Weed Management Strategies for No-Till Soybean (Glycine max) Grown on Clay Soils

Abstract

Weed management strategies are needed for no-till soybean grown on clay soils. The effect of several weed management strategies on weed biomass, soybean yield, and gross return were evaluated in 1993, 1994, and 1995 on clay soils at two locations in southern Ontario. Soybean seeds were planted in narrow (19 cm) and wide (76 cm) rows with or without a rye cover crop. Herbicide treatments included glyphosate alone, glyphosate followed by imazethapyr + metribuzin applied PRE, and glyphosate followed by acifluorfen + bentazon applied POST. Two additional treatments with interrow cultivation were included in the wide-row soybean plots with glyphosate and glyphosate + PRE treatments. A nontreated check plot without rye was also included. Presence of a cover crop did not affect weed biomass or soybean yield. The glyphosate + broadcast PRE treatment provided the most consistent weed control both in narrow- and wide-row soybean. The weed control in this treatment ranged from 92 to 100%. The other treatments provided variable weed control across years and locations. The narrow- row plots with glyphosate + broadcast PRE treatment provided the most consistent soybean yields that were generally higher than the other treatments and ranged from 2,560 to 3,420 kg/ha. Soybean yields varied across locations and years in other treatments. Similar weed control and soybean yields were obtained with banded PRE herbicide + interrow cultivation and PRE treatments; however, herbicide use was 60% lower in banded PRE herbicide + interrow cultivation treatment. Narrow-row soybean averaged 27% higher gross returns than wide-row soybean for all broadcast herbicide treatments. Narrow-row soybean with PRE herbicide provided the highest gross returns. No-till soybean in narrow rows with preplant glyphosate and broadcast PRE treatment was the most risk-efficient weed management system on clay soils.