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Generalized Algorithm for Variable Rate Nitrogen Application on Cereal Grains. John B. Solie, Regents Professor Biosystems and Agri. Engineering Dept. William R. Raun, Regents Professor, Plant and Soil Sciences Department - PowerPoint PPT Presentation
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Generalized Algorithm for Variable Rate Nitrogen Application on Cereal Grains
John B. Solie, Regents Professor Biosystems and Agri. Engineering Dept.William R. Raun, Regents Professor, Plant and Soil Sciences Department
Dean Monroe, PhD, Formerly Biosystems and Agri. Engineering Department
Normalized Difference Vegetative Index - NDVI• Calculated from the red and
near-infrared bands• Equivalent to a plant
physical examination• Correlated with:
– Plant biomass– Crop yield– Plant nitrogen– Plant chlorophyll– Water stress– Plant diseases– Insect damage
dNIR
dNIRNDVIRe
Re
OSU Original N Rate Algorithm
Bill’s Postulates1. Crop yield potential can be
predicted from NDVI2. A maximum potential yield
exists that is a function of the weather and soil type
3. A fertilizer response index exists that defines the response to additional fertilizer and varies from year to year and site to site.
4. Response to N fertilizer is independent of potential yield.
5. YPN = f(YP0, RI)
1. Measure
2. Predict YP0
3. Predict YPN
4. 1
2
3
4
0YPRIYPN
GDNDVIB
AeYP
NUENYPYPNNRate )%0(
NDVI
NDVINDVI Fp
NRRI
Agronomic Justification for Sigmoid Yield Model
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10
0.2
0.4
0.6
0.8
1
NDVI Vegetative Index
Perc
ent M
ax. P
oten
tial Y
ld.
Bare SoilNo Response
High Response to Change in Biomass & NDVI
Max. YieldPotentialNo Response
Sigmoid Yield Model with Transitions
0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
NDVI Vegetative Index
Perc
ent
Max
. Pot
entia
l Yld
.
Transition to Max. Yld.
Bare Soil
Transition from Bare Soil
Maximum YieldYield Proportional to
Biomass
How Do We Locate the “Curve?
Locate by 1) NDVINRICH and Max. Potential Yield 2) NDVIBareSoil and Zero Yield
0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
NDVI Vegetative Index
Perc
ent
Max
. Pot
entia
l Yld
.
Transition to Max. Yld.
Bare Soil Transition from Bare Soil
Maximum YieldYield Proportional to
Biomass
NRich NDVI
Sigmoid Model Shift from Change in Growth Stage (Biomass)
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10
0.2
0.4
0.6
0.8
1
Mid SeasonEarly SeasonLate Season
NDVI Vegetative Index
Perc
ent
Max
. Pot
entia
l Yld
.
Maximum Potential YieldNRich NDVI
Unit Sigmoid Model
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10
0.2
0.4
0.6
0.8
1
1.2
FpNDVI
Yiel
d
Maximum Potential Yield
Bare Soil Yield
Inflection Point½ Max Yield
+
KFpNDVIMAX
e
YPYP inf
1
Radius of Curvature
Potential Yield Calculations
KFpNDVIRINDVI
e
YPYPN infmax
1
Variables & ParametersYPmaxNDVINRichNDVIFPRINDVI = NDVINRich/NDVIFPInf – Parameter Function of NDVINRich“K” – Parameter Function of NDVINRich
NRich Strip & Potential Yield
NDVI NRICH, NDVIFP NDVIBS: Sense NDVI from NRich strip and adjacent farmer practice strip in a portion of the field exhibiting the highest response to pre-plant fertilizer. Also collect NDVI measurement from bare soil. Calculate RINDVI
POTENTIAL YIELD: Field history, yield trend, farmer’s and agronomist’s knowledge, experience, and intuition, crop models, soils map, etc.
Inflection Point Location
0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1Inf Pt CornInf Pt WheatCornWheat
NDVI Vegetative Index
Infle
ctio
n Po
int -
Cor
n &
Whe
at
Curvature “K”
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
"K" Corn
"K" Wheat
Corn & Wheat
NRNDVI Vegetative Index
Cur
vatu
re "
K"
- Cor
n &
Whe
at
OSU Algorithm Prediction of Yield Compared with Nonlinear Regression of Individual Data Sets
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10
1
2
3
4
5
6
7
8
Expt 502, 2008TC Curve Fit
NDVI Vegetative Index
Whe
at G
rain
Yld
, Mg/
Ha
TableCurve r2 = 0.734ModelPred r2 = 0.734
Fig. 4.a
0 0.2 0.4 0.6 0.8 10
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
LCB, 2006TC Curve FitModel Yld Pred
NDVI Vegetative Index
Whe
at G
rain
Yie
ld, M
g/ha
TableCurve r2 = 0.821ModelPred r2 = 0.821
Fig. 4.b
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10
2
4
6
8
10
Efaw AA 2003
NDVI Vegetative Index
Whe
at G
rain
Yld
, Mg/
Ha
TableCurve r2 = 0.582ModelPred r2 = 0.482
Fig. 4.c
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10
0.5
1
1.5
2
2.5Expt 222,2005TC Curve FitModel Yld Pred
NDVI Vegetative Index
Whe
at G
rain
Yie
ld, M
g/ha
TableCurve r2 = 0.012Model Pred r2= 0.000
Fig. 4.d
Fertilizer Application Rate
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10
102030405060708090
100
Nrate
NDVI
N F
ertil
izer
Rat
e kg
/ha
NUENYPYPNNRate %)0(
Field Test Results
Dr. Bill Raun Eminent Professor and Regents ProfessorOklahoma State University
Spread Sheet Macro for Calculating N Rate
