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American Society of Agronomy
5585 Guilford Road • Madison, WI 53711-5801 • 608-273-8080 • Fax 608-273-2021
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Contact: Hanna Jeske, Associate Director of Marketing and Brand Strategy, 608-268-3972, hjeske@sciencesocieties.org

Precise N Application Yields Optimal Profit

Corn farmers are interested in better methods to help them precisely apply the rate of N fertilizer that will give them optimal profit.

MADISON, WI, February 1, 2010 -- 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. 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.

Agronomy Journal is the flagship journal of the American Society of Agronomy. Articles convey original research in agriculture, natural resources, soil science, crop science, agroclimatology, agronomic modeling, production agriculture, and instrumentation.

The American Society of Agronomy is an international scientific and professional society with its headquarters in Madison, WI. Our members are researchers and trained, certified professionals in the areas of growing our world’s food supply, while protecting our environment. We work at universities, government research facilities and private businesses across the United States and the world.