Postemergence Grass Control with Herbicides Applied at ULV in Paraffinic Oil

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Abstract
Variables affecting ultra-low-volume (ULV) application of herbicides for postemergence grass control in soybeans were evaluated in field experiments from 1988 to 1990. Air-assist applications of clethodim at 2.3 and 4.7 L ha–1were compared with 94 and 187 L ha–1applications with a conventional hydraulic sprayer. Rate of herbicide, volume of diluent, type of diluent, air pressure, and four other herbicides were evaluated. Clethodim at 28, 56, and 112 g ha–1applied in paraffinic oil at 2.3 L ha–1controlled johnsongrass better 10 wk after treatment than equivalent rates applied at 2.3 or 187 L ha–1in water. At 2.3 L ha–1, barnyardgrass control was improved by applying clethodim in paraffinic oil rather than water. Johnsongrass control 10 wk after treatment was better with clethodim at 28 g ha–1applied in paraffinic oil than when applied in soybean oil, cottonseed oil, No. 2 diesel fuel, kerosene, or jet A fuel. Low air pressures of 14 or 28 kPa resulted in better control of johnsongrass and barnyardgrass than higher pressures of 56 and 112 kPa. Clethodim, fluazifop-P, haloxyfop, quizalofop, or sethoxydim were more effective on johnsongrass and barnyardgrass when applied in paraffinic oil than in water at 2.3 and 4.7 L ha–1with an air-assist sprayer.