Persistence and fate of pesticides in sugarcane soils

Pesticide residue concentrations in sugarcane soils sampled from commercial farms have been determined for the insecticide chlorpyrifos and the herbicides atrazine, diuron, paraquat and trifluralin. Concentrations of these compounds in surface and sub-surface soils measured before the start of a new season were low, indicating that these pesticides did not build up to high levels from historical use. The decline of residues in the soil following fresh applications was followed over time at three different sites with different soil types. This information allowed the assessment of risk periods for possible off-site movement of these compounds. Chlorpyrifos was present in low concentrations in the surface soil (0-25 mm) and posed minimal risk for movement. The herbicides atrazine, trifiuralin, diuron and paraquat were moderately persistent and therefore available for possible off-site movement for some time after application. This information will be useful for providing guidance to the industry on the development of management guidelines for minimising off-site movement of pesticides.