Using the Presidedress Soil Nitrate Test and Organic Nitrogen Crediting to Improve Corn Nitrogen Recommendations
- Todd W. Andraski * and
- Larry G. Bundy
The PSNT and N crediting for organic N inputs can improve the accuracy of corn (Zea mays L.) N recommendations, but are often not used due to producer concerns about their reliability. This study compared the use of these techniques for identifying optimum N rates and quantifying economic returns in 101 N response field experiments with corn conducted during 1989–1999. The accuracy of PSNT recommendations was highest for sites with average or above average May–June air temperatures and high soil yield potential. The frequency of excess N recommendations from the PSNT increased from 16 to 59% when May–June temperatures were >0.56°C below average likely due to slower organic N mineralization. Use of N recommendations based on the PSNT or book value N credits (BVNC) lowered N rates by 90 to 102 kg ha−1 in systems with recent manure or legume N inputs and increased average economic returns for all cropping systems by $19 ha−1 compared with unadjusted N recommendations (i.e., economic gain). Economic gains using PSNT- or BVNC-based recommendations were generally highest in the first year following organic N inputs with an average gain of $34 ha−1 for both methods. Conversely, economic gains were higher using the PSNT ($40 ha−1) than the BVNC ($2 ha−1) 1 to 3 yr after the organic N additions on high yield potential soils where May–June air temperatures were average or above. Results from this work confirm that adjusting N application rates for corn using the PSNT or BVNC is more profitable than not making these adjustments.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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