Title: Using Remote Sensing to Characterize Yield Loss due to Water and N stress in Corn.
1Using 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
2N and water stress
- NASA
- North Central Soybean Board
- SD Corn Utilization Council
- USDA-CSREES
- PPI
- SD Soybean Research and Promotion council.
3We also know that multiple factors interact to
influence reflectance
- Reflectance
- f(water, nutrients, light,
- energy, diseases, insects,
- other)
4Bare soil, 2001
August 24, 2001
5Objectives
- Determine the influence of water and N stress on
yields and reflectance.
6Field 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
7Need to separate N and water stress from each
other
- 13C natural abundance approach was used to
quantify N and water stress in the plants
8N and water response
Natural irrigation
Natural
9N 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
10N 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
11Sampling    Â
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
12Sampling    Â
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
13Summary
- Stuff changes
- Early on reflectance sensitive to N but not water
- At R1 (silking) water and N both impacted
reflectance - Green N
- Red water
14Models
   Â
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
15Summary
- Water and N stress both impact reflectance.
- N stress early, water stress later
- 13C discrimination can be used separate the
factors.
16Summary
- Remote sensing models can be used to develop
corrective treatments. - The models can be developed using a variety of
approaches.
17Summary
- 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.