Enzymatic activities and microbial biomass in black soil as affected by azoxystrobin

As a high-efficiency and broad-spectrum new fungicide, azoxystrobin has been widely applied on various crops. However, little is known about the effect of azoxystrobin on microbial biomass and enzymatic activities in black soils. A laboratory experiment was conducted to study the impact of azoxystrobin application at different concentration levels (0, 0.1, 1.0 and 10.0 mg kg⁻¹) on cultivable microbial biomass and soil respiration in black soil. Urease, protease, dehydrogenase and catalase activities were also monitored on days 7, 14, 21 and 28. The results showed that the populations of cultivable bacteria, fungi and actinomycetes were seriously inhibited when the incubation time was over 7 days. The variation in soil respiration showed similar inhibition tendencies on the 14th, 21st and 28th days. A significant increase in the activity of catalase in black soils in response to higher levels (1 and 10 mg kg⁻¹) of azoxystrobin was observed only on the 28th day. Azoxystrobin had similar significantly negative influences on the activities of urease, protease and dehydrogenase; however, the level of inhibition depended on the doses of azoxystrobin and the time after its application.