Abstract

Objective: To determine cowpea rhizosphere microorganisms with phosphate solubilizing potential in a soil treated with glyphosate. Methods: Four different concentrations of glyphosate herbicides (0.00, 0.50, 1.00, and 3.00) were assayed. Cowpea seedlings were planted and later harvested after 30 days of germination. Microorganisms from rhizosphere treated with glyphosate were cultured and identified using selective media Wakesman A and B agar. The activity of isolates were evaluated by Tricalcium phosphate solubilizat ion and screening for phosphatase in a Pikovskaya medium.. Results: Bacillus cereus, Bacillus subtilis, Micrococcus luteus, Pseudomonas aeruginosa, Proteus mirabilis, Bacillus pumilis, Staphylococcus aureus, Aspergillus flavus, Rhizopus nigrifican, and Aspergillus saprophyiticus were obtained from the glyphosate treated soil. There was decrease in the bacterial and fungal population in the rhizosphere as glyphosate concentration increased. The concentration of the solubilized Tricalcium phosphate ranged from 42.48 to 515.78gl-1. Micrococcus luteus, Bacillus subtilis, Proteus mirabilis, Aspergillus flavus, Aspergillus saprophyticus isolated at the different concentrations of glyphosate have increased phosphate solubilization with reduction in their pH. Proteus mirabilis showed the highest phosphatase activity (23.157mM/min/ml) at 30hrs and Aspergillus saprophyticus showed highest phosphatase activity (35.263 mM/min/ml) at 72hrs. Bacillus subtilis had the lowest protein concentration (3.034mg/ml) at 12hrs. Conclusion: This study showed that these rhizosphere microorganisms when applied as inoculants into the soil at different concentration of glyphosate can help increase the availability of soluble phosphates.