Using Remote Sensing to Characterize Yield Loss due to Water and N stress in Corn.

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Using Remote Sensing to Characterize Yield Loss
due to Water and N stress in Corn.

• David E. Clay, K. Kim, J. Chang, S.A. Clay, C.G.
  Carlson, and K. Dalsted

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N and water stress

• NASA
• North Central Soybean Board
• SD Corn Utilization Council
• USDA-CSREES
• PPI
• SD Soybean Research and Promotion council.

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We also know that multiple factors interact to
influence reflectance

• Reflectance
• f(water, nutrients, light,
• energy, diseases, insects,
• other)

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Bare soil, 2001
August 24, 2001
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Objectives

• Determine the influence of water and N stress on
  yields and reflectance.

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Field experiment

• N and water experiment was conducted between 2002
  and 2004.
• Remote sensing was measured with a crop scan.
• Carbon and N budgets were determined

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Need to separate N and water stress from each
other

• 13C natural abundance approach was used to
  quantify N and water stress in the plants

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N and water response
Natural irrigation
Natural
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N budget
Soil yield zone Yield Mg/ha N min. Kg/ha WUE Kg/ha cm N from soil (kg N/ha)
Low 8500 72.0 218 80
High 9600 86.0 190 92
P-value 0.004 0.062 0.006 0.027
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N effects
N rate Yield (Mg/ha) WUE kg/ha cm N from soil
0 7510 170 80
56 9040 204 99
112 9890 223 96
168 9800 219 70
P value 0.001 0.001 0.001
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Sampling        
date Parameter Yield YLNS YLWS
12 July NDVI 0.24 -0.41 0.20
 V8-V9 GNDVI 0.67 -0.73 0.02
  Green -0.22 0.24 -0.02
  Red -0.14 0.23 -0.11
  NIR 0.19 -0.48 0.34
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Sampling        
date Parameter Yield YLNS YLWS
Aug. 1-4 NDVI 0.65 -0.22 -0.61
 R1 GNDVI 0.63 -0.65 -0.04
  Green -0.55 0.49 -0.14
  Red -0.48 0.05 0.58
  NIR 0.16 0.27 0.12
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Summary

• Stuff changes
• Early on reflectance sensitive to N but not water
• At R1 (silking) water and N both impacted
  reflectance
• Green N
• Red water

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Models
       
Sampling date Model RMSE N needed ModelYLNS
 V8-V9
12-14 July N stress 16.2 26.4 29000
  Yield model 21.6 30.2 32500
  Yield water stress 21.7 23.6 46400
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Summary

• Water and N stress both impact reflectance.
• N stress early, water stress later
• 13C discrimination can be used separate the
  factors.

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Summary

• Remote sensing models can be used to develop
  corrective treatments.
• The models can be developed using a variety of
  approaches.

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Summary

• The model based on N stress had lowest lost
  opportunity and RMSE.
• Attributed to the water and N cycles being
  interrelated and that the low and high water
  regimes had similar optimum N rates.
• Water increased N mineralization and N increased
  water use efficiency. A sandy soil may have
  different results.