Some improvements of the fractionation method of organic phosphorus in calcareous soils

Some improvements of the fractionation of organic phosphorus (P-0) in calcareous soils were made on the basis of different soil extractants. Labile P-0 contained in soil microorganisms was extracted by fumigation of soil with chloroform (CHCl3). The shaking time for extracting labile P-0, moderately labile P-0 and stable P-0 was shortened to 20 min, 2 h and 2 h, respectively, by using ultrasonic treatment. For extracting soil stable P-0 effectively, the concentration of NaOH was reexamined and 0.05 mol/l NaOH was proved to be suitable. According to the mineralization rate, stable P-0 can be subdivided into moderately stable P-0 and highly stable P-0 by adjusting the alkali solution to pH 3.00 as the suitable acidity. (C) 1999 Elsevier Science B.V. All rights reserved.