Absorption of Heptachlor in Potato, Sweet Potato and Onion From Pre-Harvest Sille-Dressing and its Dissipation by Post-Harvest Processings

Side-dressing of heptachlor 5% dust 35 days before harvest of potato, sweet potato and onion resulted in the absorption of residues to th extent of 9 to 11, 13 to 15 and 13 to 16% of 3.72 to 3.85, 5.46 to 5.84 and 11.20 to 11.69 ppm initial deposits from 2.5, 5.0 and 10.0Kg a.i./ha dosages, respectively. The absorption was highest in potato followed by sweet potato and onion. The harvest time residues were considerably in-fluenced by the post-harvest processings. Washing alone removed 22–29% residues from all the crops; washing followed by peeling and cooking reduced 85–93% residues from sweet potato, and 94–100% residues from potato. Dehydration redueced 74–100, 80–100 and 84–100% residues from sweet potato, potato and onion, respectively. Cooking was most effective, and left 0.03 ppm of heptachlor in sweet potato and potato, and no residues in onion at 10.0 Kg a.i./ha.