Control of Weeds in Narrow‐Row Soybeans1

Abstract

AbstractImproved weed control systems in the absence of row cultivation were researched in order to take advantage of higher yields of soybeans [Glycine max (L.) Merr.] grown in narrow rows. Weed control systems, utilizing 13 pre‐emergence and two postemergence herbicides or herbicide combinations and the rotary hoe, were devised for the production of narrow‐row soybeans at two locations in eastern Nebraska during 1972–74. Experiments were conducted on a Sharpsburg silty clay loam (Typic Argiudoll) at Lincoln and on a Judson clay loam (Cumulic Hapludoll) at Concord, Neb. Research was undertaken to reduce labor, energy, and production costs while attempting to achieve better weed control, earlier ground cover, and higher soybean yields. Selective control of grass weeds in soybeans was more readily accomplished than the control of such large‐seeded broadleaf weeds as Pennsylvania smartweed (Polygonum pensylvanicum L.), sunflower (Helianthus annuus L.), and valvetleaf (Abutilon theophrasti Medic.). Reduced application rates of grass herbicides were used successfully in narrow‐row soybeans. Weeds were controlled in soybeans, with a number of herbicide treatments, with only minor early crop injury and no stand reduction. Average weed yields from all herbicide treatments were markedly lower than those on weedy check plots, but were not significantly different from the hand‐weeded plots. All herbicide treatments except one produced average soybean yields that were equivalent to those on the hand‐weeded plots. Available weed control systems can eliminate the need for cultivation in narrow‐row soybean production. Such systems of weed control should increase soybean yields, reduce production costs, require less labor and fuel, and improve ground cover needed to protect our soil from wind and water erosion.