Plant Nutrient Acquisition

pp 299-318

Phosphate-Solubilizing Microorganisms and Their Use

  • Mary Leggett
  • , Sanford Gleddie
  • , Greg Holloway

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The importance of phosphate (P) in plant nutrition cannot be underestimated. Its role in energy transfer is critical to plant reproduction and productivity. Many soil microorganisms make P more available to plants by solubilizing otherwise inaccessible forms of bound P. Although hundreds of P solubilizers have been studied, only two have been developed into commercial phosphate inoculants: Bacillus megatherium var. phosphaticum (Phosphobacterin) and Penicillium bilaii (Provide).

The lack of available phosphate inoculants is a result of the many biological, agronomic, commercial, and marketplace criteria a P solubilizer must meet to become commercially successful. The biological reality is that the organism, plant, and environment all interact to produce an effect on plant growth and yield. The P solubilizer must effectively colonize the rhizosphere and function in a broad range of environments. The agronomic reality is that the P solubilizer must perform under the full range of conditions seen by the farmer and must demonstrate a contribution to increased yield. This requires multi-year, multi-site field trials, an evaluation of the types of P solubilized, and a study of the range of crops for which an organism is effective. The commercial reality is that the P solubilizer must be amenable to a cost-effective production process, genetically stable, viable in formulation, and efficacious at a reasonable application rate and cost. The marketplace reality is that the organisms must be compatible with current farming practices (e.g. other inoculants and chemicals) and of proven economic benefit to the farmer. A well planned research program addressing all these areas is necessary to develop a commercial phosphate inoculant.

Key words

Commercial Inoculant Penicillium Phosphate Plant growth promotion Rhizobium Solubilizer