ECONOMICS OF JOHNSONGRASS (SORGHUM-HALEPENSE) CONTROL IN SOYBEANS (GLYCINE-MAX)

Field trials were conducted from 1986 to 1988 at Clarkedale, AR, to evaluate selective POST grass herbicides for johnsongrass control in soybeans. Herbicide treatments were trifluralin PPI followed by single and sequential POST applications of fenoxaprop, fluazifop, quizalofop, or sethoxydim. In 1986, sequential applications of sethoxydim and fenoxaprop controlled more johnsongrass 4 WAT than single treatments. In 1987 and 1988, all herbicides except fenoxaprop controlled more than 79% of johnsongrass. The number of johnsongrass stems was reduced by cultural practices and herbicides after 2 yr. The lowest cost of control and the highest average net return over the 3-yr period was obtained with quizalofop.