|YOST, MATT - University Of Minnesota|
|COULTER, JEFFREY - University Of Minnesota|
Submitted to: American Society of Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 6/26/2013
Publication Date: 11/3/2013
Citation: Yost, M.A., Russelle, M.P., Coulter, J.A. 2013. Simple, effective predictors of nitrogen need for corn following alfalfa [abstract]. ASA-CSSA-SSSA 2013 International Annual Meeting. November 3-6, 2013, Tampa, Florida. Abstract No. 278-8. Available: https://dl.sciencesocieties.org/publications/meetings/2013am/11705/81323.
Technical Abstract: The most extreme cases of excessive N fertilization in corn (Zea mays L.) often occur when following alfalfa (Medicago sativa L.). Although fertilizer N requirements of first-year corn following alfalfa have been extensively studied for the last 50 years, current state recommendations often are incorrect and many growers do not follow them. We conducted a meta-analysis of 272 site-years from the literature to determine: 1) which site-years of first-year corn responded to fertilizer N; and 2) the economically optimum N rate (EONR) for responsive sites. Combinations of simple predictors (soil texture, alfalfa termination timing, alfalfa stand age, and weather conditions) were adequate for both objectives. Responsive and non-responsive sites were identified correctly before corn planting in over 90% of the cases on fine-textured soils and on medium-textured soils with spring alfalfa termination, and in 77% of the cases on medium-textured soils with fall alfalfa termination. Only one of 11 trials did not respond to fertilizer N on coarse-textured soils, preventing development of a logistic regression model. However, 89% of the variation in actual EONR on coarse-textured soils could be accounted for by alfalfa termination time and weather conditions prior to planting. On fine-textured soils and medium-textured soils with spring termination, 95 to 97% of the variation in EONR could be accounted for by alfalfa stand age and weather conditions prior to sidedressing time. Prediction of the EONR on medium-textured soils with fall termination was poor, and actual EONR varied widely (47-224 kg N/ha). This novel approach to field-specific fertilizer N recommendations for first-year corn following alfalfa should greatly improve fertilizer use efficiency, enhance acceptance of the recommendations by growers, and reduce N loss; this approach also may prove effective for other rotations.