|COULTER, JEFFREY - University Of Minnesota|
|YOST, MATT - University Of Minnesota|
|MORRIS, THOMAS - University Of Connecticut|
Submitted to: American Society of Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 6/26/2013
Publication Date: 11/3/2013
Citation: Coulter, J.A., Yost, M.A., Morris, T., Russelle, M.P. 2013. Field-specific N recommendations for second-year corn after alfalfa [abstract]. ASA, CSSA, & SSSA 2013 International Annual Meeting. Nov. 3-6, 2013, Tampa, FLorida. Abstract No. 135-8. Available: https://dl.sciencesocieties.org/publications/meetings/2013am/12478/81712.
Technical Abstract: When alfalfa (Medicago sativa L.) is terminated, N from soil organic matter and decomposing alfalfa shoots, crowns, and roots becomes available for at least two years of subsequent corn (Zea mays L.) crops. Current state recommendations reflect the fact that fertilizer N requirements of second-year corn following alfalfa have been studied much less than first-year corn. In several states, fertilizer N recommendations are the same for continuous corn and second-year corn following alfalfa, while other states recommend reducing the amount of N applied to second-year corn by 25 to 145 kg N/ha. The variability and inconsistency in N recommendations for second-year corn needs to be addressed. On-farm experiments were conducted at 28 farms in Minnesota and Iowa to determine fertilizer N requirements of second-year corn following alfalfa. Surprisingly, half of the farms required no fertilizer N to increase grain yield. The remaining 14 responsive farms had variable economically optimum N rates ranging from 75 to 269 kg N/ha. These results indicate that the second-year N credit is highly variable and that book value N credits or the average EONR for second-year corn are not accurate. A suite of predictor variables (soil, weather, and first-year corn characteristics) will be used to identify second-year corn fields that do not require fertilizer N to increase grain yield and to predict the EONR on responsive sites. Field-specific N recommendations for second-year corn should greatly improve N management, thereby increasing net returns for growers and reducing environmental impacts of over fertilization.