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SOLUTION 7

Vegetatively established grasses

 

7.3  What are the benefits from vegetatively established grasses?

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Production

Few scientific data are available about the production potential of these vegetatively established grass species and almost no information is available about animal performance.

Farmers report that both sheep and cattle will effectively graze the vegetatively established grasses but there is little documented information on the levels of animal production that can be expected. Often saline sites remain wet and therefore actively growing when the rest of the farm contains only dry, carry over feed – this greatly increases the ‘value’ that any saltland pastures can contribute in a whole farm system.

During the period 2002 to 2007, some limited research was undertaken on marine and saltwater couch in NSW and Victoria.

Two scalded saline sites on the inland slopes of NSW (Wagga Wagga and Manildra) were selected for an evaluation of ten accessions of warm-season stoloniferous/rhizomatous grass species, including marine couch and saltwater couch. Most species performed well at Wagga Wagga but only common couch, marine couch and saltwater couch performed at Manildra, where they consistently outperformed the other native species in terms of survival, groundcover and vigour. Saltwater couch had the highest mean vegetative cover at both sites. Overall production was not high – of the order of 1t/ha over the growing season - though this research was carried out during dry years and probably considerably under estimates the potential of these species in wetter conditions.

In Victoria, the Sustainable Grazing on Saline Lands (SGSL) research site was located near Hamilton. While the vegetative grasses were not specifically included in the project, the control plots (or volunteer pasture) included a significant proportion of saltwater couch. The two figures below (Figure 7.9 and 7.10) show the pasture and animal performance from the sown (saltland species and persian clover) and the saltwater couch and volunteer pastures. In summary, the volunteer pasture with a significant saltwater couch component produced from 2 to 4t/ha of dry matter depending on the salinity of the plots, and this was able to support about half as many grazing as the sown pasture. 


     

Figure 7.9. Pasture growth of saltland species and persian clover sown compared with a saltwater couch based volunteer pasture at the Hamilton sites between April and December 2003 and in relation to topsoil salinity measured in December 2003.



   

Figure 7.10. Mean stocking rate for the sown and saltwater couch/volunteer pastures in relation to topsoil salinity.

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Water use

There is no information available regarding the water use by the vegetatively established grasses. However, these are grasses that grow actively on saline and waterlogged sites, and they are active during the warmer seasons when water use can be expected to be high – this will be especially true if there is good groundcover and a high leaf area index (ratio of leaf area to soil surface area).

We can draw inferences about the vegetatively established grasses because during the SGSL initiative, water use was studied at several research sites across southern Australia, albeit with other saltland pasture species. When combined with other knowledge, we can now conclude:

  1. Saltland pastures can have a significant effect on local hydrology (ie salt and water movement), primarily because there is an increase in evapo-transpiration under well managed saltland pastures compared to untreated controls. This results in a reduction in waterlogging and average soil moisture content above the watertable in the saltland pasture relative to neighbouring unpastured saltland. In addition, there are clear indications that under favourable circumstances (watertable shallow but not overly saline) saltbush (and possibly other perennial saltland species) can draw directly from the groundwater and therefore lower the watertable in catchments with local groundwater flow systems.
     
  2. As a result of the lower water content (and possibly lower watertable), the salt content of the upper soil layers can be reduced by leaching, making sites potentially more suitable for the growth of less salt- tolerant, but more productive and nutritious under-storey species. Most research on this topic has been done with saltbush stands that draw down the watertable and can support a less salt-tolerant legume/grass under-storey, but there is some evidence that Distichlis can act in a similar way
     
  3. Trees will use more water (soil water and from the watertable) than pastures if the groundwater is not so saline as to prevent roots from accessing it. Direct comparisons between saltland pastures and trees are rare, but work in central NSW has confirmed that trees on saltland in local groundwater flow systems can increase water use and lower the watertable which should dramatically reduce surface run-off and salt export from saline sites.
     
  4. Within saltland pastures, water use will tend to be lowest from annual species and those perennials (such as puccinellia) that dry off over summer, and greatest by summer-green perennial pasture species (such as saltbush, tall wheatgrass and the vegetatively established grasses) that grow actively over summer.
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Amenity & environmental

As with the other potential benefits that may be associated with vegetatively established grasses on saltland, there is little or no scientific information available so we have to draw the likely inferences from other saltland pasture species and situations. 

Farmer case studies have consistently shown that while profitability is the major consideration in the way successful farmers run their businesses, it rarely dominates the decisions associated with managing saltland. This is partly because most farms have salinity on only relatively small areas (the national average is about 20ha but in the eastern states it is more likely to be 10ha), and partly because saltland can be a highly visible ‘blight’ on the farm landscape.

The key to most of the amenity and environmental benefits from revegetating saltland lies in increasing groundcover. This has the benefit of reducing surface soil evaporation and salt build-up, protecting the soil from erosion, and re-establishing some floral and faunal biodiversity. For improved amenity it involves establishing green and growing plants on previously bare saline scalds.

Marine couch, saltwater couch and Distichlis are all used as turf (or amenity) grasses because of their ability to colonise saline sites, and to establish a full mat of groundcover so their amenity value is presumably high! Research shows that these three halophytic genotypes have better ability than kikuyu to remain green under saline conditions.

The differences between vegetated and unvegetated areas within a single saltland area can be extreme. Data from the SGSL sites has shown that when soil salinity increases and/or in the absence of vegetation, soil microbial activity and biomass are reduced, being almost zero (lowest ever recorded by the laboratory) in soil from bare saline sites. However, in the presence of vegetation, even if the measured salinity is the same, microbial activity is about an order of magnitude higher, but still substantially below the levels found in non-salt-affected pastures. Other research has shown that where Distichlis had been growing for 8 years, there were significant improvements in the chemical and physical health of the soil. In other words, the link between improved groundcover and better soil health on saline sites is clear.

From this information, it is easy to conclude that the vegetatively established grasses when allowed to colonise a saline site and grazed conservatively to ensure good groundcover is maintained, can provide a significant boost to both the environmental health of the site and to the visual amenity.

There is increasing institutional support for saltland pastures, including the vegetatively established grasses because of the environmental benefits and amenity they provide. Many organisations that support both agriculture and natural resource management are providing financial support and technical assistance to help farmers assess their saltland, and revegetate it for productive or conservation purposes. Such assistance is on a catchment by catchment basis, so local enquiry is essential.

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How do the $$$s stack up?

We have been unable to find any independent economic analyses that detail the paddock-scale costs and returns from these vegetatively established saltland grasses. This does not mean that some general conclusions cannot be drawn from the combination of farmer experiences and economic analyses of other saltland pastures where more detailed studies have been made.

The Sustainable Grazing on Saline Land (SGSL) program showed that across southern Australia, saltland pastures could provide a profitable investment. The final report from the SGSL Economics Theme stated “Introducing improved pasture species to salt-affected land to increase the feed value for livestock is profitable across a broad range of environments, production conditions and commodity price assumptions, according to the results of this study.

However, the profitability of saltland pastures is complex because up to half the benefits typically come from saltland pastures providing ‘support’ for the cropping and grazing on the rest of the farm. This may be out-of-season feed allowing a higher stocking rate across the rest of the farm; the additional grazing resource allowing more cropping while maintaining stock numbers; shelter (at least with saltbush) for lambs or off-shears sheep when they are most vulnerable to the elements; and increased value of their real estate when the salinity problem is seen to be manageable. In addition, many farmers establish saltland pasture to improve the amenity of their working and living environment and to achieve that aim, they will accept a lower rate of return than they would demand from other on-farm investments.

Notwithstanding these benefits, the SGSL program clearly identified several factors that can undermine the profitability from saltland pastures, and we can apply these general conclusions to the vegetatively established grasses:

  • Infrastructure costs can be a major factor for any saltland pasture if fencing and water are required for a small site where there are only few hectares to absorb overheads;
     
  • Establishment costs are a primary determinant of profitability and can vary greatly for different saltland systems (in the SGSL program, the variation across 20 farm sites in WA was from $77 to $324/ha). In general, the costs of establishing a saltland pasture are similar to a non-saline pasture if sown from seed, but will tend to be significantly higher for vegetatively established grasses or for saltbush seedling;
     
  • Risk of failure is significantly higher than for non-saline pastures, particularly if the site is waterlogged or sodic (as is often the case) as well as being saline. Because these vegetatively established species do not have to start from seed, the risk of failure is probably lower than for some other saltland options;
     
  • Pasture productivity – in general terms, the saltier the site, the lower the pasture and animal production that can be expected (see Figures 7.9 and 7.10 above). Given that the most likely situation for the vegetatively established grasses is in highly saline and waterlogged areas, any assumptions regarding the level of pasture production that might be achieved should be kept modest. That said, a marine couch-based pasture at Hamilton (see Section 7.3a) produced 2-4 tonnes of dry matter per hectare, and anecdotal evidence from Queensland (where marine and saltwater couch are widely used on saltland) indicates that in the warmer regions, these pastures can produce a significant amount of forage;
     
  • Nutritive value of the pasture – many saltland species either accumulate salt, or have unusual compounds in the leaves that help them survive the inhospitable saline environment, but these can be detrimental to grazing animals. The vegetatively established grasses do not have any of these limitations so nutritionally, we can expect them to be similar to their non salt-tolerant relatives;
     
  • Product prices – the cost of ongoing inputs such as fertiliser or supplements and the prices paid for meat and wool products will always impact on the ‘bottom line’ of any pasture system and the vegetatively established grasses are no exception.

In conclusion, the vegetatively established grasses are a high cost option for saltland, and because of their suitability to highly saline and waterlogged areas, production levels will usually be modest. These grasses are most suited to small saltland sites where amenity and environmental improvements are the primary expectation, rather than grazing value and profit.

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