PHOSPHORUS TRANSFORMATIONS IN CHRONOSEQUENCE OF SOILS DEVELOPED ON WIND-BLOWN SAND IN NEW ZEALAND .2. INORGANIC PHOSPHORUS

The rate of transformation of inorganic phosphorus fractions and forms was investigated in a chronosequence of weakly weathered soils developed on windblown sand. The net decline of acid‐extractable Ca‐P during 104 years of soil development was approximately 2600 kg/ha m profile. This fraction was progressively removed from surface horizons and had virtually disappeared from the oldest soil. Residual inorganic P, considered to be included apatite which is not extracted by 0·5 and 1N HC1, was relatively constant in profiles of the chronosequence but decreased in the oldest soil. In the younger soils, the NH4F‐P fraction was low but, with increasing time, the weight of this fraction increased, initially in surface horizons. The net accumulation of non‐occluded secondary inorganic P during 104 years was 360 kg/ha m profile and this was largely due to an increase in the NH4F‐P, rather than the 1st NaOH‐P fraction. There was no net shift from non‐occluded to occluded secondary inorganic P. Although apatite is initially present as inclusions within primary minerals in the wind‐blown sand, an extensive loss of P has occurred during 104 years. Copyright © 1969, Wiley Blackwell. All rights reserved