Soil–Plant Relationships in Saline Wastelands: Vegetation, Soils, and Successional Changes, During Biological Amelioration

An ecological survey of undisturbed saline wastelands and adjacent fields of Kallar Grass (Leptochloa fusca) was undertaken to study species distribution in relation to soil conditions and changes in species composition during amelioration processes. Five plant communities, represented by Atriplex crassifolia C.A. Mey., Cynodon dactylon (L.) Pers., Desmostachya bipinnata (L.) Stapf, Suaeda fruticosa (L.) Forssk., and Eleusine flagellifera Nees, had colonized undisturbed areas. Soils of plant communities dominated by these species showed significant variations in salinity and sodicity. S. fruticosa was dominant on highly saline–sodic soil, Cynodon on slightly saline and moderately sodic soil, whereas D. bipinnata showed little variation in cover percentage with changes in salinity and sodicity of soil. These three species had wide ecological amplitude compared with E. flagellifera and A. crassifolia, which were restricted to non-saline and marginally saline–sodic soils, respectively.

Sodicity and soil structure

Sodic soils are widespread in Australia reflecting the predominance of sodium chloride in groundwaters and soil solutions. Sodic soils are subject to severe structural degradation and restrict plant performance through poor soil-water and soil-air relations. Sodicity is shown to be a latent problem in saline-sodic soils where deleterious effects are evident only after leaching profiles free of salts. A classification of sodic soils based on sodium adsorption ratio, pH and electrolyte conductivity is outlined. Current understanding of the processes and the component mechanisms of sodic soil behaviour are integrated to form the necessary bases for practical solutions in the long term and to define areas for research. The principles of organic and biological amelioration of sodicity, as alternatives to costly inorganic amendments, are discussed.