Dissipation kinetics of dimethoate and malathion residues on tomato-cropped soil

A supervised field trial was carried out in the Department of Entomology, Dr YS Parmar University of Horticulture and Forestry, Nauni, Solan, Himachal Pradesh during the year 2016. The dissipation pattern of dimethoate and malathion residues was estimated on tomato-cropped soil using dispersive QuEChERS technique and detected with a gas chromatograph (SHIMADZU-2010) coupled with a flame photometric detector (FPD). Dimethoate and malathion were sprayed on tomato fruit crop at 200 and 400 g ai/ha and 750 and 1, 500 g ai/ha respectively. The analysis showed that the average initial deposit of 0.169 mg/kg in tomato-cropped soil was found to be below the level of determination after 3^rd day of treatment of dimethoate 200 g ai/ha. On the contrary dimethoate application of 400 g ai/ha yielded initial deposits of 0.337 mg/kgin cropped soil which further degraded to 0.121 mg/kgon day 3 of application. The residue was reduced by 64.16 per cent and was not further detected in successive interval on 7^thday. For malathionthe initial residues in soil were 0.280 and 0.505 mg/kgwhen sprayed with750 and 1, 500 g ai/ha. The initial deposit residues were reduced to 66.43 per cent on day 7. Dimethoate residues persisted up to 3 days whereas those of malathion remained for 3–7 days in soil.