Effects of an organophosphate (glyphosate) and a quaternary ammonium (paraquat) herbicides formulation on soils’ culturable bacterial and fungal populations
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Date
2022
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International Research Journal of Biological Sciences
Abstract
Herbicides play significant roles in weed management and contribute immensely to increase in productivity in agronomy system. However, its continuous application could have some dire effect on non-target soil microbiota. Therefore, this study assessed the impact of glyphosate and paraquat herbicides on soil culturable bacterial and fungal population. The loamy composite soil samples of forest reserve, Owena, Ondo State, Nigeria were used for the experiment. Each of the herbicide formulation was applied at the concentration rates ranged from half of the field recommended rate (0.5FR), the recommended rate (FR), two, four, and eight times the recommended rate (2, 4 and 8) FR respectively. The treatments were replicated thrice and arranged in complete randomized design, while the untreated soil samples serve as control. The standard pour plate technique was used for the enumeration of bacterial and fungal colonies after 5, 10, 15, 20, 25, 30 and 35 days of exposure. The findings showed that the glyphosate pesticides formulation applied at concentration range of 0.5 to 2FR significant stimulate bacterial populations of the soil samples while the fungal populations was not affected at the same concentration. However, the treatments at higher doses (4FR and 8FR) significantly reduced the number of bacterial and fungal counts of the soil samples. For paraquat treated soils, the treatment rate below the double recommended field rate did not have any significant effect (p > 0.05) on both bacterial and fungal populations. While the increases in inhibitory effect were observed with corresponding increases in paraquat application rates in the soil samples.