Corn N Sensor Calibration.

The objectives of this project are to develop a crop sensor-based calibration for sidedress N application to corn, evaluate the most appropriate corn growth stage for the calibration algorithm, design a reference calibration strip appropriate for commercial field adoption, and evaluate the Greenseeker sensor mounting configurations and usage protocols.  Results from 6 N fertilizer response experiments conducted in 2013 and 2014 on Tidewater, Coastal Plain, and Mountain region sites will be presented. A starter band application of 6 lb N/ac (5 gpa of 11-37-0) was applied to all plots in all experiments. Check plots (0 N) and a range of N fertilizer rates (50, 100, 100, and 250 lb N/ac)  were also applied at planting. Following crop sensing with a Trimble Greenseeker unit (and with a chlorophyll meter) additional N treatments were applied at V-7 or V-12 sidedress. Initial results document greater response to sidedress N at lower initial N application rates, and greater yield responses to N at higher measured spectral response indexes. Relative NDVI values will also be described for measurements collected at multiple plant height scenarios.