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Title: Alfalfa N credits to second-year corn larger than expected

item Russelle, Michael
item YOST, MATT - University Of Minnesota
item MORRIS, THOMAS - University Of Connecticut
item COULTER, JEFFREY - University Of Minnesota

Submitted to: Forage Focus
Publication Type: Trade Journal
Publication Acceptance Date: 10/14/2013
Publication Date: 12/1/2013
Citation: Russelle, M.P., Yost, M.A., Morris, T.F., Coulter, J.A. 2013. Alfalfa N credits to second-year corn larger than expected. Forage Focus. December issue. p. 4-5.

Interpretive Summary:

Technical Abstract: Alfalfa can provide substantial amounts of nitrogen (N) to the first crop that follows it. Recent field research on first-year corn confirms that it is highly likely that grain yields will not improve with added fertilizer N, except on very sandy and very clayey soils. It is less clear how much fertilizer N is needed for second-year corn after alfalfa termination. In about one-half of the cases in field trials conducted in Iowa and Minnesota, the second crop of corn showed no grain yield response to fertilizer N. In the other cases, maximum yields were obtained with N rates ranging from about 40 to 165 lb N/acre. Literature reports substantiated these findings. We also found direct evidence that, about half of the time, neither first- or second-year corn required additional N to achieve economically optimum yields. Remarkably, growing alfalfa in the rotation reduced the fertilizer bill by about $165 per acre for the two corn crops. The next step in this research will be to create ways to predict which fields of second-year corn need N and how much should be applied.