Phosphorus content in the natural soils is generally quite low.
The majority of the prairie soils are considered marginal to deficient in the plant-available phosphorus content required for crop production. Thus, farmers routinely apply phosphorus-containing fertilizers and manure to their fields to meet crop requirements.
However, a significant fraction of the phosphorus applied to soils may convert to highly insoluble forms that are not available for plant uptake.
Soil phosphorus exists in three general chemical forms - organic phosphorus compounds, calcium-bound inorganic phosphorus compounds, and iron or aluminum bound inorganic phosphorus compounds.
Of the inorganic forms, calcium-bound phosphorus compounds are generally predominant in the alkaline soils, while iron and aluminum compounds are predominant in the acidic soils. These inorganic compounds and organic phosphorus bound to the soil organic matter contribute to phosphorus dissolved in soil solution in the form of phosphate ions that plant roots take up.
The symbiotic relationship between phosphate ions and mycorrhizal fungi assist the plant uptake.
The microscopic, thread-like hyphae of these fungi can extend into soils several centimeters from root surface and absorb phosphate ions from soil solution to translocate them to the roots. The amount of phosphorus available for plant uptake in the soil solution is very low, seldom exceeding 1/10,000 of the total phosphorus in soils.
We will look at the phenomenon controlling phosphorus solubility and mobilization in upcoming articles.
To read more about Mycorrhizal fungi, Get Associated With Mycorrhizae!