During the 1994/95 growing season, a field assay was conducted in Capinópolis, MG, to evaluate the carryover effect of the herbicides imazamox (50 and 100 g/ha), and imazethapyr (100 and 200 g/ha), applied in soybean, to corn and sorghum crops succeeding soybean. Bioassays using sorghum as test-plant were conducted in greenhouse conditions using soil samples collected from plots sprayed with the herbicides in field. Soil samples were collected at 30, 60, 90 and 120 days after application (DAA) of herbicides. One day after soybean harvest, corn and sorghum were also sowed in the field plots previously used for soybean growth, where the herbicides had been applied. The results obtained denote that imazamox had a shorter residual effect in soil, having no influence on the development of the test-plan t at 120 DAA, even when at double the recommended rate. However, imazethapyr appl ied at 200 g/ha (double the recommended rate), inhibited the development of sorghum plants sowed 120 DAA. Under field conditions, sorghum plants sowed after soybean harvest in areas receiving double the recommended rate of imazethapyr evidenced shorter plant height and shorter plant panicle, although having no effect on grain productivity.
Bioassay; persistence; soil residues