Phosphorus Fractions and Availability in an Albic Bleached Meadow Soil

The availability and mobility of P in soils is dependent on its chemical form. The objectives of this study were to investigate P fractions and availability in albic bleached luvisol meadow soils. Soil samples were collected from the albic bleached luvisol meadow soils (Albaqualfs) of the Sanjiang Plain in China and analyzed for total P (TP) as well as the forms and availability of P. The results showed that TP, inorganic P (Pinor), organic P (Por), and plant-available P (AP) averaged 865.1, 452.4, 412.6, and 46.6 mg kg(-1), respectively. In addition, soluble and loosely bound (S/L-P), Al-bound (Al-P), Fe-bound (Fe-P), reductant-soluble, and Ca-bound P (Ca-P) P, on average accounted for 0.3, 6.6, 27.9, 6.9, and 5.6%, respectively, of TP. The Pinor content was slightly higher than the Por content. Furthermore, approximately 53% of Pinor was composed of Fe-P. The AP was significantly correlated with Pinor or "active" P but not correlated with Por. In addition, AP was correlated with Al-P, Ca-P, Fe-P, and S/L-P, with a maximum correlation coefficient of 0.792 for AP vs. Al-P. Both the absolute content of AP and its proportion of TP were generally high in the albic bleached meadow soil of Sanjiang Plain. The P in the albic bleached luvisol meadow soil was mainly associated with Fe oxides and organic matter, and Fe-P supports the majority of available P.