Dissipation Kinetics and Environmental Risk Assessment of Halosulfuron Methyl in the Sandy Clay Loam Soil of Tropical Sugarcane Crop Ecosystem

Abstract

Halosulfuron methyl has label claim for managing the purple nutsedge, Cyperus rotundus in sugarcane, Saccharum officinarum L. Since reports on dissipation kinetics of halosulfuron methyl in tropical sugarcane ecosystem are lacking, we have studied the persistence of the molecule in the sandy clay loam soil at its recommended (67.5 g a.i./ha.) and double the recommended doses. A simple, single-step extraction-cum-cleanup method was adopted to determine the residues of halosulfuron methyl in the soil matrix. The method could provide 95.4 ± 5.7 – 96.7 ± 3.9% recoveries when validated at three levels of fortification ranged from 0.01 to 0.1 µg/g. At the recommended dose, the halosulfuron methyl residues were detected and quantified up to 90 days after treatment (DAT) and they reached below the detectable level (BDL) of 0.01 µg/g on 105th day after treatment. It took two weeks for the herbicide to dissipate to 50% of its initial deposit of 0.288 µg/g. At double the recommended doses, the residues were detected up to 105 DAT and reached BDL on 120th DAT. The half-life of the herbicide was worked out to be 8.85 and 9.12 days at its recommended and double the recommended doses, respectively. Thus, halosulfuron methyl was observed to be a non-persistent herbicide in the sandy clay loam soil of tropical sugarcane crop ecosystem. Halosulfuron methyl was expected to pose low to moderate level of risk to earthworm and the beneficial arthropod at its recommended dose with risk quotient values lies between 0.1 and 1.