Effect of fungicides and bioagents on rhizosphere microbial population, microbial biomass carbon and dehydrogenase activity in soybean (Glycine max L. Merrill) soil

Abstract

The use of fungicides in agriculture, to protect plants from soil borne pathogens, is a common practice. However, there is a dearth of information on the side effects of fungicides on key soil ecological and microbial processes. Effects of different fungicides on soil microbial population, microbial biomass carbon and dehydrogenase activity were investigated. Fungicide effects on bacteria, fungi and actinomycetes were determined on the basis of their growth in respective medium. The population of fungi declined significantly while bacteria and actinomycetes population showed non-significant effect. Most of the fungicides had favorable effect on bacterial population in comparison to the control. Maximum reduction of 21.9 percent in fungal population was found with the use of Trichoderma viride. The application of fungicides and bioagents through seed treatment did not have significant effect on the actinomycetes population in rhizosphere soil. Application of most of the fungicides resulted in increase in microbial biomass carbon and dehydrogenase activity. Among the treatments, application of Pseudomonas fluorescens registered highest microbial biomass carbon and dehydrogenase activity.