Isolation and Identification of Three Potassium-Solubilizing Bacteria from Rape Rhizospheric Soil and Their Effects on Ryegrass

Abstract

ABSTRACTMore than 90% of potassium (K) in soil exists in forms of insoluble silicate minerals and cannot be directly utilized by plants. K-solubilizing bacteria (KSB) can improve soil fertility and plant growth as biofertilizers by decomposing silicate minerals and releasing insoluble K into soluble forms. The objectives of this study were to isolate and characterize KSB from rape rhizospheric soil and to evaluate their effects on ryegrass growth. In this study, 16 cultivable potential KSB were isolated from rape rhizosphere at first. Then, quantitative analysis revealed that three KSB strains, named S-15, S-17 and S-18, showed the best K mineral solubilizing ability and they were identified as Mesorhizobium sp., Paenibacillus sp. and Arthrobacter sp. Inoculating the three strains into available K limit soil increased available K content significantly. The result of the pot experiment revealed that the three strains increased ryegrass growth vigor, biomass yield and K uptake to different degrees in available K deficient soil. S-17 showed the most pronounced ryegrass growth promotion ability. Further studies are required to determine the effects of the three KSB on mobilization of K-bearing minerals under field conditions.