Use of Sodium Edta in the Determination of Soil Organic Phosphorus

Summary The organic phosphorus contents of a range of soils were determined by the extraction method of Mehta et al. (1954) and by the ignition method of Legg and Black (1955) and the results compared with those obtained by an extraction method using Na 2 EDTA and caustic soda. The two extraction methods compared well, especially on soils over pH 5. Lower values were obtained by the ignition method on the more acid soils. The Na 2 EDTA method caused less hydrolysis of added glucose‐I‐phosphate than did either of the other methods. In combination with caustic soda Na, EDTA was less effective than Na 2 EDTA.