Relationships between SPADs, Aerial Images, and Yield Gaylia Ostermeier1, Larry Hendrickson1, John Sawyer2 1 John Deere Ag Management Solutions 2 Iowa State University 29 November 2018

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 29 November 2018

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Data Analysis Extracted yield, GNDVI, and Relative Vigor (RV) using square regions of interest at each SPAD location 29 November 2018

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 29 November 2018

Target Value Definitions 29 November 2018

R2 = 0.58 29 November 2018

R2 = 0.79 29 November 2018

R2 = 0.79 29 November 2018

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 29 November 2018

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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