Phosphorous (P) is an essential element to living organisms and is found in proteins & enzymes, nucleic acid, cell membranes and in the cellular energy producing pathways. It is found as an inorganic (soluble and insoluble) form, perhaps bound to clay minerals or bound in organic complexes. At around  400-1200 mg kg^-1 soil phosphorous is relatively abundant  but only 5% may be available (Campbell, 1983). Application of insoluble P as a fertiliser is preferable to soluble P due to its slow conversion to soluble P and retention time in the soil (Ehrlich, 1996). Soluble P being more readily removed from the soil.

In the phosphorous cycle, the main inputs are from industrial sources, rock minerals (dissolved by organic acids produced from microorganisms) and fertilisers. The addition of too much fertiliser on land may result in eutrophication of lakes from run off and algal growth. The decay of organic matter releases phosphorous contained in skeletons, nucleic acids and lipids.

Phosphorous is generally unavailable to plants until solubilised by microorganisms (Ehrlich, 1996). Both fungi and bacteria can solubilise organic P into inorganic P to a form readily available to the plant. The uptake of phosphorous to plants can be increased if the plants become associated with a mycorrhizal fungus. Here, there is an intimate close proximity of the fungi to the plant root system with the fungal hyphae effectively increases the root volume available for phosphorous uptake.

Back to The Biotransformation of elements

Back to The function of the soil community