Field Studies on Persistence of Pyrazosulfuron-Ethyl in Soil, Ground Water and Residues in Transplanted Rice

Field experiment was conducted at Zonal Agricultural Research center, Kathalagere, during Kharif 2008. To study persistence and residues of pyrazosulfuron-ethyl in soil and ground water in transplanted rice ecosystem were estimated using HPLC technique. Pyrazosulfuron-ethyl was applied at 25 g a.i. ha^-1 and 50 g a.i. ha^-1 with and without addition of recommended farm yard manure in transplanted rice. The study revealed that the residue of pyrazosulfuron-ethyl in soils ranged from 0.0103 and 0.0199 mg kg^-1, respectively with FYM at recommended and double the recommended dose on 2^nd day of application. And without FYM the residues were 0.0116 and 0.0229 mg kg^-1, respectively. The residues were detected up to 35 days only. The half-life of pyrazosulfuron-ethyl ranged from 16.6 to 21 days. The results revealed that the residues of pyrazosulfuronethyl were below the detectable level in the post harvest soil, paddy grain and straw. No residues of pyrazosulfuron-ethyl were detected in ground water up to two weeks after the application of pyrazosulfuron ethyl. After two weeks the residues were detected in ground water collected from both the piezometers which were applied with recommended and double the recommended dose of pyrazosulfuron-ethyl. The residues ranged from 0.0071 to 0.0042 mg kg^-1 between 21^st and 28^th day, respectively, after which the residues were below the detectable level both at recommended and double the recommended level of application. A maximum of 0.0154 mg kg^-1 on 21^st day and minimum of 0.0023 mg kg^-1 of pyrazosulfuron ethyl residues on 35^th day were detected in the underground water.