INFLUENCE OF SMALL-GRAIN CROPS ON WEEDS AND ECOFALLOW CORN (ZEA-MAYS)

Spring small grains were not as competitive with barnyardgrass and witchgrass as winter wheat. Winter wheat grain yields were greater than spring barley or spring wheat in 1986, 1987, and 1988 and oat in 1986 and 1988. Barnyardgrass, stinkgrass, and witchgrass control with glyphosate plus 2,4-D plus atrazine at 0.6 plus 0.8 plus 1.7 kg ha(-1) was usually less when the herbicides were applied to stubble of spring small grain versus winter wheat due to the advanced weed growth at treatment. Barnyardgrass and witchgrass were more difficult to control than stinkgrass, redroot pigweed, tumble pigweed, kochia, and tumble thistle. No-till corn planted into winter wheat stubble had fewer barnyardgrass and witchgrass than corn planted into spring wheat stubble. The addition of metolachlor plus atrazine at 1.7 plus 0.6 kg ha(-1) eliminated differences among small grain cultivars in weed control in corn. Corn grain yields from winter wheat plots were greater than other small grains in 1989 because of better weed control and more crop residue.