Corn Nitrogen Management Using Reflectance Sensors: Missouri 2004 Field-Scale Results Newell R. Kitchen, Kenneth A. Sudduth USDA-ARS, Columbia, MO Peter Scharf, Harlan Palm, and Kent Shannon Univ. of MO, Columbia, MO

Active Light Sensors Two types of active-light sensors “green” GreenSeeker by NTech Crop Circle by Holland Scientific

Seven Field Research Sites

Individual plots 15 x 50 ft RCB with 8 treatments Application rates: 0, 30, 60, 90, 120 150, 180, and 210 lb N/acre Sites had between 3 and 10 blocks of response plots Economic Optimal N rate (EONR) determined using a quadratic-plateau fit for each block

Sensor and N applications at V8-V10 Sensors were adjusted to be ~ 20 inches above the N-rich reference strip corn

Nitrogen Recommendation for Knee- to Waist-High Corn Missouri 2004-05 Algorithm - Ceiling for Reference set to 0.25

RESULTS

Yield at Economic Optimal N Rate by Site

Economic Optimal N Rate by Site

Between 200-300 readings/plot Between 1600-2400 readings/block N Reference from interpolated maps of strip treatments adjacent to response plots

Reference Strips Ratio

EONR prediction is not easily accomplished, and is more of a challenge in rainfed environments. If one could reliably predict yield, this factor alone does not do a good job of predicting EONR. In 2004 and averaged over all sites, we achieved ~$5/acre more profit when using the sensors when compared to the farmer’s single blanket rate. Data needs to be collected to test current and yet-to-be developed algorithms.

Research supported in part by the USDA- NRI and IFAFS Grant Programs Research supported in part by the USDA- NRI and IFAFS Grant Programs. Assistance also given by OSU, NTech, and Holland Scientific Instruments.