Herbicide combinations for soybean (Glycine max) planted in stale seedbed.
In field trials conducted in Louisiana during 1989-90, the effects were evaluated of non-selective herbicides (paraquat at 420 g/ha, glyphosate at 1120 g and glufosinate at 840 g), applied alone and in combination with herbicides having both foliar and soil residual activity (metribuzin + chlorimuron at 360 + 60 g, metribuzin at 420 g and imazaquin at 140 g), for weed control in soyabeans cv. Centennial, Hartz 6686, Davis, RingAround 606 and Coker 686. Echinochloa crus-galli, when 7-25 cm tall, was controlled by 48-74% with paraquat, 83-87% with glyphosate and 85-91% with glufosinate. In most cases E. crus-galli control was not enhanced by addition of the residual herbicides. When rhizome and seedling S. halepense plants were present, control with glyphosate was 96% compared with 55% with paraquat and 86% with glufosinate. Tank-mixtures of non-selective and residual herbicides generally enhanced the control of Ipomoea hederacea [Pharbitis hederacea], I. lacunosa, Sesbania exaltata (15-30 cm tall) and Sida spinosa (15-18 cm). Soyabean yields in most cases were not increased by the addition of residual herbicides. Yields following glufosinate, applied alone, were 25% greater than those following paraquat, and for all herbicide treatments yields were at least 45% greater than untreated control values.