In order to evaluate the phosphorus status of upland soils in Myanmar, 26 upland and 8 lowland soil samples were collected form surface (0～15cm deep) and subsurface (15～30cm deep) layers at 17 different places on different parent materials in eastern, central and lower parts of Myanmar. Concentrations of total, available, organic, and inorganic P were considerably varied with soils with ranges of 132 to 1414, 1 to 135, 37 to 265, and 89 to1167mg P/kg, respectively. The concentrations were higher for the soils applied with P fertilizer in all of the four P parameters. In most soils, the available, organic and inorganic P concentrations depended on the concentration of total P. In the sequential fractionation, inorganic P was separated into soluble and loosely-bound P, Al-P, Fe-P, occluded P, and Ca-P in the slightly acid to neutral soils and into Ca_2-P, Ca_8-P, Al-P, Fe-P, occluded P, and Ca10-P in the neutral to slightly alkaline soils. In the former soils, the available P concentration was correlated with the concentrations of soluble and loosely-bound P, Al-P and Ca-P at the 1% significant level, and those pools were estimated as the main source for available P. In the latter soils, although Ca2-P, Ca8-P and Al-P were the predominant forms, the total P concentration was highly correlated with the concentrations of all forms of inorganic P, and total P was consequently considered to contribute to increase of plant-available P. Suitable crop selection or appropriate soil and fertilizer management practice was suggested depending on the phosphorus status of soils.
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