Which form of phosphorus is abundant but not available for plant uptake?

Organic phosphorus is a significant component of the phosphorus cycle in ecosystems. It exists in forms that are part of organic matter, such as plant and animal residues, living organisms, and microbial biomass. While this form of phosphorus is abundant in soils, it is not readily available for plant uptake because plants can only absorb phosphorus in inorganic forms, typically as phosphate ions (H2PO4^- or HPO4^2-).

The organic phosphorus must first be mineralized by soil microorganisms into inorganic compounds before it can be utilized by plants. This process makes organic phosphorus an important reservoir of nutrients, but its availability is limited until it is converted into forms that plants can absorb. Understanding this dynamic is crucial for effective nutrient management and ensuring that plants receive adequate phosphorus for their growth and development.