Soil studies using sweet vernal to assess element availability IV. Phosphorus

Abstract

Summary The phosphorus status of New Zealand topsoils is surveyed in terms of total, organic, and inorganic phosphorus fractions, solubility of the inorganic phosphorus in N H2SO4 and phosphorus content of the grass, sweet vernal (Anthoxanthum odoratum). Use is made of the genetic soil classification to show how the plant and soil phosphorus values are influenced by the nature and degree of the soil-forming processes. The total phosphorus contents of mineral topsoils at early stages of weathering reflect the nature of the parent rock in that red-brown loams from basalt and yellow-brown loams from andesite contain larger amounts of phosphorus than soils from more acidic rocks such as yellow-brown pumice soils and the zonal soils. Soil development sequences, representing increasing degrees of weathering and leaching, from groups of parent rocks, show a decrease in the phosphorus content of the topsoils. The greater the iron and aluminium content of the parent rock, the greater is the proportion of the origi...