Multiple Cropping Systems in Small Grains in Northeast Nebraska

Abstract

Relay intercropping soybean [Glycine max (L.) Merr.] into small grain has been suggested as a way to move multiple cropping further north, or as an alternative to conventional doublecropping in the lower Midwest. Our objective was to compare conventional monocrop soybean, grain sorghum [Sorghum bicolor (L.) Moench], and forage sorghum with relay intercropping and doublecropping in oat (Avena sativa L.) or winter wheat (Triticum aestivum L.). Field experiments were conducted from 1982 through 1986 in northeast Nebraska at 42.2° latitude, 97° longitude, further north and west than the usual multiple cropping regions. Skip-row spacings every fourth drill row were left in the small grain where relay intercrops were later planted in 28- or 30-in. spacings. All doublecropping followed removal of oat or winter wheat for forage, while with relay intercropping, cereals were harvested for grain. Weed control in a relay intercropping system also was investigated. Averaged over the eight location-years, small grain yields with relay intercropping were reduced 34% compared to solid-seeded monoculture yield because of wheel traffic damage and the skip-row spacing effect. Average soybean yield with relay intercropping and doublecropping was 28% of conventional monoculture yield and relay intercropping was never superior to sequential doublecropping. Similar results were found with grain sorghum as relay intercropping and doublecrop yields averaged 15% of conventional grain sorghum. Relay intercrop and doublecrop forage sorghum yielded 37% and 54% of monoculture forage sorghum. Relay intercropping may make it possible at more northern latitudes to harvest cereal crops for grain rather than for forage as is usually done in a double-crop system, which would be advantageous for cash grain producers. Satisfactory weed control was achieved in the relay intercrop system by applying herbicide on the green wheat or oats plus row banding herbicide at crop planting. Economic analyses indicated that monocrop systems generally provided greater returns than relay intercrop or doublecrop systems. Returns in the doublecrop system were more favorable than with relay intercropping, particularly with the wheat-forage sorghum crops. Relay intercropping requires that many cultural practices be meshed for successful results.