Submitted to: Agronomy Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/20/2009
Publication Date: 5/8/2009
Citation: Noellsch, A.J., Motavalli, P.P., Nelson, K.A., Kitchen, N.R. 2009. Corn Nitrogen Response Across a Claypan Landscape Using Polymer-Coated Urea and Anhydrous Ammonia. Agronomy Journal. 101:607-614. Interpretive Summary: Grain producers traditionally work to optimize crop nutrient use efficiency by carefully selecting the best performing fertilizer source, rate, timing, and placement methods available. Usually the greatest efficiency is obtained when the right rate is applied at the right time, and rightly placed for maximum root uptake. However for any of these management considerations, what is best may vary within a field. This is especially the case with N fertilizer, since potential for leaching or gaseous N emissions can be extremely variable within the same field. Therefore, the best set of management practices for one part of a field may not be optimal for another area of the same field. This study was conducted to investigate the potential for increased corn yield and nutrient use efficiency by using a slow-release, polymer-coated, urea-N fertilizer in field areas prone to N loss because of excess moisture. The investigation was conducted on a poorly-drained claypan soils, found on over 10 million acres in the US Midwest. We found that yield and N fertilizer use efficiency were increased about 15 to 25% when comparing the slow release fertilizer to conventional urea fertilizer, but only at the low-lying landscape position where the soils stayed wetter during the growing season because of runoff from upslope. Based on these results, we concluded significant N fertilizer is lost on these soils when fertilizer N changes to gaseous forms and escapes the soil into the atmosphere. Performance of the slow-release formulation was comparable to another readily-available N fertilizer called anhydrous ammonia fertilizer. These findings demonstrate that applying slow-release fertilizer may be especially beneficial when targeted to field areas that remain wet for extended periods during the spring and early summer. For the farmer, higher nutrient use efficiency with this practice translates into better economic returns. Concurrently, adoption of this practice can reduce fertilizer N losses to rivers and into the atmosphere as a greenhouse gas.
Technical Abstract: Improvement of N fertilizer recovery efficiency (NRE) is necessary to reduce the detrimental effects of excess N entering the environment and to increase economic returns from applying N fertilizer to crops. A two-year field trial was established in 2005 in Northeast Missouri to determine the effects of conventional and slow-release N fertilizer sources and landscape position on crop growth and NRE in corn (Zea mays L.) for a claypan soil. The study was a split-plot design with four replications, which traversed three landscape positions (summit, sideslope, and toe-slope). Nitrogen fertilizer treatments consisted of a non-fertilized control and pre-plant applied and incorporated N treatments of urea, polymer-coated urea (PCU), 50% PCU/50% urea mix, and anhydrous ammonia, applied at 168 kg N/ha. In-season gravimetric soil water content data from several dates in 2005 and 2006 indicated that the toe-slope landscape position was often wetter than the summit and/or sideslope positions. Anhydrous ammonia and PCU treatments increased grain yield 1470 to 1810 kg/ha over urea in the toe-slope landscape position in 2005 and 2006. Plant N uptake in 2005 for PCU and anhydrous ammonia treatments were 36 and 47 kg/ha greater than the urea treatment, respectively, at this landscape position. Observed NRE in the anhydrous ammonia treatments in 2005 was 28% higher than urea in the toe-slope area. In addition, PCU, PCU/Urea, and anhydrous ammonia treatments in the toe-slope position had between 17 to 35% higher NRE than at the summit or sideslope positions. These results suggest show promise for a variable N fertilizer source management strategy using conventional and slow release N fertilizers applied to different areas of a field based on degree of wetness. Further testing of this strategy is necessary to determine whether it would be effective under a variety of environmental conditions and cultural practices.