Phosphate solubilizing microorganisms isolated from manoa soil in Oahu, Hawai’i

Abstract

Phosphorus (P) is an important nutrient next to nitrogen. It is an essential element in the soil for plant development and growth of microorganisms. The common method to supply phosphate to plants is to add soluble mineral phosphate fertilizers into soil. However, this practice is not cost effective. This study attempted to isolate phosphate-solubilizing microorganisms which can solubilize insoluble rock phosphate to a soluble form. Soil microorganisms were isolated from root and soil samples at the rocky site of Waahila Ridge, Manoa area. Large numbers of fungi and bacteria were recovered. The microorganisms were purified by transferring twenty-four of single colonies to YMA agar. The isolates were then examined for their ability in rock phosphate solubilization. All isolates showed the positive activity and generated different levels of soluble phosphate concentration associated pH drop in the liquid medium. Two out of nineteen isolates showed the highest activity in solubilizing North Carolina rock phosphate and the soluble phosphate concentration in the liquid medium were 19.33mg/L and 18.1mg/L. This study demonstrated that selected soil microorganisms could convert insoluble phosphate to soluble form generally through the process of acidification.