Dealing with salinity in Wheatbelt Valleys - Department of Water

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In summary the picture is one of an agriculture that does not have the capacity to finance large-scale change. However there are also indications that some past downward trends in the Wheatbelt economy may be stabilising, reinforcing the region’s ongoing role as a major contributor to the economy and community of Western Australia. WHY PERENNIALS? Perennial plants invest a large proportion of their resources to develop deep root systems and so get access to deeply infiltrating water. Access to deep moisture permits a longer active growing season and greater water use than can be achieved by annual plants. Salinity researchers agree that perennials will eliminate recharge over the area on which they stand where annual rainfall is less than 600 mm. There is however debate about whether relatively small areas of perennial plants might intercept significant surface and subsurface flows of water from adjacent annual crops or pastures. Hatton & George (2001) review the circumstances where this will occur. The extent to which water will move to trees is favoured by sloping land, less saline groundwater, thinner regolith (
Porter, Bartle and Cooper Table 5: A classification of perennial plants based on form, use and site preference Woody Plant type and form Grazing Direct-harvest Herbaceous Tree Coppice Seeder Non-legume Legume Woody plants with the ability to coppice (grow back from the cut stump) can be used as short rotation crops that do not need to be replanted after harvest. The native flora is rich in coppicing species. Mallee is an example now under active development as a large scale biomass feedstock crop. Biomass feedstocks show promise for multiple products including extractives, wood chip and bioenergy. Coppicing species appear generally to be poorly adapted to discharge areas but some mallees and Melaleuca species have good tolerance of salinity and waterlogging and have commercial potential. In all some 40 species of mallee eucalypts and Melaleuca are currently being investigated for their commercial potential. Obligate seeding (non-coppicing) woody plants have potential as phase crops where they can produce biomass feedstocks in rotation with conventional annual crops. The genus Acacia, a major native legume group, shows most promise for this type of crop. It is large seeded and can potentially be mechanically sown thus reducing establishment cost – an imperative for a short-rotation seeder crop. There are woody grazing shrubs for both recharge areas (tagasaste) and discharge areas (saltbushes). The herbaceous perennials will most commonly be grazing plants like the legume lucerne or non-legume grasses. As with grazing shrubs, this category has the significant advantage that they supply already existing industries. They therefore do not face the considerable development costs of direct harvest species where all harvest, transport, processing and marketing operations must be built from scratch. Lucerne is the herbaceous perennial at the most advanced stage of development as a component of WA farming systems. There are many herbaceous perennials other than lucerne. G. Moore (unpubl. data) listed over 100 genotypes as potential subjects Recharge Discharge Recharge Discharge – 6 – for investigation of their suitability for the WA Wheatbelt. A range of sub tropical perennial legumes could also be used. Ten-year old stands of Siratro and Lotononis in the West Midlands have survived the driest summers on record (T. Wiley, pers. comm.). The Cooperative Research Centre for Plant-based Management of Dryland Salinity has established a sub-program to identify and evaluate potential species. While most of the focus of this paper is on perennial plants capable of growing in recharge areas in the landscape, the recharge areas form a significant and growing part of the Wheatbelt. Land affected by high watertables varies in its potential to support plant growth. Barrett-Lennard et al. (1999) divided such land into three broad classes – land of ‘high’, ‘moderate’ and ‘low’ productivity on the basis of position in the landscape, soil texture, and the severity of salinity, waterlogging and inundation. Barrett-Lennard (2001) speculates that saltland rated as ‘high’ productivity (shallow brackish groundwater – about 20% of WA’s saltland) may be recognised as the most profitable land on the farm. He suggests it could be used for the growth of high value wood and horticultural crops. Land of ‘moderate’ productivity (duplex moderately saline and waterlogged land – about 40% of WA’s saltland) may be used for the growth of mixtures of halophytic forage shrubs with annual understorey species. These pastures could be used for the grazing of sheep and perhaps cattle. Land of ‘low’ potential (highly saline, waterlogged – about 40% of WA’s saltland) will be mostly only suitable for the growth of samphire species. Together with aquaculture and other more intensive land uses, these industries have been referred to as the PURSL (Productive Use and Rehabilitation of Saline Land) options. The range of these options is still developing. Yensen (2000, cited by E. Barrett- Lennard, pers. comm.) estimated that there are
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Foreword Dealing with Salinity in W
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1Day one: Monday 30th July. Field t
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Papers Dealing with Salinity in Whe
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Ali and Coles biggest challenges fa
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Ali and Coles erosion, maintenance
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Ali and Coles expected under these
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Ali and Coles Coles, N.A. & Ali, M.
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Commander, Schoknecht, Verboom and
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APPRECIATING AND CREATING OUR HISTO
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services. The Government responded
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WHEATBELT VALLEYS IN DIFFICULTIES T
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argue that they were really abnorma
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1990s, the wheatbelt valleys in par
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REFERENCES Agstats (1997). Agricult
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George and Coleman two to four fold
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George and Coleman surface, the vas
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George and Coleman for example in t
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George and Coleman current trends c
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George and Coleman While not as div
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George and Coleman SPECIES Table 5:
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George and Coleman advantages of so
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George and Coleman this volume). In
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George and Coleman Venture Economy
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George and Coleman Lawrence, C. (19
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Hatton and Ruprecht WATCHING THE RI
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Since the mid 1970s annual rainfall
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Effect of clearing on runoff The ot
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Salinity Monthly streamflow (ML) 10
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The ratio of the salt outputs to in
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- 11 - Hatton and Ruprecht Table 4:
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Page 105 and 106: INTRODUCTION The Lake Chinocup Catc
Page 107 and 108: agriculture) in various stages, the
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Page 117 and 118: eliminates drainage through the nex
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Page 131 and 132: Pannell Pannell, D.J. (2001). Dryla
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with Salinity in Wheatbelt Valleys
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Photo Gallery 2 Dealing with Salini
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APPENDIX 1 BACKGROUND HYDROLOGY AND
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WHEATBELT HYDROLOGY Flow in the Yil
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Flow (ML) STREAM SALINITY Salt Rive
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APPENDIX 2 WATER MANAGEMENT OPTIONS
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APPENDIX 3 MANAGING WATER AND SALIN
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SUMMARY- TIMELINE OF RECENT SIGNIFI
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RECENT HISTORY OF WATER AND SALINIT
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Figure 1. Hydrological cross-sectio
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Depth (m) 316 315 314 313 312 311 M
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FURTHER INVESTIGATIONS AND MANAGEME
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Dealing with salinity in Wheatbelt Valleys - Department of Water

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