Abstracto

Adsorption and Degradation of Herbicide Halosulfuron-methyl in Indian Soils

Chirukuri Rajasekharam and Atmakuru Ramesh

Halosulfuron-methyl is a new, low rate, sulfonylurea herbicide that is being promoted for annual broadleaf and gramineal weed control; however, there is a lack of published information on its behavior in soils. The adsorption and degradation of Halosulfuron-methyl by four soils were measured using a batch equilibrium technique. The soil sorption coefficient Kf, the soil organic carbon sorption coefficient Koc and Herbicide degradation DT50 are the basic parameters used for describing the environmental fate of the herbicide. The results showed that the Freundlich equation fitted its adsorption well, and the Frendlich constant value (Kf) ranged from 1.1-6.1. Soil organic carbon coefficient Koc ranged from 105-173. Soil pH, organic matter (OM), and clay content were the main factors influencing its adsorption. Adsorption was negatively correlated with pH 6.0-8.0 while positively correlated with OM and clay content. Persistence of Halosulfuron-methyl conducted in all the 4 kinds of soil shows the DT50 at 8.1 to 10.9 days. The sorption coefficient (Koc) and half-life (DT50) were determined by combining the values of Koc and DT50, and the mobility of residues of Halosulfuron-methyl in soil was calculated using GUS (Ground water Ubiquity Score) equation. The GUS values were found to be less than 1.9 in all the types of soils studied.