Effect of Soil Moisture on Persistence of Sulfosulfuron under Laboratory Conditions

The effect of different soil moisture levels was studied on the persistence of sulfosulfuron using maize as a test crop. Plant height and fresh weight of maize decreased significantly with corresponding increase in sulfosulfuron concentration at all the incubation periods and moisture contents. At 60 days incubation the plant height of maize increased by 28.4, 31.2 and 45.1% at 50, 75 and 100% moisture levels as compared to 0 days. Similarly the increase in fresh weight of maize at 120 days was 41.1, 48.6 and 55.2% at 50, 75 and 100% moisture levels respectively. There was an increase in GR₅₀ value of sulfosulfuron with increase in incubation period at each moisture level. At 120 days of incubation the GR₅₀ at 100% moisture was approximately 2.56 times higher than that at 50% moisture. Maximum and minimum loss of herbicide was recorded at 100% and 50% moisture content respectively. After 120 days 6.2, 5.1 and 2.4% of herbicide remained in the soil at 50, 75 and 100% moisture levels respectively. At 100% moisture 50% of sulfosulfuron was degraded within 13 days while it took about 15 and 21 days at 75 and 50% moisture respectively. The persistence of sulfosulfuron decreases with increase in moisture level.