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Title: Stand age affects fertilizer nitrogen response in first-year corn following alfalfa

Author
item YOST, MATT - University Of Minnesota
item Russelle, Michael
item COULTER, JEFFREY - University Of Minnesota
item SCHMITT, MICHAEL - University Of Minnesota
item SHEAFFER, CRAIG - University Of Minnesota
item RANDALL, GYLES - University Of Minnesota

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/14/2014
Publication Date: 2/25/2015
Publication URL: http://handle.nal.usda.gov/10113/61177
Citation: Yost, M.A., Russelle, M.P., Coulter, J.A., Schmitt, M.A., Sheaffer, C.C., Randall, G.W. 2015. Stand age affects fertilizer nitrogen response in first-year corn following alfalfa. Agronomy Journal. 107:486-494. DOI: 10.2134/agronj14.0493.

Interpretive Summary: Recent research has identified problems with current fertilizer nitrogen recommendations for corn following alfalfa that are based on the population density of alfalfa, the criterion used by most states in the Midwest. The result is that some corn growers may be applying too much nitrogen fertilizer, while others may be applying too little. A recent analysis of published research indicated that corn nitrogen response appears to be affected by alfalfa stand age, soil texture (sandy vs. loamy vs. clayey), weather, and time of alfalfa termination. Collaborative research between an ARS scientist in St. Paul, MN, and colleagues at the University of Minnesota conducted research that, for the first time, directly tested the effect of alfalfa stand age on nitrogen need in the following corn crop on a loamy and on a clayey soil. Their findings indicate that older stands supply more nitrogen than younger stands, and that the effect appears to be greater on loam soils than on clayey soils. The population density of alfalfa did not relate to fertilizer need by the corn. This research confirmed that new approaches to predicting the fertilizer needs of corn grown after alfalfa need to be developed and tested, and this research indicates at least two factors that should be considered in future research.

Technical Abstract: The amount of N that alfalfa (Medicago sativa L.) provides to subsequent first-year corn (Zea mays L.) depends, in part, on the age of alfalfa at termination. Our objective was to determine how alfalfa stand age affects N availability and fertilizer N requirements for first-year corn. Fertilizer N was applied to no-tillage corn following fall-terminated 1-, 2-, and 3-yr-old alfalfa stands with stand densities of 33 to 579 plants/m2 at Lamberton and Waseca, MN for each of three years. At both locations, alfalfa stand age had minor impacts on soil inorganic N content and aboveground corn DM yield, N concentration, and N uptake during first-year corn following alfalfa. On medium-textured soil at Lamberton, first-year corn following 3-yr-old alfalfa stands required no fertilizer N to economically optimize grain yield, but required 64 and 97 kg N/ha following 2- and 1-yr-old stands, respectively. On fine-textured soil at Waseca, first-year corn required 94 kg N/ha following both 2- and 3-yr-old stands and 118 kg N/ha following 1-yr-old stands. Therefore, current alfalfa N credit guidelines from land-grant universities that are based on alfalfa stand density at termination were not accurate for 1- to 3-yr-old alfalfa stands with frequently high final densities. The results also confirm that both alfalfa stand age and soil textural class affect the frequency and level of fertilizer N response in first-year corn. Further research is needed to quantify and predict how older alfalfa stands contribute greater amounts of N to subsequent corn crops on various soils.