Impact of atrazine on soil microbial properties: A meta-analysis*

Atrazine is a biotoxic long-residing herbicide whose toxic effects on soil microorganisms have attracted wide-spread attention. However, previous studies on the effects of atrazine on soil microorganisms have yielded highly variable results. Therefore, a meta-analysis using a database containing 1141 data points from 39 peer-reviewed papers was conducted to illustrate the response of soil microorganisms to the application of atrazine. The results showed that the application of atrazine significantly increased soil microbial biomass and respiration by 8.9% and 26.77%, respectively, and decreased soil microbial diversity and enzyme activity by 4.87% and 24.04%, respectively. In addition, mixed-effect models were used to explain the influence of moderator variables, including water holding capacity, temperature, pH, organic carbon content, atrazine concentration, duration, and soil texture, on the results to help account for inconsistent conclusions. It was found that soil microbial biomass was significantly positively correlated with temperature, organic carbon content, atrazine concentra-tion, clay content and silt content, while it was negatively correlated with pH and sand content. Soil microbial respiration was negatively correlated with pH and positively correlated with atrazine concentration. Soil mi-crobial diversity was positively correlated with water holding capacity, pH, silt content and sand content, and negatively correlated with organic carbon content and clay content. Soil enzyme activity, the indicator that showed the largest decrease after atrazine application, was significantly positively correlated with water holding capacity, temperature, organic carbon content, and herbicide concentration; it was negatively correlated with soil pH. On the basis of these analysis results, we recommend that atrazine should not be allowed to persist in alkaline sandy soil for long periods of time, as this can result in atrazine having a significant negative impact on soil microorganisms.