Optimum nitrogen fertilization rates for second-year corn succeeding alfalfa under irrigation

The N contribution of alfalfa (Medicago sativa L) to the succeeding corn (Zea mays L) crop (FYC) is widely recognized. However, there is less information regarding the optimum N fertilization rates (ONR) for a second-year corn (SYC) following alfalfa. Thus, the objective of this study was to evaluate the response of SYC after alfalfa to N fertilization under irrigated semiarid conditions. Three field experiments of SYC following alfalfa were conducted between 2007 and 2009 in Northeast Spain. Treatments included the combination of six N rates applied to FYC (0, 50, 100, 150, 200, and 300 kg N ha(-1)) with four N rates applied to SYC (0, 100, 200, and 300 kg N ha(-1)). In one of the three fields, high SYC yields (16.8 Mg ha(-1)) were obtained in plots that remained unfertilized during two consecutive years after alfalfa. On the other two fields, 81-100% of the maximum corn yields were obtained with application of 200 kg N ha(-1) to SYC. Results suggest that the typical N fertilizer rates applied to SYC after alfalfa in irrigated semiarid areas (300 kg N ha(-1)) could be reduced by at least 100 kg N ha(-1), with small or no economic penalties and important reductions in N losses. (C) 2011 Elsevier B.V. All rights reserved.