Prospects for using soil microorganisms to improve the acquisition of phosphorus by plants

Microorganisms play an important role in the acquisition and transfer of nutrients in soil. For phosphorus (P), soil microorganisms are involved in a range of processes that affect P transformation and thus influence the subsequent availability of P (as phosphate) to plant roots. In particular, microorganisms can solubilize and mineralize P from inorganic and organic pools of total soil P. In addition, microorganisms may effectively increase the surface area of roots. Also, the microbial biomass itself contains a large pool of immobilized P that potentially is available to plants. Given that most soils are deficient in plant-available P and that P fertilizer represents a significant cost for agricultural production throughout the world, there is interest in using soil microorganisms as inoculants to mobilize P from poorly available sources in soil. Although potential clearly exists for developing such inoculants, their widespread application remains limited by a poor understanding of microbial ecology and population dynamics in soil, and by inconsistent performance over a range of environments. Furthermore, promotion of growth of plants in soil, as a consequence of microbial inoculation, may not necessarily be associated with characteristics such as P solubilization, which are manifest under laboratory conditions.