الفهرس 
acknowledgmentOnly 14 pages are availabe for public view
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Abstract
some Pesticides are applied in different types of soil in persistence of Pesticides and evaluate their this study. To study their effects on soil enzymes activity (dehydrogenase, phosphatase and urease), Also kinetics of the enzymes were studied. I Three types of soil used (clay, sandy loam and loamy ) were collected from different area having no history of previou during study. Soils were s exposure to pesticides. Soil samples were air-dried and sieved through (<2mm), then thoroughly mixed before using. 1n the experiment of pesticides persistence three replicates were conducted to each treatment in all experiments. Two types of soils were mixed with the tested pesticides carbofuran (nematodcide), methomyl (insecticide) and thiophanate-methyl (fungicide) in recommended dosage as 2, 0.25and 0.5 tg /g soil respectively. Two sets of the experiment were conducted; the 1st set used autoclaved soils, while the other one involved non-autoclaved soils. In each experiment, the pesticides were thoroughly mixed with the soil. The mixture was maintained at the 60% of water holding capacity (W.H.C.) through the period of experiments. Soil samples were incubated at 25± °C for appropriate periods. In soil enzymes activity three types of soil (clay, sandy loam and loamy) were used .Each pesticide was applied at (half RD, recommended dose, and two fold of recommended dose) evaluate the impact of the pesticides on the dehydrogenase, phosphatase and urease activity, In soil enzyme kinetic, each pesticide used in its recommended dose mixed with different types of soil .The results could be summarized as follow: Persistence of carbofuran, thiophanate—methyl and methomyl in non autoclaved and autoclaved soil showed that the pesticides are gradually disappeared with time in both soils. Persistence of pesticides in sandy loam soil was shorter than those in clay soil. The persistence of pesticidesin autoclaved soil was higher than those in non-autoclaved one. This data indicated that the microbial degradation plays a major role in the degradation of the pesticides. The pesticides arranged according to persistence in order as follow Carhofuran >thiophanate-methyl methomyl in all soils.
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