IRRIGATED CORN AND SOYBEAN RESPONSE TO NITROGeN UNDER NO-TILL IN NORTHERN COLORADO

Authors: Halvorson, Ardell; Reule, Curtis

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/11/2006
Publication Date: 9/5/2006
Citation: Halvorson, A.D., Reule, C.A. 2006. Irrigated corn and soybean response to nitrogen under no-till in northern colorado. Agronomy Journal. 98:1367-1374.

Interpretive Summary: A 5-yr field study was conducted to determine the viability of an irrigated, no-till (NT) corn-soybean production system in northern Colorado and the N fertilizer needs to optimize crop yields within the rotation. Converting from an intensive conventional tillage production system to a NT system can potentially reduce soil erosion, fossil fuel consumption, and greenhouse gas emissions. Six N rates, established in 2000, were used to determine the N needs to maximize corn and soybean yields in the rotation. Corn grain yields increased with increasing N rates each year, but soybean did not respond to N fertilization, with an average yield of 2787 kg/ha. Corn grain yields were near maximum with an available N (soil + fertilizer N) level of 271 kg N/ha and a total N requirement of 21 kg N/Mg grain produced. Nitrogen fertilizer use efficiency by corn averaged 41%. Corn residue production increased with increasing N rate, but soybean residue production did not vary with N rate. Excellent corn yields were obtained in this corn-soybean rotation for northern Colorado, but soybean yields were only marginally acceptable. Short soybean plant height (30-40 cm) and shattering made combine harvest difficult resulting in significant grain loss. Current N fertilizer recommendations used for CT corn based on yield goal would appear to be useable for NT corn grown in a corn-soybean rotation in northern Colorado.

Technical Abstract: No-till (NT) irrigated production systems can potentially reduce soil erosion, fossil fuel consumption, and greenhouse gas emissions compared with conventional till (CT) systems. Including a legume in the rotation may also reduce N fertilizer requirements. Nitrogen fertilization (6 N rates) effects on irrigated, corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] yields in a corn-soybean rotation were evaluated for 5-yr on a clay loam soil to determine the viability of an irrigated NT system and N needs for optimum crop yield. Corn grain yields were significantly increased by N fertilization each of three years in the rotation, but soybean grain yields (2-yr) did not respond to N fertilization, averaging 2787 kg ha-1. Corn grain yields were near maximum with an available N (soil + fertilizer N) level of 271 kg N ha-1. Nitrogen fertilizer use efficiency (NFUE) by corn tended to decrease, but not always significantly, with increasing N rate, averaging 41% over N rates and years. Total N required to produce one Mg grain at maximum corn yield averaged 21 kg N Mg-1 grain. Corn residue increased with increasing N rate but soybean residue was constant across N rates. Excellent corn yields were obtained in this corn-soybean rotation for northern Colorado, but soybean yields were only marginally acceptable. Short soybean plant height (30-40 cm) and shattering made combine harvest difficult resulting in significant grain loss. Current N fertilizer recommendations used for CT corn based on yield goal would appear to be useable for NT corn grown in a corn-soybean rotation in northern Colorado.