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Effects five low molecular weight organic acids and their selective combinations on the mobilization of phosphorous on two slightly and moderately soils from Ethiopia have been investigated. To evaluate the effects of five LMWOAs and their combinations the soils were thermostatically incubated at 25°C and 40% moisture content for 4 days with LMWOAs by keeping the concentration of LMWOAs at 3.33 mmol Kg-1. Soil pH and Olsen P were analyzed after incubation. All the organic acids used in this study as well as their combinations increased the amounts of NaHCO3- P differently in the order of citric+oxalic citric citric+oxalic+tartaric tarataric oxalic oxalic+malic maleic citric+maleic malic acids (p0.05). These results suggest that organic acids altered the P fractions from stable, sparingly soluble forms to easily dissolvable forms, and that chelation or precipitation of cations with organic ligands occur before biodegradation of these ligands. Adding the LMWOAs treatment to the soils can provide an environmentally compatible alternative that may have a vital use in the P deficient environments.
