New N Management Strategy: Oklahoma

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

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Address Temporal and Spatial Variability
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Temporal variability

• Uncertain yield potential

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Temporal variability

• Uncertain use (availability) of non-fertilizer N

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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
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Temporal variability (N Response RI)
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Solutions

• Estimate N response in-season.

RINDVI 1.46
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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 (YP0RI) 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 (GDDgt0)
YP0
Planting date
NDVI (sensing date)
November
March
June
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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
GDDgt0)YPN YP0 RIFertilizer N (Grain N
uptake at YPN Grain N uptake at YP0)/0.7
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Solutions

• Provide in-season estimate of yield (INSEY)

In-SeasonEstimatedYield (INSEY)
NDVI at F5

days from planting to F5, GDDgt0
Good predictor of final grain yieldRequires
only one sensor readingWork over different
regions/biotypes
Units N uptake, kg ha-1 day-1 where GDDgt0
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Spatial variability
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Solutions

• Measure and treat spatial variability

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Solutions

• Measure and treat spatial variability, in-season

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Solutions

• Measure and treat spatial variability, in-season

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Solutions

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

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Solutions
Must have Qualified Engineer to fix what
Agronomy Personnel tear up
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Economic estimates
Average Gain 17.13/acre/yr
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2002 Field trials

• 10 trials using 60-ft boom sensor-applicator.

• Web site.
• http//www.dasnr.okstate.edu/nitrogen_use/

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Hand-held Farm ScaleSpring Wheat Mexico, Ecuador
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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)