The Changes of Phosphate Fraction in Andisol and Oxisol by Organic Matter Application

Abstract

Soil phosphate (P) exists in various chemical forms, including inorganic P (Pi) and organic P (Po), which differ widely in their behavior and fate in soils. Some fractions of soil P are insoluble forms and each concentration depends on soil types. The problem of P deficiency in Andisol and Oxisol can potentially be solved by the progressive return of organic materials to soil. However, the quantity, quality, and management of this practice are fundamental factors that affect the availability of P from residues. The objectives of this research are to evaluate: (1) the changes of fractions of soil P in Andisol and Oxisol by adding organic acid and organic matter, and (2) enhancement of available soil P in Andisol and Oxisol. Four treatments have been done i.e: (1) control, (2) citric acid, (3) oxalic acid, and (4) soybean biomass. Soil was incubated for 30 days. The results show that application of soybean biomass increases the total P and the availability of P in both soil types. Furthermore, model of changes of soil P fractionation are different between Andisol and Oxisol. In addition, 30 days incubation does not influence the decreased of P retension in Andisol; it shows that adsorption site of Andisol is higher than Oxisol.