Wednesday, 9 November 2005
7

Doublecrop Small Grain-Snap Bean in Rotation with Corn or Soybean to Achieve Economic and Environmental Goals.

Jeffrey Strock, University of Minnesota - SWROC, 23669 130th St., Lamberton, MN 56152-1036, Michael Russelle, USDA-ARS and Department of Soil, Water, & Climate, University of Minnesota, 1991 Upper Buford Circle, Borlaug Hall, St. Paul, MN 55108-6028, Carl Rosen, Department of Soil, Water, & Climate, University of Minnesota, 1991 Upper Buford Circle, Borlaug Hall, St. Paul, MN 55108, Jeffrey Apland, Department of Applied Economics, University of Minnesota, 231 Classroom Office Building, 1994 Buford Ave., St. Paul, MN 55108, and Tom Rabaey, General Mills / Green Giant, 1201 N 4th St., Le Sueur, MN 56058.

Farmers often are not interested in planting cover crops because these crops do not provide income and involve extra expense. Cover crops also frequently fail to achieve environmental goals in cold regions. Winter wheat (Triticum aestivum L.) and spring barley (Hordeum vulgare L.) may be managed as cover crops and yet produce marketable commodities. The objective of this experiment was to evaluate drainage discharge and nitrate-nitrogen (N) losses through subsurface drainage, and breakeven grain yield of corn (Zea mays L.) or soybean [Glycine max (L.) Merr.] in rotation with winter wheat- or spring barley-snap bean (Phaseolus vulgaris L.) doublecrop. Preliminary results indicate that small grain-snap bean doublecropping reduced subsurface drainage discharge by 7 to 14% compared with corn and soybean. Flow-weighted mean nitrate-N concentrations during tile flow were corn and soybean = 23 mg L-1, barley-snap bean = 15 mg L-1, and winter wheat-snap bean = 13 mg L-1. Nitrate-N losses in the subsurface drainage water from the winter wheat- and barley-snap bean doublecrop were about 3.8 and 3.1 times lower, respectively, than from corn and soybean. Using net operating returns for the dominant cropping system in the region, a corn and soybean rotation, breakeven snap bean yields were computed for a range of farm-gate snap bean prices. The estimated breakeven snap bean yields compare favorably to yields from experimental trials when evaluated at prices observed in other regions. This system could be adopted in Minnesota to meet current snap bean demand. The approach used here could be used to evaluate other high-value crops planted after small grain harvest to maintain profitability while increasing crop diversity and improving water quality.

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