Soil persistence and environmental risk assessment of chlorpyrifos under different organic manuring in the tropical sugarcane ecosystem

Abstract

ABSTRACT Chlorpyrifos has label claim against sugarcane termites and is applied as a soil drench at planting. The organic manures viz., composted coir pith, farmyard manure, press mud and sugarcane trash are also applied at the time of planting mainly to conserve the soil moisture in the tropical environment. The organic manures may have some impact on the persistence of chlorpyrifos in the soil. Hence, the persistence of chlorpyrifos in the manurial soils was studied by employing the single-step sample preparation method and GC-ECD. The initial deposits of chlorpyrifos were 0.325–0.383 µg/g across the treatments involved in the study. The residues were quantified up to 75 days after treatment (DAT) and were below 0.01 µg/g on 90th DAT. The soil half-lives of chlorpyrifos were in the range of 19.8–21.0 days in the manured soils as against 18.7 days in the control soil. Thus, the organic manures applied at planting did not play any significant role in influencing the persistence of chlorpyrifos in the sandy clay loam soil of tropical sugarcane ecosystem. Further, the chlorpyrifos residues were not detected in the sugarcane leaf and stalk, indicating that there was no significant uptake by the plant from the soil. The calculated risk quotient values indicated that the chlorpyrifos residues may pose an unacceptable risk to earthworms during the first week of its application and thereafter, there could be a moderate level of risk in the tropical sugarcane environment.