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Validating Top-Dressed K Fertilizer Recommendations in an Alfalfa-Corn Rotation

Study author(s): Michael Russelle, USDA Agricultural Research Service
Years of study: 2008
Location(s): Olmstead, Dakota, Wright, Morrison, Dodge, Carver, and Stearns Counties.

Important: for the complete report, including all tables and figures, please download using the link(s) to the right.


We completed two years of on-farm research on alfalfa response to potash application in the last year of forage production. There was no alfalfa yield response to potash. Forage quality in 2008 at 5 farms also showed no response, except for NDF digestibility, but the improvement in NDFD would not affect milk production in total mixed rations. Forage quality analysis from 2009 is being completed. A French student intern helped develop a rapid plant K extraction procedure in summer 2009. Corn grain and silage yield in 2009 did not respond to previous potash treatments or to fertilizer N, confirming that alfalfa provided sufficient N to the first corn crop. Corn yield was increased, however, by addition of fertilizer K in spring. Five remaining sites will be in the corn phase in 2010. We expanded the corn phase of the AFREC-funded research with new funds from the Minnesota Corn Research and Promotion Council. This allowed us to attract a graduate student, who is working directly with the cooperating farmers, and will enhance the outputs of this AFREC project by including K removal in alfalfa, determining the potential ethanol yield from corn grain, cobs, and stover, and measuring residual soil inorganic N after corn harvest.

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