The behavior of pesticide in soils: the influence of various environmental factors on the degradation of Metribuzin

Like other herbicides, Metribuzin may be dissipated in the soil via its degradation through chemical and biological processes. Soils represent a complex biological, chemical and physical system. The degradation of herbicides is influenced by many factors as: concentration, diffusion, adsorption-desorption and climatic factors. Soil microorganisms contribute to the rapid degradation of metribuzin. In the present experiment carried out on two soils from Lebanon, deamination of metribuzin in the sandy loam soil to its deaminometribuzin derivative, was basically a result of biological activity. In the clay soil, the first metabolite diketometribuzin, was a result of oxidative desulfuration while diketo-deaminometribuzin is the product of reductive deamination. The two soils represent major differences in the pesticide transformation processes. Photodecom-position on the soil surface and in aqueous media is also an important process in the degradation of metribuzin. The increase in soil organic matter enhances degradation.