The forms of inorganic phosphorus extracted from soils by N sulphuric acid

摘要

Abstract Values for the amount of inorganic phosphorus extracted by N H2SO4 (Pa) from a range of New Zealand soils were compared with certain forms of inorganic phosphorus, determined by a fractionation procedure. Pa exceeded acid-extractable Ca-P for all samples. The Pa fraction was composed of acid-extractable Ca-P plus a part of secondary inorganic phosphorus. For weakly weathered soils, Pa exceeded the sum of acid-extractable Ca-P and non-occluded P, whereas in strongly weathered soils, in which acid-extractable Ca-P was absent, non-occluded P exceeded Pa. The decline in Ps with increasing degree of soil development was attributed to loss by leaching, conversion into organic phosphorus, and conversion into occluded forms of inorganic phosphorus.