. On day 70, 40.5e46.2% of the
chlorpyrifos remained in non-sterilized soils in the three soils
investigated compared to67.5e72.1% in sterilized soils. Half-lives in
the sterilized soils ranged between 173 and 256 days reflecting 2e
3-fold slower degradation compared to non-sterilized soils. The
half-lives of chlorpyrifos in sterilized soils were in the order of
Semongok (256 days) > Tarat (182 days) > Balai Ringin (173 days).