Studies on Harvest Time Residue of Pyrazosulfuron Ethyl, a New Generation Herbicide, In Transplanted Rice in the Entisols of Vellayani, South Kerala

Pyrazosulfuron ethyl is a low dose high efficacy herbicide coming under the group of sulfonyl ureas which is effective for controlling a wide range of weeds in low land rice. Field experiments were conducted for two consecutive seasons, i.e., second and third crop seasons at the Instructional Farm, College of Agriculture, Vellayani to estimate the residues of pyrazosulfuron ethyl in soil, rice grain and straw. The experiment was laid out in randomized block design which consisted of eight treatments with three replications. The treatments included four different levels of pyrazosulfuron ethyl (15, 20, 25 and 30 g ai ha -1 ), butachlor (1.5 kg ai ha -1 ), weed free check, unweeded check and hand weeding twice (at 20 and 40 days after transplanting). The results of the experiment revealed a total absence of pyrazosulfuron ethyl in soil, rice grain and straw, i.e., no detectable residue could be observed. Herbicide residue was also determined using cucumber as the test plant. It also revealed that the magnitude of difference in germination per cent and shoot and root length was not significant indicating no adverse effect of applied herbicide. This emphasizes the safety of chemical to soil environment and safety of plant produce for human and animal consumption.