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Title: On-Farm Validation of Alfalfa N Credits to Corn

Author
item COULTER, JEFF - University Of Minnesota
item Russelle, Michael
item SHEAFFER, CRAIG - University Of Minnesota
item KAISER, DAN - University Of Minnesota

Submitted to: Extension Reports
Publication Type: Trade Journal
Publication Acceptance Date: 1/27/2010
Publication Date: 2/1/2010
Citation: Coulter, J., Russelle, M.P., Sheaffer, C., Kaiser, D. 2010. On-Farm Validation of Alfalfa N Credits to Corn. University of Minnesota Extension Forage Program, Forage Quarterly. 4(1):3.

Interpretive Summary:

Technical Abstract: Rotating alfalfa with corn is useful for reducing soil erosion, enhancing soil tilth and carbon storage, reducing weed seedbanks, disrupting the life cycles of disease and insect pests of corn, and supplying nitrogen (N) to the subsequent corn crop. To adjust N fertilizer rates for corn following alfalfa, growers should subtract the appropriate alfalfa N credits from the N fertilizer rate they would apply to corn following corn. With the high cost of N fertilizers, improved corn genetics, higher yields, and tight economic returns, validation of the University's alfalfa N credit guidelines is important to ensure grower success. In the spring of 2008, with funding from the Minnesota Agriculture Fertilizer Research and Education Committee, on-farm experiments were established in third- or fourth-year alfalfa fields at five locations ranging from southeast to central Minnesota. After corn planting, five N fertilizer rates (0, 20, 40, 80, and 160 lb N/acre) were broadcast as ammonium nitrate within each of the larger plots that received the different rates of K fertilizer during the previous year of alfalfa. At all locations, corn silage and grain yields were high and not affected by the rate of N fertilizer applied to corn. These results demonstrate the ability of reasonable alfalfa stands to supply adequate N to first-year corn over a range of soil and climatic conditions. In 2010, research will be conducted at an additional five locations to improve our confidence in these results.