Atrazine And The Impact Of Acetochlor On Soil Enzymes

Atrazine and Acetochlor are two kinds of selective herbicides widely applied not only in China but also all over the world for control of weeds in corn, soybeans, and other row crops. As a result of these herbicides used widely and heavily for the last decades, the soil and water contamination by them is more and more of a public concern.The influence of these two herbicides to soil enzymes were chosen for this study. As good representative enzymes integrating the information form mibcrobial status and soil physico-chemical conidtion, which indicate the potential of soil to support biochemical processes and maintain fertility, soil dehydrogenase and catalse were selected. Regarding the dehydrogenase, this research was focused oil the influence of herbicide using and soil properties to its activity - how the enzyme activity responded to herbicide applied separately and jointly, and to the diverse soil conditions. As to the catalase, how it responded to atrazine and acetochlor, and whether it was inhibited by the two herbicides through kinetic measurement, are included in the research interests.From the results of the study, it was concluded that the concentration of herbicide plays an important role and it was the key factor that influences the enzyme activity most among the assessed factors. Atrazine and acetochlor of high concentration (> 5 ug/g soil) stimulated soil dehydrogenase activity significantly (p < 0,01) and intensely, and there was no significant (p >0.05) difference found between the effects of the two herbicides. However, when they were added together to a soil sample, they didn't influence the enzyme activity independently - after applied the herbicide jointly, the value of enzyme activity observed was not equal to the sum of values accounted from the experiment of atrazine and acetochlor applied separately. When the atrazine among the herbicide compound was applied in high dose (the concentration of atrazine is 10 ug/g soil), synergism was observed. It probably resulted from the highhalf-life of atrazine. However, there was no antagonism observed. Despite the herbicides, soil properties could affect the activity of the enzyme as well. However, it is different in absence from presence of herbicide. In absence of herbicide, higher temperature (30C) and lower moisture content of soil (40%MHC) leaded to low dehydrogenase activity. However, Incorporated with herbicide, they worked conversely and potentiation was produced.As to the catalase, it was observed that the enzyme was not sensitive to atrazine or acetochlor. These two herbicides have little influence on the enzyme activity. However, when atrazine or acetochlor was applied in high dose (10 ug/g soil), they both could stimulate catalase activity. The stimulation was not strong and didn't last for long time.From the kinetic measurement, atrazine and acetochlor was able to inhibit the enzyme activity as they could affect the active complex (Enzyme-Substrate). However, it is not convenient for these herbicides to do so in actual environment. Therefore, neither atrazine nor acetochlor will inhibit catalase and the enzyme was not sensitive to these herbicides. Thus was consistent with the results of experiment above. As for the explanation of the stimulation above, it possibly accounts for it that these two herbicides could be used as carbon resource by microbes and thus activated the organism and ultimately enhanced the enzyme activity.Generally speaking, atrazine and acetochlor, applied in recommend dose, didn't have negative effects on soil dehydrogenase and catalase. These herbicides are friendly to environment of soil system.