1. Relationships between SPADs, Aerial Images, and Yield
Gaylia Ostermeier1, Larry Hendrickson1, John Sawyer2
1 John Deere Ag Management Solutions
2 Iowa State University
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2. Trial Design
8 fields with 12 or 16-row treatment strips typically applied the length of field
Treatments were
0, 60, 120, and 240 lb N per acre for CS rotation
0, 90, 180, and 270 lb N per acre for CC rotation
SPAD readings were taken at 89 to 126 locations in each field between V10 and V14
Aerial image typically taken within 3 days of SPAD readings
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4. Data Analysis
Extracted yield, GNDVI, and Relative Vigor (RV) using square regions of interest at each SPAD location
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5. Data Analysis Related yield to SPAD, GNDVI, RV
Definition of 100% for Relative Levels
SPAD—Average of highest N rate for sensor and yields
GNDVI—Average of highest N rate for sensor and yields
RV— Average GNDVI value for “best” representative area and average yield for those pixels
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6. Target Value Definitions
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7. R2 = 0.58
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8. R2 = 0.79
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9. R2 = 0.79
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10. Relationship between Yield and Relative Values
Field
SPAD
GNDVI and RV
Washington
0.58
0.79
Benton
0.42
0.18
Jasper
0.60
0.72
Mahaska
0.01
0.46
Monona-1
0.34
0.48
Monona-2
0.32
0.54
Shelby-1
0.62
Shelby-2
0.07
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13. Conclusions Field SPAD RV Overall 0.35 0.56
Generally, images were equivalent or superior to SPAD readings on both an individual field basis or as a whole
RV can be obtained without reference strips and SPAD readings
29 November 2018