Phosphorous availability is dependent on soil physical properties (organic matter, clay content, moisture, aeration, etc.) and chemical properties (pH, texture, etc.). The total soil phosphorous exists in two forms: organic and inorganic. Organic phosphorus is the product of the decomposition of plants, animals, and microbes; while it is not available to the plants, it will be digested by soil microbes converting a portion of the phosphorus to plant available in the form of orthophosphate. The inorganic phosphorous can be in two forms, one in soil solution, which is available to the plant and often represents a small proportion of the soil phosphorous. In addition, we can find the inorganic phosphorous as insoluble or bound phosphorus (Pi), such as calcium phosphate in alkaline soils and aluminum and iron phosphates in acidic soils. The chemical conversion of Pi or bound P to soluble, plant-available P in the soil is generally considered pH dependent, driven by the production of low molecular weight organic acids by plants and beneficial soil microbes. Depending on the soil pH, orthophosphate ions (H2PO4–, HPO42-) are the forms of phosphorus most accessible to plants. In acidic soils with high levels of metal ions like Al3+ and Fe3+, phosphate is bound-up in the form of the corresponding insoluble metal phosphates, e.g., AlPO4 and FePO4. In these situations, displacement of inorganic phosphate (Pi) from Fe and Al ions occurs through “ligand exchange”, meaning the organic acids compete with Pi for Al and Fe binding sites, driving the release of plant-available phosphorous into the soil. The BiOWiSH® Crop products support this system in two ways.
First, BiOWiSH® Bacillus beneficial microbes associate with the roots of their host plant, augmenting the plant’s hologenome and supporting the expression of natural plant processes. Through these processes, the plant recruits beneficial soil native microbes from the root’s surrounding soil, including those which drive the release of plant-available phosphate from the soil. Second, BiOWiSH® Crop products optimize soil conditions for greater root mass and stimulates the release of root exudates, which include organic acids that help shift the equilibrium of bound phosphate towards more soluble phosphate.
Therefore, the addition of BiOWiSH® Crop products improves phosphorus mobilization and availability by promoting the growth of soil microbes capable of chemically reducing metal phosphates, enhancing the uptake of the released phosphate by plants and shifting the equilibrium between bound and soluble phosphate toward more soluble phosphate where the optimized soil conditions have contributed to greater root mass, allowing for additional nutrients to be captured.