Jemrest




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Abstract

Eivazi, F. 2008. Effect of simultaneous application of different pesticides on select soil enzyme activities. JEMREST 5:57-67.

In most farming 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 single and 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. Application of pesticides singularly, with the exception of diazinon, after one hour incubation, inhibited acid, and alkaline phosphatases, sulfatase, and urease activities in soil 1. The activities of glucosiadases, L- asparaginase, and L-glutaminase indicated some reduction but not significant. Effect of pesticide on enzyme activities after 7 days of incubation followed similar trend to one hour incubation for the soil 1. When different pesticides were mixed in combinations and applied to the same soil, acid, and alkaline phosphatases, and urease were inhibited significantly. Multiple-pesticide application in soil 2 inhibited the activities of acid phosphatase, sulfatase and urease at one hour incubation in contrast to control. Slight stimulatory effect with diazinon was observed for acid, and alkaline phosphatases and urease. The findings from this study show that to understand the interactions of pesticides and their effects on soil enzyme, one must take into consideration, not only the direct interaction of the organic compounds with the enzyme molecules, but also the indirect effects derived from the interactions between the pesticides and inorganic/organic moieties in soil.