Monday, November 5, 2007
51-6
Evaluation of Canopy Reflectance for Optimizing Nitrogen in Corn.
Adam Pfeffer1, Bill Deen1, and Greg Stewart2. (1) Plant Agriculture, Univrsity of Guelph, 5 Stone Rd., Guelph, ON N1G 2W1, Canada, (2) Ontario Ministry of Agriculture and Food, 5 Stone Rd., Guelph, ON N1G 2W1, Canada
Whether variable rate N application technology, based on the spectral reflectance of the crop canopy, can improve N use efficiency and corn performance on a farm scale was evaluated in 2006 and 2007 in Ontario A GreenSeeker RT200 Variable Rate Application and Mapping System (Ntech Industries, Inc) was used to measure NDVI on three starter nitrogen treatments: 1) four rows with 0 kg N ha-1 relative to four rows in a fully fertilized reference strip, 2) four rows with 30 kg N ha-1 applied as a side band relative to four rows in a fully fertilized reference strip, and 3) two rows with 0 kg N ha-1 relative to two immediately adjacent rows with 60kg N ha-1 applied as a sideband. Treatments were replicated three times and were 150m in length. Each treatment was subdivided into 10m plots and average NDVI measurements for each subplot were taken at the 7, 8, 9, 10, and 11 leaf stages of corn. In 2007 an additional measurement was taken at the 13 leaf stage. To determine nitrogen responsiveness of each subplot, 0 and 150 kg N ha-1 plots were placed on either side of each subplot, thus enabling a delta yield measurement. In 2006, for treatment 2 and 3, NDVI values were not correlated with delta yield at any of the NDVI measurement stages. In 2006, for treatment 1, positive correlations between NDVI and delta yield were only observed at the 11 leaf stage. Potential yield losses associated with zero starter nitrogen and delayed side-dress nitrogen may limit usefulness of spectral reflectance technology for variable nitrogen application.