Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 11/14/2006
Publication Date: 11/14/2006
Citation: Hong, N., Scharf, P.C., Davis, J.G., Kitchen, N.R., Sudduth, K.A. 2006. Economically optimal nitrogen rate reduces soil residual nitrate. ASA-CSSA-SSSA Annual Meeting Abstracts.
Technical Abstract: Practices that minimize post-harvest residual soil NO3-N (RSN) can reduce N loss to the environment. Our objectives were to determine if the RSN after corn (Zea mays L.) harvest can be reduced if N fertilizer is applied at the economically optimal N rate (EONR) as compared to current producers' practices in the midwestern U.S., and to compare RSN levels if no N fertilizer is applied to RSN levels if N fertilizer is applied at a rate below, at, or above the EONR. Six experiments were conducted in producers' fields over 2 yrs. At four transects in each field, six treatment N rates from 0 to 280 kg/ha were applied, the EONR was determined, and the RSN was sampled to a 0.9-m depth from five treatment plots. The EONR at sampling sites varied from 49 to 228 kg/ha depending on site-year. Estimated average RSN at the EONR was 27 kg/ha in the 0.9-m profile. Applying fertilizer N at the EONR reduced the RSN by at least 11 kg/ha compared to the producer's rate. The RSN increased with increasing difference from EONR (total N applied - EONR). When the difference from EONR < 0, average RSN was 21 kg/ha and was not different than if total N applied was zero or equal to the EONR. When 0 < the difference from EONR < 50 kg/ha, average RSN increased to 39 kg/ha, but was not greater than when the difference from EONR = 0. When 50 < the difference from EONR < 100, average RSN increased to 49 kg/ha, and was greater than when the difference from EONR = 0. When the difference from EONR > 100 kg ha-1, average RSN significantly increased to 91 kg/ha. Our results suggest that applying the EONR will produce environmental benefits in an economically sound matter.