Sensor Based Nitrogen Management for Irrigated Corn.

The efficient use of nitrogen (N) fertilizer in irrigated corn production (Zea mays L.) is important for maximizing economic returns for producers, and minimizing nitrate additions to groundwater.  A multi-site/multi-year experiment was conducted on sites differing in leaching potential and in areas with substantially different rainfall and ET patterns. The objectives of this research were to quantify the impact of various N management systems on nitrogen use efficiency and grain yield, and to determine the impact of the tested N management strategies on potential nitrate leaching.  This study included pre-plant N applications ranging from 134-224 kg N ha^-1, split applications of N at the same rates with 50% applied pre-plant and the remainder as a sidedress application at approximately the V-8 growth stage, and split application systems based on sensor technologies which included utilization of the SPAD meter, GreenSeeker red and the Crop Circle amber sensors.  Grain yields were optimized at all sites with considerably less N than is normally recommended.  Only limited response to split applications of N were found at most sites and good predictions of actual N needs was obtained using the active sensors.