7. Temporal variability • Extent to which yield potential and non-fertilizer N supply determine fertilizer-N response given by: • Yield potential with N___ Yield potential without N = Response Index

  8. Winter wheat RI • Range = 1.0 to 4.1 • Mean = 1.9 • CV = 38 • Irrigated corn RI • Range = 1.1 to 3.5 • Mean = 1.8 • CV = 34 Temporal variability (N Response; RI)

  9. 90 N Preplant 45 N Preplant Solutions • Estimate N response in-season. RINDVI = 1.46

  10. WINTER Wheat NFOA Aug 16, 2002 1. Establish preplant N Rich Strip(NRS) 4. Determine Response Index (RI)2. NDVI (biomass), Feekes 4-6 =NDVINRS/NDVIFarmer3. Predict potential yield (each 0.4m2) 5. Predict potential grain yield need # of days from planting to (YP0) with added N, YPN =(YP0*RI) sensing (INSEY = biomass prod./day) 6. Fertilizer Rec = (grain N uptake INSEY vs. Yld eqn. YPN – grain N uptake YP0/0.7) YPN RI days from planting to sensing (GDD>0) YP0 Planting date NDVI (sensing date) November March June

  11. Kenneth Failes, Cherokee, OK (March 20, 2002) RI = 0.60/0.57 = 1.1 Predicted yieldwith N fertilization(YPN) RI N-Rich Strip days from planting to sensing Predicted yieldwith no added Nfertilization (YP0) Planting date Farmer Check NDVI (sensing date) INSEY = (NDVI/days from planting to sensing where GDD>0)YPN = YP0 * RIFertilizer N = (Grain N uptake at YPN – Grain N uptake at YP0)/0.7

  12. Solutions In-SeasonEstimatedYield (INSEY) NDVI at F5 = days from planting to F5, GDD>0 • Provide in-season estimate of yield (INSEY) +Good predictor of final grain yield+Requires only one sensor reading+Work over different regions/biotypes Units: N uptake, kg ha-1 day-1 where GDD>0

  13. Spatial variability

  14. Solutions • Measure and treat spatial variability

  15. Solutions • Measure and treat spatial variability, in-season

  16. Solutions • Measure and treat spatial variability, in-season

  17. Solutions • Measure and treat spatial variability, in-season • Apply most N topdress

  18. Solutions Must have “Qualified Engineer” to fix what “Agronomy Personnel” tear up

  19. Economic estimates Average Gain = $17.13/acre/yr

  20. Topdress N Return ($/Ac) Obs. Treatment Preplant N Early Late Total N Yld (bu/a) 81 VRT 41 15 23 79 39.8 100 17 Farmer Check 52 21 20 92 34.6 82 2002 Field trials • 10 trials using 60-ft boom sensor-applicator. • Web site. • http://www.dasnr.okstate.edu/nitrogen_use/

  21. Hand-held Farm ScaleSpring Wheat Mexico, Ecuador

  22. Procedure Output: Potential yield without N, potential yield with N, N fertilizer needed (1) NDVI collected from NRich Strip & Farmer Practice Enter: Max Yield for areaPlanting date, sensing date, NDVI values from (1)

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