Native couch grasses for revegetating severely salinised sites on the inland slopes of NSW

Abstract

Two scalded saline sites on the inland slopes of NSW were selected for an evaluation of ten accessions of warm-season stoloniferous/rhizomatous grass species: common couch (Cynodon dactylon), marine couch (Sporobolus virginicus), rats-tail couch (S. mitchellii), salt-water couch (Paspalum vaginatum), water couch (P. distichum) and one exotic, kikuyu (Pennisetum clandestinum). Most species performed well at Wagga Wagga but only common couch, marine couch and salt-water couch did at Manildra, where they consistently outperformed the other native species in terms of survival, groundcover and vigour. Salt-water couch had the highest mean vegetative cover at both sites. Differences in salinity, pH (acid cf. alkaline) and particularly topsoil moisture probably accounted for differing plant performances at the two sites. In a follow-up production study of the most successful accessions under relatively dry conditions at Manildra, the 'Yamba' accession of marine couch consistently produced more leaf/seedhead dry matter (1057 ± 172 kg/ha) during the growing season than the others. However, salt-water couch consistently produced more ex-plot stolon/rhizome dry matter (974 ± 127 kg/ha) than the other two species. This probably explained its ability, unlike marine couch, to maintain groundcover during a regime of regular cutting. Further evaluation under grazing and recreational uses is recommended. The genetic material evaluated was only a small sample of salt-tolerant native grasses. The variable performance of the four accessions of rats-tail couch, for example, suggested that more salt-tolerant types are likely to be found.