Effect of Crop Canopy Sensor Density on Predictability of Nitrogen Stress in Corn.

Active canopy sensors are being studied as a practical tool to assess in-season crop N status and control on-the-go site-specific N application. This study was conducted to evaluate the optimum sensor spacing for N application in corn. Research was conducted during the 2007 growing season on four irrigated cornfields in central Nebraska. Data was collected once from 24 consecutive rows within each field at growth stages ranging from V9-V17. A base map assumed to be the most accurate measurement of chlorophyll index (CI) for each study area was created using square pixels equal to the row spacing (0.91 m). A variety of split- and whole-boom sensor spacing scenarios were compared to the base map using mean squared error calculations. Anisotropic semivariograms were used to evaluate the spatial structure of CI. Averaging sensor readings across the entire 24 row boom produced the most accurate prediction of CI for three of the four fields.  Results from the four fields indicated there was no substantial benefit to using more than 2-3 sensors to estimate an average CI for the 24 row study area. Sensor readings will be collected from additional fields during the 2008 growing season. Data analysis results for the two years will be presented at the international annual meetings.