On-Farm Trials Using a Field-Scale, One Meter Resolution Variable Nitrogen Rate Applicator

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On-Farm Trials Using a Field-Scale, One Meter
Resolution Variable Nitrogen Rate Applicator
precision SENSING
Oklahoma State University
Ukiah, CA Stillwater, OK
J. Mayfield. T. MayfieldS. Reed, K. Diebold, C.
Washmon

• K.W. Freeman, R.W. Mullen, G.V. Johnson, M.L.
  Stone, J.B. Solie, R.Teal, P. Hodgen, M.
  Humphreys, J. Mosali,S. Moges, K. Brixey, and
  W.R. Raun

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Field Scale VRT Applicator
Video
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Hand-Held Sensors
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Spatial Scale
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Boman et al., 1995 (Winter Wheat)

• Advantages of mid-season N application (versus
  preplant)
• Midseason N delayed to March not advantageous

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Aug 16, 2002
Aug 28, 2002
Nov 7, 2002
days from planting to sensing
Predicted yieldwith no added Nfertilization
Planting date
NDVI (sensing date)
November
March
June
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Tom Cannon Farm, Blackwell, OK (April 11, 2002)
Response Index NDVI (N-Rich Strip) (117
kg/ha) 0.8
NDVI Farmer Check (50 kg/ha) 0.6
RI 0.8/0.6 1.33
N-Rich Strip
Kenneth Failes, Cherokee, OK (March 20, 2002)
RI 0.60/0.57 1.1
Farmer Check
N-Rich Strip
Farmer Check
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• Strong correlation between RINDVI (vegetative
  stages) and RI HARVEST
• Accurately predict the crops ability to respond
  to N
• RINDVI may refine whether or not N should be
  applied, and how much

Check
N-Rich Strip
NDVI 0.83
NDVI 0.62
RINDVI 0.83/0.62 1.34
2500 kg/ha
1900 kg/ha
RIHarvest 2500/1900 1.32
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Variable Response Index
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Aug 16, 2002
Aug 28, 2002
Nov 7, 2002
Predicted yieldwith N fertilization
days from planting to sensing
Predicted yieldwith no added Nfertilization
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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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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YPMAX
YP0
YPN (RI2.0)
YPN (RI1.5)
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Response Index vs. Sufficiency
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Steinert-Peters
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Marshall-Hennessey
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Claybaker-Blackwell
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All 10 Sites
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Conclusions

• Sensor-based variable N rates were evaluated at
  the farm scale (every 0.4m2).
• Ten farmer fields were identified and fertilized
  using the OSU/N-Tech variable N rate applicator.
  
• Grain yields averaged 2.7 Mg/ha when each 0.4m2
  were fertilized using VRT.
• At the same average N rate as that employed with
  VRT (flat rate), grain yields averaged 2.4 Mg/ha.
  
• Increased yields at decreased rates were in part
  due to recognition and treatment of small-scale
  spatial variability.

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www.dasnr.okstate.edu/nitrogen_use
Ukiah, CA Stillwater, OK
www.ntechindustries.com
precision SENSING
Oklahoma State University