ARS | Publication request: EVALUATION OF VARIABLE RATE NITROGEN APPLICATION STRATEGIES

Submitted to: Annual Missouri Water Quality Conference
Publication Type: Proceedings
Publication Acceptance Date: September 15, 1995
Publication Date: N/A

Technical Abstract: Using University of Missouri recommendations, a "field average" target yield and soil-test organic matter content and cation exchange capacity are used to determine the amount of nitrogen (N) fertilizer to apply for crop production. However, the yield potential and subsequent N needs of the crop differ by as much as 2:1 from point-to-point within fields. The purpose of this research was to use mapped yield and soil information to develop methods for determining where N fertilizer rates should be varied, and to compare these methods with the conventional approach of applying a single N rate to a field. Two methods for determining variable N fertilizer rates for corn were evaluated, a yield map method and a depth to claypan method. Both improved our ability to predict target yield and crop N requirements over using "field average" yield goals. Yields were generally as good with the variable rate treatment as with the single rate treatment, while total N amounts were reduced. Post-harvest soil nitrate levels were sometimes less with the variable rate treatment.