Strip intercropping of grain sorghum/soybean in irrigated and rainfed environments

A strip-intercropping system of grain sorghum [Sorghum bicolor (L.) Moench] /soybean [Glycine mar (L.) Merr.] has potential to reduce soil erosion comp ared with a 2-yr rotation of large monoculture fields of these two crops. O ur objective was to evaluate productivity and returns in a grain sorghum/so ybean strip-intercropping system under irrigated and rainfed environments i n eastern Nebraska. Crops were grown in alternating 20-ft. strips in a nort h-south orientation on a Sharpsburg silty clay loam (fine, montmorillonitic , mesic typic Argiudoll). A full-season grain sorghum hybrid was grown with soybean cultivars of different maturity groups. Combine-harvested yields o f the two border rows of grain sorghum and soybean were compared with the m iddle four rows of each crop to determine border effects. Under irrigation, grain sorghum yields in the outside two rows increased in 4 of 5 yr, a max imum of 21 bu/acre in 1986 and 1989, and 5-yr average of 9 bu/acre. Under r ainfed conditions, grain sorghum border row yields were less consistent, av eraging 2.5 bu/acre higher. Soybean yield reduction in border rows was vari able, averaging 5 bu/acre for rainfed and 3 bu/acre for irrigated condition s. Soybean cultivar and planting system had limited effect on either sorghu m or soybean yields. This system may he a useful alternative cropping patte rn to reduce long-term soil erosion, a valuable result for society.