Submitted to: American Society for Photogrammetry and Remote Sensing Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 11/2/2006
Publication Date: N/A
Citation: Interpretive Summary: High priced energy and nitrogen fertilizer, as well as water quality concerns, is causing producers to consider ways to improve nitrogen use efficiency in corn production. Synchronizing nitrogen availability with crop needs is a step in the right direction because it reduces the potential for nitrate leaching as the result of excessive precipitation. Monitoring the crop for signs of nitrogen stress can be used a trigger for the application of supplemental fertilizer. This study compared information obtain from aircraft imagery, hand-held chlorophyll meters, and sprayer mounted active crop canopy sensors. Results from center-pivot irrigated corn showed good agreement between vegetation indices extracted from aircraft imagery and ground-based data such as SPAD chlorophyll meter readings, active sensor indices, and grain yield. Advances in active sensor technologies make it possible to monitor the crop any time of the day and make simultaneous fertilizer applications as needed. These technologies are able to detect variability in leaf chlorophyll status and plant vigor (probable nitrogen stress) during the growing season, but it is difficult to determine how much fertilizer is required to maintain productivity.
Technical Abstract: Escalating prices of energy and related products like nitrogen (N) fertilizer and pumping costs for irrigation water have done much to increase the appreciation for spatial variability in fields. Because of timeliness and spatial resolution issues, row-crop producers in the U.S. are finding aircraft-based imagery the preferred product for making decisions about nutrient and water stress. Considerable interest has arisen in using ground-based active sensors for mapping soil color at the time of planting and monitoring relative biomass and canopy color during the growing season to assess the need for addition nitrogen fertilizer. Using crop vigor as a biological indicator has many attributes in that real-time decisions can be made when sensors are mounted on high-clearance sprayers. Studies on center-pivot irrigated corn showed good agreement between vegetation indices extracted from aircraft imagery and ground-based data such as SPAD chlorophyll meter readings, active sensor indices, and grain yield. Advances in active sensor technologies make it possible to begin to differentiate between certain types of plant stresses and better integrate the spatial attributes of soils into management decisions.