Emurotu M. O. and Anyanwu C. U
The effect of two herbicides (atrazine and butachlor) on soil microbial populations, activities was assessed every fourteen days over a period of seventy (70) days. Soil samples from Kogi State University farm were treated with herbicides at company recommended rates, concentrations above and below the recommended rates. The observed effect of atrazine on bacterial counts at lowest concentration, highest concentration and recommended rates were4.42±0.68, 1.20±0.29 and 3.04±0.36 (x107cfu/g) respectively. Corresponding effect of butachlor were 4.38±0.89, 1.52 ±0.32, 3.34±0.35 (x107cfu/g) respectively. The effects of atrazine on fungal counts at lowest concentration, highest concentration and recommended rates were 16.0±2.3, 1.72±0.41, 9.82±0.54 (x105cfu/g) respectively while corresponding butachlor effects on fungal counts (x105cfu/g) were 17.2±2.9, 5.06±0.46, 13.4±0.4 respectively. Herbicide treatments at recommended and higher rates resulted in decreases in microbial counts. Pseudomonas spp., Bacillus spp. and Flavo bacterium spp. were the most frequently isolated bacteria while Aspergillus niger, Aspergillus flavus, Penicillium spp., Trichoderma spp., Mucor spp. And Fusarium spp. were the most frequently isolated fungi. From this study, butachlor is more microbial and environmental friendly than atrazine. Atrazine was more toxic to microflora.
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