Submitted to: Geospatial Information in Agriculture and Forestry International Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/12/2000
Publication Date: N/A
Technical Abstract: The optimal nitrogen (N) rate to meet crop needs varies widely from year to year as well as spatially within farm fields. The objective of this work was to determine site-specific N rates that were adequate to meet crop needs and would decrease N loss to the environment with no reduction in grain yield. Based on previous work, it was hypothesized that soil electrical conductivity (EC) would be correlated to N need. Uniform N rates were applied in strips across the range of EC levels present in the study fields. Within-season crop N status was monitored using chlorophyll meter readings as indicators of N sufficiency, with sampling transects selected based on EC level. Grain yields were measured using a combine with yield monitor. Optimum N rates were determined for various landscape positions and EC levels by using side-by-side transect data to generate yield response curves. Within fields, there was a wide variation in the optimum N fertilization rate. Chlorophyll concentration and optimum N rat as determined from yield data were not always consistent, probably because of lower N use efficiency at higher N fertilization rates.