REVEGETATION OF A SCALDED SALINE DISCHARGE ZONE IN CENTRAL QUEENSLAND.1. SELECTION OF TREE SPECIES AND EVALUATION OF AN ESTABLISHMENT TECHNIQUE

Species selection trials using 38 tree species were undertaken on sali nised, waterlogged land [watertable within about 1 m of soil surface, electrical conductivity (EC(w)) about 30 dS/m, surface soil (0-0.1 m) EC(1:5) about 10 dS/m] in coastal central Queensland. Casuarina glauca and C. obesa gave best survival and growth, while Eucalyptus camaldul ensis and C. cunninghamiana gave good initial survival but succumbed t o salt and waterlogging stress after several years. The role of soil m ounding and mulching for the establishment of C. glauca was investigat ed in a factorial experiment involving 2 levels of soil mounding (nil, 0.15 m) and 4 mulch conditions (nil, hay, black plastic, white plasti c), and in a second experiment involving bagasse, soil amendment with calcium, and the installation of a double ridge in the mound. The low soil mounding had little effect on plant survival or growth, or soil c onductivity; however, mulching greatly influenced these parameters (e. g. about 2 years after a summer planting, tree survival, tree growth, and surface soil conductivity in a plastic mulch treatment was 566, 21 0, and 60%, respectively, of values of the no-mulch treatment, with a mean tree height of about 3 m in the plastic mulch treatment). Plastic mulch was recommended over hay or bagasse mulch for short-term (<2 ye ars) increase in plant survival and growth (e.g. 15 months after a sum mer planting, height of plants established in plastic mulch rows was 1 24% of that in hay-mulched rows). The incorporation of a small trough in the crown of the bed was found to improve plant growth significantl y (tree height in troughed mounds 120% of that in untroughed mounds, 1 5 months after planting), but did not improve establishment. Soil amel ioration with lime, gypsum, or dolomite at 3.0 t/ha did not improve pl ant growth. A further trial at another salinised site confirmed the su ccess of the plastic mulch-crown trough technique, relative to convent ional preparation techniques (i.e. ripping).