Abstract:
The Increased Use Of The Herbicide, Glyphosate, To Control Weed Has Raised Concern Over Its Effect On Non Target Organisms In The Soil. This Research Focused On The Effect Of Glyphosate On Microbial Population And Enzyme Activity In The Soil. The Effect Of Glyphosate On Bacterial And Fungal Population And Urease And Phosphatase Activity Were Investigated By Treating Soil Sample At Five Concentrations Of 1%, 5%, 10%, 15%, 20% (V/W). Bacterial And Fungal Populations And Enzyme Activity Were Monitored At 7 Days Interval. Bacterial And Fungal Populations Was Enumerated By Spread Plate Method While Urease And Phosphatase Activity Was Analysed Using Spectrophotometer At 420 Nm And 405 Nm Respectively. The Highest Average Bacterial Count Of 1.31×109 Cfu/G Of Soil Was Obtained At 10% Treatment On Day 28 While The Lowest Average Bacteria Count Of 3.0×108 Cfu/G Of Soil Was Obtained At 20% Treatment On Day 35 Against The Control With 9.8×108 Cfu/G Of Soil And 8.1×108 Cfu/G Of Soil On Both Days, Respectively. The Lowest Average Fungal Count Of 3.3×107 Cfu/G Of Soil Was Obtained At 20% Treatment On Day 21 While The Highest Average Fungal Count Of 1.20×108 Cfu/G Of Soil Was Obtained At 10% Treatment On Day 28 Against Control With 6.5×107 Cfu/G Of Soil And 7.0×107cfu/G Of Soil On Both Days, Respectively. The Lowest Level Of Urease Activity Of 3.11±0.08 µG/G/H Was Observed On Day 35 In The Control While The Highest Level Of Urease Activity Of 22.55±2.60 µG/G/H Was Observed At 20% Glyphosate Treatment On Day 28.The Highest Level Of Phosphatase Activity Of 2.01±0.21 µG/G/H Was Observed At 10% Concentration On Day 0 While The Lowest Phosphatase Activity Of 0.73±0.11 µG/G/H. Was Observed On Day 35 In 20% Concentration. Preliminary Identification Of The Bacterial Isolates Showed Them As Belonging To Staphlococcu, Micrococcus, Escherichia Coli, Bacillus, Listeria, Streptococcus, Corynebacterium And Pseudomonas Species. The Fungal Isolates Were Identified As Belonging To Aspergillus, Trichophyton, Microsporium, Penicillum, Rhizopus, Fusarium, Cladosporium, Mucor, Rhodotorula, Candida And Cryptococcus Species. The Species Richness In The Soil Was Affected As Observed In The Decline Of Bacterial Species To Only Pseudomonas, Bacillus And Listeria Species And Fungi To Aspergillus, Microsporium, Rhizopus And Cryptococcus Species On Day 35 Of Incubation At 20% Concentration. Results Obtained From This Study Shows That Glyphosate Has Significant Effect At On The Microbial Population And Enzyme Activity In The Soil Based On The Dosage Applied
