Soil Chemistry in Relation to the New Zealand Genetic Soil Classification

The New Zealand genetic soil classification was developed to reflect the impress of the local soil-forming factors on predominantly young geological materials. Marked climatically controlled zonality is evident on “normal” sites, on “normal” (acid-intermediate) parent materials, while intrazonal character is exhibited by soils derived from “unusual” parent materials (volcanic rocks, limestone, etc.), and azonal character by soils on unstable sites. Soil parent material and degree of soil development are reflected in the clay mineralogy and the soil chemistry. In particular, topsoil and subsoil values for the stable chemical parameters phosphate retention, adsorbed sulphate, long-term potassium supplying power (Kc), and reserve magnesium (Mgr), all show marked differences among genetic groups or subgroups.