Border Effects on Yields in a Strip-Intercropped Soybean, Corn, and Wheat Production System

Abstract

Strip-intercropping of corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] normally results in corn producing a negative border effect on soybean production. This study was conducted to determine whether including a small grain strip between corn and soybean strips could reduce the negative border effects of corn and enhance soybean yields. Corn, soybean, and wheat (Triticum aestivum L.) were grown as strip intercrops (15-ft wide) in a ridge-till system at two locations in southern Minnesota from 1991 through 1994 and were compared with a two-crop corn-soybean system. Rows were oriented east-west at one location and north-south at the other. Soybean yield in the three-crop system was reduced by 17% for the north row adjacent to corn and 8% for the south row next to wheat compared with nonborder east-west rows. In north-south rows, soybean yields were reduced by 21% in the east row next to corn compared with nonborder rows with no yield reduction in the west row next to wheat. In the two-crop corn-soybean strip system, soybean yields were reduced by 34 and 11% in the south and north border rows, respectively, compared with the nonborder rows in east-west rows. In north-south rows, the outside east row yielded 19% less and the west row yielded 21% less than the nonborder rows. Corn yield of the outside north row next to wheat in east-west rows was 6% greater while the south row next to soybean yielded 18% greater than the nonborder rows. In north-south rows, the east outside row next to wheat yielded 23% greater and the west row next to soybean yielded 27% greater than the nonborder rows. In the two-crop system, yield of the outside corn rows was enhanced similarly compared with the nonborder rows in both row orientations. Wheat yield in the 5-ft section next to soybean was 4% greater than the center 5-ft section and 6% greater than the 5-ft section next to corn in east-west rows and 9 and 17% greater in north-south rows. Results from this 4-yr study indicate that wheat planted between corn and soybean strips improved soybean production over the two-crop system without adversely affecting wheat yields. Corn production was enhanced by 9 to 12% in north-south rows and 2 to 7% in east-west rows in both the two-and three-crop strip systems.