Abstract: Transformaion of applied phosphorus and yield response of naked oat to P fertilizer were studied in chestnut soil, using fractionation scheme of inorganic P in calcareous soils. The results obtained showed that applied P was transformated into Ca2-P, Ca8-P, Al-P, Fe-P after fertilization during incubation for short time. The content of Ca2-P was decreased repidly in the following days but that of Ca8-P, Al-P, Fe-P were increased. 31. 1% of applied P was absorbed by naked oat and 68.9% was resided in the soil when P fertilizer was applied in the soil with naked oats. In the residual P Ca2-P accounted for 28.9% of total applied P, Ca8-P 11.0%. Al-P 10.3%, Fe-P 5.5%, O-P 9.5% and Ca10-P 3.7%. The coated P decreased the transformation of Ca2 - P to Ca8-P increased transformation rate of applied P into Al-P but transformation into Fe-P, O-P were decreased. P use efficiency was incredsed by 2.9 percentage point as compared with uncoated P. P fertilizer increased yield of naked oat by 178% in the soil with low levels of available phosphorus.