The Influence of Soil Microorganisms and Bio- or -Organic Fertilizers on Dissipation of Some Pesticides in Soil and Potato Tubers

Abstract

The influence of soil microorganisms, biofertilizer and compost fertilization on the persistence of the two organphosphorus insecticides, chlorpyrifos, ethoprophos and carbamate insecticide, carbofuran were studied under semifield experimental conditions. Residue analysis of the initial samples of the three applied pesticides, chlorpyrifos, ethoprophos and carbofuran was relatively high (68.3, 76.0 and 80.9 ppm, respectively) in uncultivated, unfertilized and unsterilized soil. These amounts were decreased to 10.12, 14.6 and 12.0 ppm showing 85.18, 80.79 and 85.17% loss, respectively at 6 weeks after treatments. The initial deposits of these pesticides in po- tato cultivated soils (control) were 70.77, 74.17 and 81.17 ppm, respectively, graduate dissipation of tested pesticides was noticed through the successive intervals. At the end of the experimental period, residues detected revealed 93.0, 91.5 and 94.37% loss, respectively. Addition of certain bioactive (microbal and compost ) amendments was able to induce the pesticide degradation in the contaminated soil (the highest degradation levels was noticed in biofertilized soil, > 99.99, 99.33 and 96.11%). On the other hands, obtained data clearly showed that microorganisms living in soil play role in pesticide biodegradation. In other words, the percentages of loss of chlorpyrifos, ethoprophos and carbofuran residues were 86.35, 83.91 and 82.32% in sterilized soils, respectively, at 6 weeks after treat- ments. Obtained data indicated also, the residual values of tested insecticides on or in potato tubers were more than the maximum residue limits (MRL) in all treatments, this means that the tested insecticides have a translocation and accumulating properties in potato tubers.