Soil Microbial Activities in Soybean Rhizosphere Inoculated with Bradyrhizobium and Mycorrhizal Fungi

This study was carried out to investigate the activities of soil microorganisms in the soybean rhizosphere inoculated with bradyrhizobium and mycorrhizal fungi. It involves a field experiment carried out at Federal University of Agricultural, Abeokuta, Nigeria, using Randomized Complete Block Design (RCBD). Treatments applied included 4.5 kg/ha poultry manure, 40 kg/ha Single Superphosphate, Mycorrhizal and 200 kg/ha of soybean seed and 1 g/ha Bradyrhizobium. Treatments were replicated thrice. Result showed significant difference between treatments on yield, growth and biomass activities in soybean production. Poultry manure, Phosphorus source, and Bradyrhizobium gave highest plant height of 47.99 and respectively at 14 WAP. Mycorrhizal with 10 tons poultry manure gave highest yield (0.12 t/ha). Microbial activities were significantly influenced by treatments with Bradyrhizobium inoculation in giving higher total bacteria count, total fungal count, microbial biomass C. Single Superphosphate in total bacterial count and microbial biomass N; poultry manure of 5 tons in total fungal count, microbial biomass C, N and P (p ≥ 0.05): Bradyrhizobium, and 5 tons of poultry manure gave highest total fungal count (0.07 CFU/g), 10 tons poultry manure gave the highest total bacterial count (1.26 CFU/g), and 5 tons poultry manure gave highest microbial biomass C (198.1 mg/kg), N (124.9 mg/kg) and P (232.2 mg/kg). Soil N (0.16%) and organic C (17.11%) were highest in plot treated with 5 tons poultry manure (0.16% for N and 17.11% for organic C), while Bradyrhizobium gave highest available P (14.16 mg/kg). Cellulase activities was highest in plots without Bradyrhizobium (0.14 mg/kg), mycorrhizal (0.14 mg/kg), 5 tons poultry manure (0.4 t/ha), 10 tons poultry manure (0.14 t/a), while protease and urease activities were highest in plots with 5 tons poultry manure (0.13 mg/kg for protease and 0.17 mg/kg for urease). Addition of 5 tons of poultry manure application increased soil microbial activities, growth and yield of soybean.