USE OF CARBON TO REDUCE UPTAKE OF INSECTICIDAL SOIL RESIDUES BY CROP PLANTS - EFFECTS OF CARBON ON INSECTICIDE ADSORPTION AND TOXICITY IN SOILS

Laboratory and field tests determined the effect of activated carbon (Norit) on the adsorbance of insecticidal residues to soils, the toxicity of insecticides in soils, and the penetration of these residues into the roots of crop plants. Peas were grown in the laboratory in aldrin, dieldrin, heptachlor, or heptachlor epoxide treated loam soil or quartz sand. Carbon added to soils at 1000 (800 pounds per acre, 3 inches deep), 2000, or 4000 p.p.m. considerably reduced the penetration of the insecticides into the roots and greens of the pea plants. A 96% reduction of the penetration of aldrin into pea roots was achieved with carbon at 1000 p.p.m. in a quartz sand and at 4000 p.p.m. in a loam soil. A 96% reduction of dieldrin or heptachlor and heptachlor epoxide into pea roots was achieved with carbon at 2000 p.p.m. in a loam soil. Carbon in soil prevented the total extraction of the insecticides and reduced the toxicity of the insecticide residues to Drosophila melanogaster Meigen. This binding of the residues to the carbon-soil complex increased with time. Field test results, although similar, were not so striking as in the laboratory. Treatment of the soil with carbon could reduce insecticidal residues in crops to such an extent that a farmer could use a soil of abnormally high insecticidal content. © 1968, American Chemical Society. All rights reserved.