Effects of Paraquat and Atrazine on Soil Microbial Activities and Soil Mineral Content

Application of herbicides to remove weeds is now the most common method in mechanized agriculture. This study tested the consequences of using herbicides to kill weeds. Viable counts of bacteria and fungi were determined. Microbial activities such as microbial respiration, microbial biomass carbon, dehydrogenase activity, acid phosphatase activity and organic matter were also analyzed. Physicochemical components of the soil were also analyzed. As the concentration of paraquat herbicide applied to the soils increased from 4 ml to 12 ml the Pseudomonas spp became more dominant. Aspergillus spp were more dominant among the fungal species showing their ability to multiply and utilize paraquat as nutrient source. As the concentrations of paraquat and atrazine increased the microbial activity values reduced. Treatment of soils with atrazine and paraquat resulted in significant (P≤0.05) reductions in the pH, acidity (H+), Na, K, Ca and Mg values of the soil samples This study has shown that continual application of herbicides to soils caused significant changes in soil microbial activity.