1. 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

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

3. Seven Field Research Sites

5. 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

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

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

9. RESULTS

10. Yield at Economic Optimal N Rate by Site

11. Economic Optimal N Rate by Site

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

14. Reference Strips
Ratio

26. 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.

27. 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.