ARS | Publication request: Sensing Corn for Nitrogen Fertilizer Need Makes Sense

Submitted to: CSA News
Publication Type: Popular Publication
Publication Acceptance Date: November 5, 2010
Publication Date: November 6, 2010
Citation: Kitchen, N.R. 2010. Sensing Corn for Nitrogen Fertilizer Need Makes Sense. CSA News. 55(2):10.

Technical Abstract: With increasing costs for crop inputs, corn farmers are interested in better methods to help them precisely apply the rate of nitrogen (N) fertilizer that will give them optimal profit. Additionally, environmental concerns continue because a large amount of N from agricultural fields moves into streams, rivers, and oceans. Since more N fertilizer is applied to corn than any other crop, interest is high for exploring new technologies for improved corn N management. In recent years, light reflectance sensors have been proposed and tested as a technology on which to base side-dress variable-rate N applications in corn. A critical element captured with this sensing strategy is that it accounts for differences within fields associated with soil and landscape factors. The purpose of this research was to assess the utility of these sensors for on-the-go variable-rate N fertilization in corn that increase profits and decrease N losses from fields. We found the amount of N the corn crop needed varied within most fields by over 100 lbs per acre, reinforcing the need for precision technologies that enable variable-rate N fertilization. Findings over three diverse Missouri soil types demonstrate sensor-based N fertilizer applications could generate an increase in returns ranging from $10 to $20 per acre. As fertilizer cost increases relative to the price of corn grain, the value of using canopy sensors for N management improves more. Differences were also observed when comparing soil types. River bottom soils appeared to be especially well-suited for this technology. The amount of N saved when using the sensors ranged from 10 to 50 lbs /acre, depending on soil type and fertilizer and grain prices. The results of this study are being used to develop procedures and decision rules for how much N to apply in corn using canopy sensors. Farmers will benefit because they can reduce excess N applications, which with increasing N fertilizer cost, should save them money. If fertilizer can be better matched with crop need, N loss to lakes and streams will be reduced and the environment will be improved.