A Quick Method to Extract Organic Phosphorus from Soils

The objective of this study was to develop a quick method for extracting organic P from soils. Organic P was extracted from soils by a proposed quick method (0.3 M NaOH sonified for 3 min) and compared with other methods: (i) sequential extraction with 0.3 M NaOH, concentrated HC1, and 0.5 M NaOH (modified Mehta method), and (ii) extraction of ignited (540°C) and nonignited samples with 0.5 M H 2 SO 4 (Saunders and Williams method). The study used four soils with different mineralogies belonging to the following great groups: Hydrandepts, Fluvaquents, Haplustolls, and Gibbsiorthoxs. The proposed quick method extracted, on the average, 89% as much organic P as the modified Mehta method from the soils studied. In six out of ten samples the Saunders‐Williams method yielded more organic P than the other two methods, probably due to an increase in solubility of Fe and Al phosphate minerals after heating. It is concluded that the proposed quick method can be used to extract organic P from soils. It gives results comparable to the more tedious method of Mehta and is probably more accurate than the Saunders and Williams method for highly weathered soils.