News Release

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. These differences result in various levels of N from soil organic matter as well as varied amounts of N loss from fields (e.g., leaching, runoff, or gaseous emissions). 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.

 

Results of this study appear in the January-February 2010 issue of the Agronomy Journal. Newell R. Kitchen and others at the University of Missouri conducted 16 experiments on producer fields over four seasons (2004-2007) in three major soil areas in Missouri.

 

Multiple blocks of N rate response plots traversed the length of each field, with each block consisting of eight treatments (0 to 210 lb/A on 30 lb/A increments) applied at the same time as plant sensing. Additionally, canopy reflectance readings were also obtained at this time from an adjacent non-N-limiting area. At the end of the growing season, yield and optimal N rate were determined for each block of N rate treatments and compared to the sensor information. From these results the most profitable N rate was determined relative to fertilizer costs and corn grain prices.

 

"In this investigation we found the amount of N the corn crop needed varied within most fields by over 100 pounds per acre, reinforcing the need for precision technologies that enable variable-rate N fertilization," noted Kitchen.

 

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 lb/A, 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. In Missouri, USDA-NRCS has adopted the findings of this research and offer producers support through the EQIP program. 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.