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Abstract

Eivazi, F. 2008. Effect of simultaneous application of pesticides on select soil enzyme activities. JEMREST 5:00-00

In most agricultural practices, several pesticides are applied to a crop during the growing season to control a variety of weeds and insect pests. The present study was undertaken to determine the effect of multiple pesticide treatments on the activities of a - and b -glucosidases, acid and alkaline phosphatases , sulfatase, urease, L-asparaginase, and L-glutaminase in two soils. Five herbicides (alachlor, atrazine, imazethapyr, metolachlor, trifluralin), an insecticide, diazinon, and a fungicide, benomyl were applied in single and multiple systems. The results varied with the particular enzyme and the soil type. In tropical soil, single-pesticide treatment with 10mg of active ingredient per gram of soil after one hour inhibited acid and alkaline phosphatases, sufatase and L-glutaminase activities. Slight stimulatory effect with diazinon was observed for acid and alkaline phosphatases and urease. After 7 days, the trend was similar to one hour incubation. Multiple-pesticide application in tropical soil inhibited the activities of acid phosphatase, sulfatase and urease at one hour incubation in contrast to control. In the case of silty clay soil, acid phosphatase and L-asparaginase activities were significantly suppressed at one hour incubation. However, there was no significant inhibitory effect on enzymes studied after 7 days. L-Asparaginase and L-glutaminse activities were significantly decreased by pesticide mixtures in silty clay soil. Understanding of pesticide effects on enzyme systems must take into consideration not only the direct interaction of the organic compounds with the enzyme molecules, but also the indirect effects deriving from the interactions between the pesticides and inorganic/organic moieties.