Table Of ContentsNext Page

Native couch grasses for saline site revegetation

W.S. Semple1, I.J. Cole2 and T.B. Koen2

1Department of Land and Water Conservation (DLWC), PO Box 53, Orange 2800
2
DLWC Centre for Natural Resources, PO Box 445, Cowra 2794

Abstract

Nine accessions of five species of mat-forming native perennial grass were evaluated on two saline scalds in inland NSW.

Survival of all accessions of three species, common couch grass (Cynodon dactylon), marine couch (Sporobolus virginicus) and saltwater couch (Paspalum vaginatum), was high at both sites. Survival of accessions of the other two species, condamine couch (Sporobolus mitchellii) and water couch (Paspalum distichum), was moderate at one site (Wagga) but low at the other (Manildra). Further evaluation of their performance under grazing (i.e. on farm) and recreational (e.g. playing field) uses is recommended.

A variety of other salt-tolerant native grasses have potential for revegetating saline sites but remain to be evaluated in the field.

Introduction

Re-establishing vegetation on saline scalds is unlikely to affect the causes of salinisation, though lowered water tables following the establishment of saltbushes has been reported (Barrett-Lennard and Malcolm 1995). The main benefits of revegetation appear to be in animal production, aesthetics, carbon sequestration, reduced erosion, habitat value, flood mitigation (e.g. Malcolm and Lloyd 2001) and in some urban areas, restoration of ground cover to salinised playing fields and lawns.

In some situations, the presence of salt-tolerant annuals such as sea barley (Hordeum marinum) and/or common weeds (e.g. Sonchus oleraceus), which are able to exploit seasonal reductions in salinity, may be preferable to no ground cover at all. More commonly, a productive pasture such as can be provided by well-managed stands of salt-tolerant exotics such as tall wheatgrass (Thinopyrum ponticum [T. elongatum]) and/or strawberry clover (Trifolium fragiferum) will be the aim of revegetation. However, as with all introduced pasture species, there is the possibility that they may escape from the site where they were planted and become weeds as has been reported for tall wheatgrass in Victoria.

For this reason alone, productive native species may be an attractive option. In saline areas managed for conservation, native species would be the preferred revegetation species.

A wide variety of native species occur on saline sites (e.g. see Matters and Bozon 1989, Semple 1996) and some, e.g. Diplachne fusca [Leptochloa fusca] (FitzGerald and Fogarty 1992), Sporobolus virginicus, S. mitchellii and Paspalum vaginatum (Truong and Roberts 1992), have shown promise in field evaluation trials.

The aim of the experiment described below was to evaluate the performance of some warm-season native grasses on saline scalds in inland NSW. Low-growing stoloniferous and/or rhizomatous (“mat-forming”) species were selected because of their potential use in a variety of situations including salinised urban areas.

All species evaluated were native (Harden 1993) though they also occur naturally outside Australia.

Methods

Accessions of vegetative material of five rhizomatous/stoloniferous native grass species were collected from nine sites in NSW in early 1999 (Table 1). All species were considered to have at least moderate forage value by Cunningham et al. (1981) or Truong and Roberts (1992). About 100 cuttings were taken from each and propagated in plastic tubes in the glasshouse at Cowra.

Two apparently uniform areas of bare saline seepage scald were selected as experimental sites; one near Wagga (mean pH = 5.2, ECe = 32.3 dSm-1) and the other near Manildra (pH = 9.2, ECe = 22.1 dSm-1). Sites were fenced ready for planting in early spring 1999.

The nine accessions were planted in separate 0.25 m2 plots on a three by three plot grid, using a randomised blocks design with eight contiguous replicates.

Four cuttings of each accession were planted in each plot, mulched with cereal straw at 3 t/ha and given a generous watering. Nitram was applied at 100 kg/ha in mid-spring 1999 and 2000. Small plots were used in an attempt to accommodate high variability over small distances at saline sites (Semple and Koen 1998).

At regular intervals during the growing season, plants were monitored for survival, vigour and groundcover until spring 2000 (Wagga) and autumn 2001 (Manildra). As data are still being analysed, only the preliminary survival data are considered in this paper.

Table 1. Native species evaluated on saline scalds near Manildra and Wagga.

Species

Distribution in Australia

Sources of vegetative material in NSW

Severity of salinisation at source sites (low/moderate/severe)

Sporobolus virginicus (marine couch)

Coast and some inland depressions

Yamba
Port Macquarie

Severe
Severe

Sporobolus mitchellii
(rats-tail couch,
condamine couch)

Inland

Gongolon
Walgett
Bourke
Fords Bridge

Low
Low
Low
Low

Cynodon dactylon
(common couch grass)

Throughout

Aberdeen

Severe

Paspalum vaginatum (saltwater couch)

Mainly summer rainfall areas

Ootha

Severe

Paspalum distichum
(water couch)

Throughout

Young

Material from an occasionally flooded depression on a moderate/severe site

Preliminary results

On the basis of mean survival data (Fig. 1), accessions of three species, C. dactylon, P. vaginatum and S. virginicus, performed well at both sites. Survival of accessions of P. distichum and S. mitchellii was very low at Manildra but relatively high at Wagga. Variation in survival rates of accessions of S. mitchellii was higher at Wagga than at Manildra.

Figure 1. Mean survival rates of five native couch grass species at sites near Wagga and Manildra. Averages for Sporobolus mitchellii and S. virginicus are derived from four (three at Wagga) and two accessions respectively.

Discussion

Survival rates of C. dactylon (a common species on saline sites) and P. vaginatum were high as was expected from previous reports (e.g. Truong and Roberts 1992; Semple, Cole and Koen, unpubl. data). High survival rates of S. virginicus accessions in habitats far removed from those at their source were higher than expected – though this species does occurs occur cm at some saline sites in inland Victoria (Victoria Flora Database).

The potential use of the more variably-performing species, P. distichum and S. mitchellii, may be limited to those sites that experience occasional (non-saline) waterlogging, a feature of their natural habitats and which also occurred at the Wagga experimental site. However, high variability between the accessions of S. mitchellii, particularly at the Wagga site, suggests that some “varieties” of this species may have higher salt tolerance than suggested by the results reported here.

A limited number of potentially useful perennial native grasses were evaluated in this trial. Overseas research (Yensen 1999) suggests that Distichlis distichophylla, a native of inland and coastal Victoria, is likely to perform well on very saline sites. However, as with all the species (except C. dactylon) evaluated in this trial, it apparently does not produce viable seed and requires vegetative propagation. Vegetative material of P. vaginatum and S. virginicus is commercially available but planting out over large areas could be expensive.

The availability of species, which could be established from seed, would be a useful option for broad scale revegetation. Salt-tolerant native grasses that apparently produce viable seed include Enteropogon acicularis and Austrodanthonia richardsonii (Rogers et al. 1996), Diplachne fusca (Warwick 1994), Sporobolus caroli and Chloris truncata (Semple and Waterhouse 1994). However, field experience with sowing warm-season species on saline sites suggests that obtaining acceptable germination rates may be difficult (Semple, Cole and Koen, unpubl. data).

To overcome inherent soil variability at saline sites, a mix of species is desirable; and for year-round groundcover and/or production, cool-season species will also need to be evaluated and made available. In addition to salt tolerance, other attributes, cm such as performance when grazed or used as turf, will need to be evaluated.

Conclusion

Cynodon dactylon, Sporobolus virginicus and Paspalum vaginatum had high rates of survival at the two saline sites where they were evaluated. Survival of Paspalum distichum and Sporobolus mitchellii was low at Manildra but relatively high at Wagga, possibly due to a period of waterlogging at the Wagga site. As survivals of the accessions of Sporobolus mitchellii were quite variable, further evaluation of a wider range of material of this species is recommended.

The results reported here constitute a preliminary evaluation of native grasses for saline conditions. Cool-season species, as well as warm-season species that can be established from seed, also need to be evaluated in the field. Although it is hoped that native species will replace exotic grasses in lists of recommended revegetation species, this will not eventuate unless funding organisations are made aware of the potential of native grasses for revegetation.

Acknowledgments

We wish to thank Mr. Pat Clowry for continuing use of his land near Manildra, DLWC colleagues who collected Sporobolus material from western and coastal NSW, and Dr. Donna Windsor for constructive comments on the manuscript.

References

Barrett-Lennard, E.G. and Malcolm, C.V. (1995). Saltland Pastures in Australia. Department of Agriculture: South Perth.

Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1981). Plants of Western New South Wales. NSW Government Printing Office: Sydney.

FitzGerald, D. and Fogarty, P. (1992). Species for saline soils on the Northern Tablelands. In: Seventh Annual Conference of the Grassland Society of NSW (Ed. D. Michalk), pp. 91-92.

Harden, G.J. (Ed.) (1993). Flora of New South Wales Vol. 4. NSW University Press: Kensington.

Malcolm, C.V. and Lloyd, M.J. (2001). Revegetation of one million hectares of wheatbelt saltland in Western Australia. In: Wanted Sustainable Futures for Saline Land. Seventh National Productive Use and Rehabilitation of Saline Land Conference, Launceston, 20-23 March 2001, pp. 124-30.

Matters, J. and Bozon, J. (1989). Spotting Soil Salting. A Victorian Guide to Salt Indicator Plants. Conservation, Forests and Lands: Melbourne.

Rogers, M.E., Noble, C.L. and Pederick, R.J. (1996). Identifying suitable grass species for saline areas. Aust. J. Exp. Agric. 36, 197-202.

Semple, W.S. (1996). Plants of seepage scalds in the Central West and some relationships with soil properties. In: Saline seepage scalds in the Central West of NSW, Technical Report No. 29, Department of Land and Water Conservation (Ed. W.S. Semple), pp. 68-77.

Semple, W.S. and Koen, T.B. (1998). Seepage scalds: rehabilitate or just revegetate? Natural Resource Management 1(1), 18-24.

Semple, W.S and Waterhouse, D.B. (1994). Performance of halophytes from semi-arid areas on two saline seepage scalds of the Central Western Slopes of NSW. Cunninghamia 3(3), 595-608.

Truong, P.N. and Roberts, M.H. (1992). Salt tolerance of some tropical and subtropical grass species grown in Queensland. In: National Workshop on Productive Use of Saline Land, Adelaide, 22-24 September 1992, pp. 36-44.

Warwick, N.W.M. (1994). Diplachne fusca – a potential pasture species for reclamation of saline soils. In: Third National Workshop on Productive Use of Saline Lands, Echuca, 15-17 March 1994, pp. 43-49.

Yensen, N.P. (1999). New horizons in the use of saline resources. In: Salt Management in Action. Productive Use and Rehabilitation of Saline Lands Conference, Naracoorte, 1-5 November 1999, p. 57.

Previous PageTop Of PageNext Page