Organic Amendments Addition on Altering the Sorption, Vertical Movement and Leaching Behavior of Herbicides in Soil

Herbicides are applied indiscriminately to achieve maximum weed control in agricultural production which might contaminate the food chain through the bio-augmentation of residue concentration in soil. One of the management suggested to overcome the herbicides contamination is treating with various organic amendments. Hence the laboratory column leaching and sorption experiments were conducted in Tamil Nadu Agricultural University (TNAU), Coimbatore to investigate the leaching behavior of herbicides viz., pendimethalin, atrazine and imazethapyr in soil as influenced by various organic amendments applied @ 5t/ha viz., FYM, vermicompost, composted coir pith, maize crop residue and biochar. Leaching experiment was conducted using PVC columns of 45 cm length and the sorption study was conducted using different concentrations of chosen herbicides as per OECD guidelines. Results showed that leaching and movement behavior of the studied herbicides in soil was modified by the applied organic amendments particularly the biochar and maize crop residue. Biochar treated soil retained 29.76, 40.20, and 38.07 percent of the applied pendimethalin, atrazine and imazethapyr respectively in surface 0-15 cm depth and reduced its movement to lower depths and to leachates. Herbicides adsorption was higher with biochar and is indicated by the Koc values of 225, 184 and 22 mg/L for pendimethalin, atrazine and imazethapyr respectively and was followed by the maize crop residue. It is concluded that the application of biochar @ 5t/ha as organic amendment is efficient in decreasing the herbicides movement viz., pendimethalin, atrazine and imazethapyr and modifying their sorption and leaching potential to groundwater.