Changes of inorganic fractions of phosphorus with equilibration time in flooded and moist soils

Abstract

Part of a thesis presented in partial fulfillment of the requirements for the Ph. D. degree, Ohio State University, Columbus, Ohio. Former International Rice Research Institute Fellow, Dr. Espada is professor of soil chemistry at the College of Agriculture, Central Philippine University, Iloilo City, Philippines.

The application of phosphate fertilizers to the soil seldom results in the recovery of more than 10 to 20 percent of the phosphorus. Fixation occurs simultaneously with the dissolution of phosphate from the fertilizer especially when the soil environment contains ions such as Fe-|-3, Al-|-3, Ca-|-2, K-|-, NH4-|-, and others. Several discrete mineral species or phosphate compounds were identified in solution supporting both phosphate ions and one or more of these ions [12, 13, 14]. The major portion of inorganic phosphorus in the soil is bound by calcium, aluminum, and iron; the relative abundance of each being controlled by soil reaction.