SULCOTRIONE SOIL PERSISTENCE AND MOBILITY IN SUMMER MAIZE AND WINTER-WHEAT CROPS

Sulcotrione soil persistence in spring maize (Zen mays L.) crops grown on a sandy loam soil was greater at pH 5.5 and 6.0 (soil half-life T1 /2 approximate to 58 days) than at pH 7.1 (T-1/2 = 44 days). Sulcotrio ne was also applied as recommended on a summer maize crop at the five- to six-leaf growth stage, grown on a sandy loam soil. Sulcotrione soi l half-life was 44 days, and the herbicide remained mainly in the 0- t o 5-cm surface soil layer during the cropping period, in spite of the high water solubility and the heavy rains at the end of August; lower sulcotrione concentrations (10-18% of the total during the 2-month per iod after sulcotrione application) were detected in the 5- to 10-cm su rface soil layer. The herbicide was applied pre-emergence to winter wh eat (Triticum aestivum L.) at four sites that differed in their soil t exture and composition: loamy sand, sandy loam, loam and clay loam. Pe rsistence was greater in the soils containing more organic matter. In soils having similar organic matter contents, persistence was lower in the soil containing more sand relative to loam and clay. During the w inter crops, sulcotrione moved down to the 10- to 15-cm soil layer, in spite of the fact that the rains were lower in winter than in summer. Sulcotrione most generally was not detected in the 15-20 cm soil laye r of the maize and winter wheat crops.