Phosphorus is an important plant nutrient which is in short supply in soils for plant growth because much of the soluble phosphate applied to soil as fertilizer is fixed and only 10-18 % is utilized by the current crop. Plant availability of inorganic phosphorus can be limited by formation of sparingly soluble calcium phosphate, particularly in alkaline and calcareous soil; by adsorption to Fe- and Al- oxide surface in acid soils and by formation of Fe \ Al- P complexes with humic acids. Plant roots acquire phosphorus as inorganic phosphorus from the soil solution.