Degradation of thiobencarb in anaerobic soils

U. B. Cheah and D. G. Crosby

Abstract

The rate and products of degradation of thiobencarb in three types of Californian soils under anaerobic conditions were examined. Dechlorination of the herbicide in the soils was also investigated. A laboratory study using ¹⁴C-thiobencarb in a soil-water aquatic ecosystem showed a slow rate of dissipation of the herbicide in anaerobic soils. Much (37–44%) of the applied thiobencarb remained in the water 45 days after treatment. A steady build-up of the herbicide concentration in the soils was observed, suggesting a slow rate of degradation. Major degradation products were 4-chlorobenzyl alcohol, 4-chlorobenzoic acid and desethylthiobencarb. The formation of dechlorinated thiobencarb, reported to be phytotoxic to rice plants, was not evident in the soils, with or without augmentation with rice straw.

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