Soil phosphorus fractions with different reclamation periods in the Tibet Autonomous Region, China

Soils with different reclamation period were collected from Jiangzi Counties of Shigatse region and Qiongjie Counties of Shannan region in the Tibet Autonomous Region, China. Soil phosphorus forms with different reclamation periods and rangeland were analyzed by the method of Hedley revised by Tiessen. The results of this study showed that the inorganic phosphorus fractions ranked in the following order: Dil.HClPi＞Conc.HClPi＞NaOHPi＞NaHCO3Pi＞H2OPi. Inorganic phosphorus fractions increased with the land reclamation years, in which Dil.HClPi and Conc.HCl`Pi had maximum increase. The rangeland with a small inorganic phosphorus pool in the Qiongjie County had a bigger organic phosphorus bank than when compared to the farmland. Organic phosphorus fractionation decreased when reclamation period was below 50 years, whereas increased when reclamation period was over 50 years.