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Alfalfa/Corn Growers Needed for On-Farm Research in Southern Minnesota

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By Jeff Coulter - Extension Corn Agronomist; and Michael Russelle - USDA Soil Scientist


With the high cost of nitrogen (N) fertilizers, improved corn genetics, and tight economic margins, the University's guidelines for the alfalfa N credit to corn need to be tested and refined. Current University of Minnesota fertilizer guidelines are to reduce fertilizer N on first-year corn after alfalfa by 150 lb/acre when 4 or more alfalfa plants/sq. ft. are present, 100 lb/acre for 2 to 3 plants/sq. ft., and only 40 lb/acre for 1 or fewer plants/sq. ft. The cost savings for corn production are huge for growers that accept these alfalfa N credits and reduce fertilizer input accordingly.


Current University recommendations on the alfalfa N credit to corn are based on alfalfa stand density, but can the N credit be more accurately predicted based on alfalfa regrowth prior to termination by tillage? Fertilizer N recommendations in Wisconsin combine the two by suggesting an additional 40 lb N/acre credit be given if 8 or more inches of regrowth is present when the alfalfa stand is killed.


Legume N credits are usually higher with fall tillage rather than spring tillage. The longer interval after tillage allows more N mineralization from the alfalfa residue and soil organic matter. Does alfalfa regrowth alter this effect of tillage time? If moving tillage time from spring to fall or incorporating alfalfa regrowth occurring after September 1 increases the N credit by 50 lb N/acre, a corn grower could greatly reduce production costs for first-year corn.


With generous funding from the Minnesota Corn Research and Promotion Council, we will be conducting on-farm research beginning this fall - to investigate the effect of two management factors on the N credit from alfalfa to first-year corn. The two management factors that we will investigate are:  i) alfalfa regrowth (alfalfa regrowth after September 1 removed prior to tillage vs. incorporated with tillage); and ii) the timing of tillage to terminate the alfalfa stand (fall vs. spring).


We are currently looking for alfalfa/corn growers in southern Minnesota who are interested in being involved in such research, and that have a 3- or 4-year-old alfalfa field with a stand of 2 or more plants/sq. ft. that will be terminated after this growing season. The land area required for this research is approximately 1.5 acres. Ideally, fields would be located within 2.5 hours of the Twin Cities.


This research would require help from the growers to establish the regrowth treatments in the fall of 2009. It would also require help from the growers to establish the tillage timing (alfalfa termination) treatments in the fall of 2009 and again in the spring of 2010. After spring plowing in 2010, growers would prepare the seedbed, plant corn, and control weeds with their equipment, using the same production practices that are used within the rest of the field (except that manure and N fertilizer cannot be applied in the experimental area). We will take care of N fertilizer application and crop harvest in the experimental area. Cooperating growers will receive $500 in the fall of 2009 and an additional $500 in the fall of 2010.


Growers with suitable alfalfa fields that are interested in being involved with this on-farm research project should contact Jeff Coulter (612-625-1796 or or Michael Russelle (612-625-8145 or


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