Soil, water, grains and straw samples collected from farmer's field were extracted and cleaned-up by using QuEChERS method.Limit of detection (LOD) and limit of quantification (LOQ) were 1.0 and 3.0 ppb. Average recovery experiments at 0.25 and 0.5 ppm fortification level revealed the recoveries of pretilachlor to more than 80%. It was observed that under green manuring, the residues of pretilachlor, dissipated at faster rate than under non-green manuring conditions. The residues were found to dissipate near 100% after 30 days under non-green manuring, whereas residues reached below detection level after 15 days under green manuring. Under non-green manuring, the half life of pretilachlor was 8.9 days whereas, under green manuring, the herbicide attained its half life in 7.3 days. There were no residues in paddy grains and straw.  Low to moderate leaching potential of pretilachlor was observed at lower dose. But higher dose show good leaching in an experiment conducted under lab conditions so as to know the leaching behavior of pretilachlor. Presence of pretilachlor residues above MRL in ground water at five out of seventeen different sites is going to prove an alarming situation for the policy makers before recommending weeds management strategies. Persistence of the residues may be due to indiscriminate use without following good agricultural practices by the farmers or may be due to higher ground water re-cycling through tube-well irrigation.

Estimation of pretilachlor in paddy field and ground water using gc-ms tq

248th National Meeting (2014)

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