Dissipation of Pendimethalin in Soil Under Direct Seeded and Transplanted Rice Field.

Abstract

The dissipation of pendimethalin applied in direct seeded rice (DSR) and transplanted rice (TPR) field at 1.0 and 2.0kg a.i. ha-1 followed biphasic first order kinetics (R2 > 0.91) and was comparatively faster under flooded TPR than DSR. The half-life (DT50) of pendimethalin in the soil ranged from 2.22 to 2.80days in the initial phase and 23.51 to 24.66days in the final phase in TPR for both application rates. However in DSR, DT50 varied from 3.67 to 4.35days in the initial phase and 34.19 to 34.99days in the final phase. Residues of pendimethalin in soil samples analyzed by HPLC and GC-MS/MS were below the detection limit (< 0.003µgg-1) for both the application rates in DSR and TPR whereas 0.003-0.009µgg-1 and 0.003-0.008µgg-1 residues of pendimethalin were found in rice grain and straw samples, respectively.