Persistence and residues of pendimethalin in sunßower under long term conservation agriculture system

Field experiment was conducted at Eastern block farm, Tamil Nadu Agricultural University with sunflower to study the persistence and residues of pendimethalin under long term conservation agriculture system. The treatments constituted pendimethalin 30 % EC @ 1.0 kg ha^-1 on 3 DAS and pendimethalin 30 % EC @ 1.0 kg ha^-1 on 3DAS +Hand weeding on 45th day under different conservation tillage practices. Degradation, persistence and residue analysis were carried out for pendimethalin using HPLC. Residues of pendimethalin was analyzed at different periods viz., 0, 15, 45 and 60days after herbicide application and the results revealed that degradation of pendimethalin was found to follow first order reaction kinetics (R² > 0.90) with the half life of 14.84 –20.0 daysIrrespective of tillage practices and weed management methods,. More than 80 % of pendimethalin was dissipated from the soil before harvest. The recommended rate of pendimethalin @1.0 kgha^-1 recorded terminal residues below detectable limit of <0.01 mg kg^-1 in soil and plant parts of sunflower.