What is the soil chemical property affect to phosphorus availability in soils? What is the most importance factor?
Thanks for your answer, Anil Kumar Singh. How do you think about the effect of Redox condition to phosphorus availability?
P availability in soils varies with many factors. Listed below are some important soil factors affecting P availability in soils:
Amount of clay: Soils high in clay content will fix more P than those containing less clay.
Type of clay: Soils high in certain types of clay minerals like kaolinite, Al, Fe oxides and hydroxides (common in the regions of high rainfall and temperatures), and amorphous clay minerals like allophone, imogolite and humus-Al complexes (common in soils formed in volcanic ash) retain or fix more added P than other soils .Regardless of clay type, fertilizer P is converted to less available forms.
Soil pH: In soil dominated by 2:1 type clays, solubility of various P compounds are largely determined by pH. Phosphates of Fe, Mn and Al have low solubility. They dominate in acid soil. Insoluble Ca and Mg compounds exist above pH 7.0. The most soluble or available P forms exist in the 6.0 to 7.0 range. The mechanisms of P fixation in highly weathered soils of the tropics (Ultisol and Oxisols dominated by Al and Fe oxides and kaolinite) and in soils derived from organic ash (Andisols) are different. This process retain appreciable amount of applied P in the pH range from 5 to 7.0. Lime application on tropical soils corrects Al toxicity and Ca deficiency, and the correction of these factors leads to an increase in P uptake even though liming has very little direct effect on P fixation.
Both soil pH and nature of clay might be the most important factors of P availability.
Hope you find this input useful.
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