| Abstract: | A field trial was conducted in 1996 and 1997 to control speargrass (Imperata cylindrica (L) Raeuschel) for soybean production. The treatments comprised four levels of glyphosate, 1.08, 1.44, 1.80 and 2.16 kg ha−1, applied pre‐tillage and followed by one hoe‐weeding (HW) at 6 weeks after planting (WAP); fluazifop‐butyl, 0.125, 0.25 and 0.375 kg ha−1, at 3WAP; 1HW at 3WAP; 2HW at 3 and 6WAP; and an unweeded control. Glyphosate and fluazifop‐butyl controlled 57–85% and 51–83% respectively of I cylindrica compared with 64–67% by traditional hoe‐weeding. The highest grain yield (1.88 t ha−1) was obtained from plots treated with glyphosate (1.44 kg ha−1) + 1HW. The highest profit, however, was obtained with fluazifop‐butyl. It was unprofitable to apply glyphosate at rates higher than 1.44 kg ha−1 to control I cylindrica at 30 cm foliage. © 2000 Society of Chemical Industry |
