Enzymatic activities and microbial biomass in peanut field soil as affected by the foliar application of tebuconazole

Field experiments in peanut (Arachis hypogaea L.) soil ecosystem were conducted during the summer seasons (February–June) of the year 2013 and 2014 in black clay soil treated with tebuconazole at field rate (FR), 2-times FR (2FR) and 10-times FR (10FR) as foliar spray to determine the impact of tebuconazole on soil microbial properties and enzymatic activities. Tebuconazole application at FR and 2FR resulted in a short-lived and transitory toxic effect on soil microbial properties and enzymatic activities. The duration of this disturbance was slightly longer at 10FR. Incorporation of tebuconazole in soil resulted in stimulating the soil microbial activity as evidenced by increased ammonification and nitrification rates and increased soil microbial biomass at later stage. However, it was more toxic to soil ergosterol which is the indicator of the presence of viable fungi. Soil enzymatic activities like fluorescein diacetate-hydrolyzing activity, urease, phosphatase and aryl sulfatase are either unaffected or shortly inhibited and then recovered. However, dehydrogenase and nitrate reductase activity decreased more drastically and can be used as valuable indicator to assess the impact of tebuconazole application on soil health. The results indicated that instead of single assays, a broad spectrum analysis of soil microbial and enzymatic activities gives a better insight about the impacts of pesticide on soil health. From this study, it is also concluded that the application of tebuconazole at 10FR had adverse effects on the microbial variables and the effect on long-term application should be studied further.