Deciphering Pyroxasulfone Dynamics in Punjab Soils: Insights into Adsorption, Desorption, and Leaching Behavior

Adsorption-desorption and leaching studies are crucial for understanding herbicide environmental fate and transport, enabling informed decisions regarding their application and risk of groundwater contamination. Batch equilibration technique was used to study the adsorption of pyroxasulfone. Data fitted well to Freundlich (R2 > 0.992) and Langmuir model (R2 > 0.994) suggesting that pyroxasulfone adsorption occurs on both homogeneous and heterogeneous soil sites, involving a combination of monolayer and multilayer adsorption. Adsorption was higher in clay loam soil followed by sandy loam and loamy sand. Thermodynamic parameters revealed that adsorption was spontaneous but became less favourable as temperature increased. Desorption data fitted well into the Freundlich model. A low hysteresis coefficient value indicated greater adsorption and slower desorption of pyroxasulfone. Irrespective of soil type and herbicide application rate, pyroxasulfone leached up to a depth of 0-30 cm and was below detectable limit (<0.01 µg mL-1) in leachates. Pyroxasulfone has highest leachability in loamy sand followed by sandy loam and clay loam. Low leaching potential of pyroxasulfone suggested a reduced groundwater contamination risk, but slow desorption and bound residues indicate soil persistence, potentially leading to phytotoxicity in subsequent crops. Long-term studies across diverse conditions are essential for effective risk management and environmentally sustainable agricultural practices. Adsorption-desorption and leaching studies are crucial for understanding herbicide environmental fate and transport, enabling informed decisions regarding their application and risk of groundwater contamination. Batch equilibration technique was used to study the adsorption of pyroxasulfone. Data fitted well to Freundlich (R2 > 0.992) and Langmuir model (R2 > 0.994) suggesting that pyroxasulfone adsorption occurs on both homogeneous and heterogeneous soil sites, involving a combination of monolayer and multilayer adsorption. Adsorption was higher in clay loam soil followed by sandy loam and loamy sand. Thermodynamic parameters revealed that adsorption was spontaneous but became less favourable as temperature increased. Desorption data fitted well into the Freundlich model. A low hysteresis coefficient value indicated greater adsorption and slower desorption of pyroxasulfone. Irrespective of soil type and herbicide application rate, pyroxasulfone leached up to a depth of 0-30 cm and was below detectable limit (<0.01 µg mL-1) in leachates. Pyroxasulfone has highest leachability in loamy sand followed by sandy loam and clay loam. Low leaching potential of pyroxasulfone suggested a reduced groundwater contamination risk, but slow desorption and bound residues indicate soil persistence, potentially leading to phytotoxicity in subsequent crops. Long-term studies across diverse conditions are essential for effective risk management and environmentally sustainable agricultural practices.