Establishment of trees and shrubs on a saline site using drip irrigation

Summary

A field trial has been established near Kerang, in north-central Victoria, to provide information on methods and effects of growing trees on salt-affected land. The experimental site comprised a saline sodic clay soil overlying highly saline groundwater within two metres of the surface. Measures taken to enable tree establishment included ploughing, gypsum incorporation, drip irrigation and sub-surface drainage. High mortality of planted seedlings occurred in the first and second years after planting as a result of salinity, frost and other site factors. Eucalyptus camaldulensis (river red gum) was the most successful of 22 species planted in terms of both survival and height growth. E. astringens (brown mallet), E. brockwayi (Dundas mahogany), E. largiflorens (black box), E. leucoxylon (yellow gum), E. occidentals (swamp yate), Leptospermum lanigerum (woolly tea-tree) and Melaleuca lanceolata (moonah) also grew satisfactorily.

Analysis of soil samples collected at intervals during the study showed a substantial improvement in site conditions in the first two years after planting, including decreasing salinity of the surface soil and upper profile, and an increase in exchangeable calcium content to 25 cm depth. These effects were attributed to the site treatments rather than the trees, although the trees might exert an ameliorative effect on the soil and groundwater in future years. The establishment methods used in the trial are applicable to tree establishment on similar sites in the irrigation areas of northern Victoria.