Shattercane Control in Narrow‐Row Soybeans 1

Much shattercane [ Sorghum bicolor (L.) Moench] infested land is being rotated from sorghum [ Sorghum bicolor (L.) Moench] or corn ( Zea mays L.) to soybeans [ Glycine max (L.) Merr.] in order to selectively control this weed increaser with herbicides plus cultivation. Some farmers became interested in growing these soybeans in narrow‐rows and eliminating cultivation in order to take advantage of higher yields of drilled soybeans. Thus, field experiments were designed to determine the feasibility of narrow‐row soybean production on a Colo silty clay loam (Cumulic Haplaquolls) infested with a forage sorghum [ Sorghum bicolor (L.) Moench] during 1974‐78 at Lincoln, Neb. Forage sorghum showed competitiveness similar to shattercane without soil persistence of seed, and preplant herbicides were selected for shattercane toxicity and soybean tolerance. Seven of 18 herbicide treatments applied preplant and soil‐incorporated gave better than 95% average weed control, but none gave 100% control. Many preplant herbicides selectively controlled weeds in soybeans with little or no soybean injury or stand loss. These same herbicides facilitated economical, narrow‐row soybean production without cultivation in shattercane infested fields. However, a limited amount of shattercane seed was produced each year; so some method of controlling these weed escapes will be needed if shattercane is to be eradicated from soybean fields.