Phosphorus sorption in tropical soils

Phosphorus is an important primary nutrient required by plants in large quantities. The various forms of P that plants can take up are the primary monobasic phosphate ion (H2PO4-), secondary dibasic phosphate ion (HPO42-) and phosphate ion (PO43-). In tropical soils, phosphorus adsorption is a major process that controls its availability to crops. Soils with low phosphorus adsorption capacity are often unable to supply adequate phosphorus to the growing crops thereby affecting their yields. This paper reviews the phosphorus adsorption phenomenon in a tropical soil. The review showed that Langmuir isotherm, Freundlich isotherm, Brunauer-Emmett-Teller (BET) isotherm, Dubinin-Radushkevich, and Temkin isotherm are the mostly used isotherms models for describing phosphorus adsorption. From the review, soil acidity and alkalinity, soil temperature and the electrical potential of clay surface are the main factors influencing phosphorus adsorption. Also, precipitation was discovered to be the main mechanism of P adsorption in tropical soils. Fertilization practices such as the addition of organic manure, crop residues, rock phosphate, water-soluble P fertilizers and incorporation of phosphorus solubilizing organism are highly recommended to increase P solubility and availability in highly weathered soil.