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ARS Home » Midwest Area » St. Paul, Minnesota » Plant Science Research » Research » Publications at this Location » Publication #306055

Title: Challenges and opportunities for improved N management in corn following alfalfa

Author
item YOST, MATT - University Of Minnesota
item Russelle, Michael
item COULTER, JEFFREY - University Of Minnesota
item DAVENPORT, MAE - University Of Minnesota

Submitted to: Trade Journal Publication
Publication Type: Trade Journal
Publication Acceptance Date: 6/4/2014
Publication Date: 6/16/2014
Citation: Yost, M.A., Russelle, M.P., Coulter, J.A., Davenport, M.A. 2014. Challenges and opportunities for improved N management in corn following alfalfa. Clippings. June 16, 2014.

Interpretive Summary:

Technical Abstract: With some exceptions, the alfalfa nitrogen (N) credit usually eliminates the need for manure N and/or fertilizer N to economically optimize yield of the first corn crop following alfalfa. Alfalfa also can provide nearly one-half or more of the N requirement for the second corn crop following alfalfa. These results have been confirmed with modern corn hybrids in over 40 on-farm research trials in Minnesota during the past five years. When alfalfa or manure N credits are not used for first- and second-year corn following alfalfa, total N rates can become excessive quickly. A survey of Minnesota growers was conducted in 2012 to better understand challenges to and opportunities for improved N management in corn following alfalfa. Results from 421 growers in Minnesota indicate low adoption of alfalfa and manure N credits for first-year corn. Adoption rates were slightly higher when no manure was applied to first-year corn (40%) than when it was applied (30%), but the majority of growers (67%) applied manure. By not fully accounting for alfalfa N credits for first-year corn, most growers (62%) without manure who exceeded Extension guidelines applied 100 to 150 lb N/acre above guidelines. When the combined N credits for manure and alfalfa were not fully accounted for, one-third of growers exceeded guidelines by more than 150 lb N/acre. There were 273 of 421 growers who planted two years of corn following alfalfa. Again, adoption was slightly higher without manure (33%) than when it was applied (25%), but most growers applied manure (79%). When manure was applied to one or both corn crops following alfalfa, almost one-half of the growers who exceeded guideline rates (75% of growers) did so by more than 150 lb N/acre. A vital need exists to improve both alfalfa and manure N credit adoption because excess N application often can reduce farm profit, waste resources, and impair water quality. The efforts to improve N credit adoption will need to address the challenges of N management in corn following alfalfa, some of which are outlined in this article. We offer a few suggestions for improvement, which are based on Minnesota Extension guidelines.