HERBICIDE COMBINATIONS FOR PREHARVEST WEED DESICCATION IN EARLY-MATURING SOYBEAN (GLYCINE-MAX)

Field experiments were conducted at three locations in Mississippi in 1995 and 1996 to evaluate labeled and alternative herbicides and herbi cide combinations for weed desiccation prior to soybean harvest. Weeds evaluated included pitted morningglory, hemp sesbania, spotted spurge , common cocklebur, and sicklepod. Soybean yield and harvestable soybe an losses were not affected by preharvest herbicide treatments, spray volume, or surfactant concentration. Soybean moisture was most consist ently reduced by glufosinate compared to the untreated and other herbi cides and herbicide combinations evaluated. Most desiccation treatment s at Stoneville and Brooksville resulted in foreign material similar t o the weed-free check. Glufosinate at 0.84, 1.1, and 1.4 kg ai/ha desi ccated all weeds evaluated 90% or more with no differences among rates . The addition of 3.4 or 6.7 kg ai/ha sodium chlorate to 0.28 kg ai/ha paraquat, 1.1 and 2.2 kg ai/ha glyphosate, or 0.28 and 0.56 kg ai/ha oxyfluorfen increased desiccation of most weeds evaluated, with no dif ference between sodium chlorate rates. In some instances, reducing app lication volume from 281 to 94 L/ha improved pitted morningglory desic cation when 0.28 g/ha paraquat was applied alone. There were no differ ences between 0.25 and 0.50% (v/v) surfactant for most parameters eval uated.