Cyclic salt as a dominant factor in the genesis of soils in South-Eastern Australia.

Abstract

A theory is presented suggesting that during the Recent Arid Period the rainfall was approximately half that of the present day and enabled cyclic salt to be accumulated in areas in south-eastern Australia, where it does not 'accumulate at present. The salinization and subsequent desalinization during the wetter conditions since the Arid Period have operated with varying degrees of intensity to produce solods, solodic and solonized soils over large areas. However, irrespective of the degree of intensity, some of the pre-Arid soils because of their chemical or physical properties have been able to resist these processes and remain unaffected. Five "pedogenetic zones" have been defined according to the degrees of intensity with which the salinization and desalinization processes are thought to have operated, and it is found that soil distribution and morphology is correlated with these defined zones. The zone in which the effect has been most intense has an average annual rainfall at present of between 20 and 30 in., and the most widespread soils, those formerly called red and yellow podzolics, are solodic soils and solods. The theory provides a reasonable explanation for the anoxalous distribution of soils within the "podzol" zone where those showing the greatest degree of horizon differentiation (solods and solodic soils) occur in the driest parts. In addition, the postulated processes for the formation of the soils provide a reason why molybdenum deficiency is so common on these soils in zone 3.