Effect of Organic Amendments and Soil Texture on Degradation of Atrazine and Metamitron

Of all types of xenobiotics, pesticides such as herbicides play a significant role in soil and water pollution due to their widely usage all over the world. This study addresses the ability of organic amendments to enhance atrazine and metamitron degradation in two herbicide contaminated soils with contrasting textures under laboratory conditions. Soil samples were collected from surface soils with textures of sandy loam and silty clay, from northeastern part of Iran. Initial concentration of herbicides was 50 mgkg-1 soil. Contaminated soil samples were treated by manure, compost and vermicompost at the rates of %0.5 and %2 (w/w). Residual concentrations of atrazine and metamitron were determined by HPLC at the end of incubation periods of 20,40 and 60 d. Residual concentrations of atrazine were 93, 77.8 and 72.4 % of the initial concentration after 20, 40 and 60d incubation, respectively. Residual metamitron concentrations were clearly lower than atrazine. After 20,40 and 60 d., the remaining concentrations of metamitron were 5.8, 2 and 1.2 %, respectively. Organic amendments at the rates of .5 and 2 % showed similar effects on the enhancement of herbicides degradation in soils. However, no significant effect was observed between types of organic amendments. Degradation was clearly affected by soil textures. Residual concentrations of herbicides were higher in sandy loam than in silty clay soil.