Ecotoxical Effects And Mechanism Of Excessive Acetochlor And Urea To Eco-system In Phaeozem Cropland

As staple herbicide and nitrogenous fertilizer, acetochlor and urea have been widely used in phaeozem. Single and joint effects and mechanism of excessive acetochlor and urea on eco-system in phaeozem thus were investigated, aimed to provide theory references for continuable agriculture in the area.Acetochlor and high concentration urea were toxic to earthworms,leading their mortality and weight decreasing. Pollutions result in soluble protein content decreased. The activities of SOD and POD rise first reducing by pollutions, and decreased afterward with the higher concentrations. Then, non-reversible damage was induced and deadness happened.Acetochlor and high concentration urea had bad effects on germination, shoot and root elongation and seedling. Soluble protein and chlorophyll contents decreased with the increasing concentration of acetochlor. The activities of SOD and POD rise first reducing by pollutions, and decreased afterward with the higher concentrations. Low concentration of urea could increase soluble protein and chlorophyll contents and activity of SOD and POD, while urea of high concentration would induce the decrease of soluble protein and chlorophyll contents and activity of SOD, increase POD activity. That would destroy cellular membrane, stunt seedling and even wither away.Acetochlor showed various degrees of damage to microorganisms in soil. Effect of low concentration acetochlor could resume in a relative short time, it was contrary when concentrations were high. Soil respiration increased when concentrations of acetochlor and urea were low and decrease with high concentrations.Combined effects were antagonism when concentration of urea was low, while synergism when concentration of urea was high.