Abstract

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The studies on the effects of the herbicide (atrazine, glyphosate and gramaxone) on soil physico- chemical properties was carried out between the months of August 2022 to January2023. Two sites forest and a garden were selected in Federal Polytechnic Mubi, Adamawa State, Nigeria using randomized complete block design (RCBD). The herbicides had significantly increased the amounts of soil organic carbon, organic matter, pH, sodium, potassium, bulk density, particle density, percentage moisture, available phosphorus and percentage nitrogen at p< 0.001 level of confidence, at same time lowering the values of available phosphorus (6.27 ppm), magnesium (2.19 ppm), sodium (0.36 ppm), potassium (2.10 ppm), iron (0.25 ppm) and manganese (7.21 cmol k -1). Bacterial species isolated at the study sites showed Pseudomonas aeruginosa, Pseudomonas putida, Bacillus subtilis, Bacillus sphaericus, Staphylococcus aureus, Klebsiella, Escherichia coli, Azotobacter nigricans, Flavobacterium aquaticum, Micrococcus loteus, Salmonella typhimurium, and Proteus vulgaris. Forest soil was found having the highest percentage of (52.75 %), while, the garden (47.25 %) of soil bacterial isolates. The herbicides caused a decrease in the soil bacterial counts and that gramaxone at higher dosage caused the highest decrease while glyphosate the least. Garden soil was found as having higher bacterial counts compared with the forest. Month of November/120th day (157.5x10-3 ±13 cfu/g) had the highest counts, followed by August, while December and January had the lowest which may be attributed due to seasonal variation from rainy to dry season.

Keywords: Herbicide, soil, biodegradation, absorption, bacteria