干旱区生态环境知识资源中心

The aim of the present study was to evaluate the status of inorganic phosphorus (P) fractions in ten virgin soil profiles, and to study the relationships between P fractions and soil properties from Kohgyloyeh and Boir Ahmad province, Iran. The soils belonged to Alfisols, Entisols, Mollisols, and Inceptisols. Mean annual precipitation and temperature ranges were 450-850 mm and 12.2-22.4 degrees C, respectively. Inorganic P was fractionated by sequential extraction with NaHCO3, NH4OAc, MgCl2, NH4F, NaOH, citrate-dithionite-bicarbonate (CBD), and H2SO4, which are referred to as NaHCO3-P, NH4OAc-P, MgCl2-P, NH4F-P, NaOH-P, CBD-P, and H2SO4-P, respectively. Generally, the NaHCO3-P, NH4OAc-P, MgCl2-P, and NH4F-P were higher in surface horizons, especially wherever there was higher annual precipitation. Results showed that H2SO4-P constituted the largest inorganic P fractions in all profiles. For all the soils studied the distribution of P fractions was similar to that of weakly weathered soils under arid and semi-arid regions which represent an early stage of development. Pedogenic P compounds were higher where weathering was higher, i.e., in surface horizons and at higher annual precipitation.