Microbial and Heavy Metals Qualities of Agricultural Soil of Tsafe Local Government Area in Zamfara State, Nigeria

This research was carried out for six months, during which soil samples of the council area were analyzed. 25 aerobic heterotrophic bacteria (AHB), 15 non-symbiotic nitrogen fixing bacteria (NFB) and 10 fungi were isolated from the soil. The mean total count of aerobic heterotrophic bacteria (AHB) are 5.8x106 cfu/g, 5.8.3x106 cfu/g, 7.3x106 cfu/g, 7.4x106 cfu/g and 5.6x106 cfu/g of soil for Zone 1 (ZN1), Zone 2 (ZN2), Zone 3 (ZN3), Zone 4 (ZN4), and Zone 5 (ZN5). Similarly, the mean total count of non-symbiotic nitrogen fixing bacteria (NFB) in the soil were 5.1x106cfu/g, 4.0x106cfu/g, 5.7x106cfu/g, 5.6x106cfu/g and 4.5x106 cfu/g of soil for ZN1, ZN2, ZN3, ZN4, and ZN5 respectively. The mean total fungal count (TFC) recorded were 7.9x102cfu/g, 16.6x102cfu/g, 9.3x102cfu/g, 7.2x102cfu/g and 14.3x102cfu/g of soil for ZN1, ZN2, ZN3, ZN4 and ZN5 respectively. Bacillus, Pseudomonas, Staphylococcus, Micrococcus, Klebsiella, Escherichia were the predominant bacteria recorded. Fungal specie isolated in the soil are; Aspergillus, Rhizopus, Mucor, Penicillium and Fusarium. Lead concentration in the soil was highest (11.3±2.5mg/kg), followed by Iron (10.9±2.05), Zinc (9.42±1.75mg/kg), Chromium (7.86±2.6mg/kg), Copper(7.28±1.76mg/kg), Nickel (7.24±1.98mg/kg), and Cadmium was lowest (6.88±1.2mg/kg). Chromium (17.8±2.0), Iron (12.5±0.5), Lead (16.5±1.3), Nickel (15.0±4.0), and Iron (14.8±1.1) were the dominant heavy metals in ZN 1, ZN 2, ZN 3, ZN 4, and ZN 5 respectively. Correlation results between the microbial counts and heavy metal concentrations revealed no general pattern of relationship between the variables in the soil. Key Words: Aerobic heterotrophic bacteria; agricultural soil; heavy metals; microbial; nitrogen fixing bacteria.