Submitted to: Greenley Research Center Field Day
Publication Type: Abstract Only
Publication Acceptance Date: 8/3/2006
Publication Date: 8/3/2006
Citation: Noellsch, A., Motavalli, P., Nelson, K., Kitchen, N.R., Anderson, S., Scharf, P., Tracey, P. 2006. Variable source n fertilizer applications to optimize crop n use efficiency [abstract]. Greenley Research Field Day, August 3rd, 2006, Novelty, Missouri. p. 70.
Technical Abstract: Use of nitrogen (N) fertilizer in corn has long been essential for improving yields and increasing economic returns. The efficient utilization of N fertilizer is becoming increasingly more important because of rising fertilizer costs and the possible negative impact of environmental N loss. The loss of applied N fertilizer may vary across a field due to several factors including differences in soil physical properties that affect soil water. In addition, enhanced efficiency N fertilizers, such as polymer-coated urea (PCU), a slow-release form of N fertilizer, may improve N utilization by delaying N release under conditions which may promote N loss, or by providing N later in the growing season when plant N requirements are higher. The objectives of this study included: 1)To determine methods to delineate and map areas in fields which are more vulnerable to N loss due to wet conditions; 2) To examine the use of a variable source strategy to optimize crop N fertilizer use efficiency; 3) To calculate the cost-effectiveness of using this variable source strategy compared to uniform applications of conventional or other N fertilizer sources. A two-year field trial was initiated in 2005 at the MU Greenley Experiment Station. The site was mapped for elevation and apparent electrical conductivity (ECa) using an electromagnetic-type ECa sensor (Fig. 1). Nitrogen fertilizer treatments included a control and 4 N source treatments at 150 lb N/acre: 1) urea; 2) polymer-coated urea (PCU) (ESN, Agrium, Inc.); 3) a 50% urea/50% polymer-coated urea mixture; and 4) anhydrous ammonia. N fertilizers were injected (#4) or broadcast-applied and incorporated (#1,2, and 3) in 10 ft by 1500 ft strips across three landscape positions representing shallow, deep and low-lying areas. Rainfall during the 2005 cropping year was relatively low during the growing season with a long period of drought after the middle of June. This lack of rainfall may have reduced possible crop N response. Both polymer-coated urea and anhydrous ammonia had higher grain yields compared to urea in the low-lying area. However, there were no differences among these fertilizer sources at the other landscape positions, which suggest that response to N fertilizer source may vary across fields depending on landscape position. This study is being continued in the 2006 growing season.