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Unit 6 - Do the $$$'s stack up?
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SOLUTION 8

Temperate perennial grasses with limited salinity tolerance

 

8.3  What are the benefits from temperate perennial grasses?

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Pasture production

The best gains to be made economically are from renovating the least saline land and phalaris and tall fescue are the most productive of the temperate perennial pasture grasses across much of the medium and higher rainfall zone of southern inland Australia. Phalaris in particular is the most commonly sown of the temperate perennial grasses because of its drought tolerance and adaptability to a wide range of soil and climatic conditions. Tall fescue is less hardy, requiring slightly better soils or slightly higher rainfall to be as productive and persistent as phalaris.

In the absence of salinity, dryland phalaris or tall fescue-based pastures can produce >8 tDM/ha in the higher rainfall, higher altitude areas, and 4-6 tDM/ha in the medium rainfall, lower altitude zones. About 50% of this growth is produced in spring across most districts – in northern, more summer rainfall environments, these species produce significant summer feed, while in southern, winter dominant rainfall zones, summer dormancy and more active autumn growth are expected.

For both phalaris and tall fescue, production falls substantially as salinity increases. When salinity levels exceed about 8 dS/m, production can be negligible, partly because of the direct effect of the salinity on these grasses, and partly because of strong competition from other, more salt-tolerant species. This competition may come from species such as tall wheatgrass that were sown as part of a shotgun mix, or from ‘weed’ species such as sea barleygrass.

The overall impact on pasture production is likely to be that at the lowest salinity levels, production can be significantly increased due to the better water supply and therefore growing season length, but as salinity increases further towards more moderate levels, these temperate perennial grasses become uncompetitive and are quickly crowded out by other species. Research results from a saline site at Gumble in NSW showed that that on a low to moderate salinity site, pasture production of 3 t DM/ha was possible with up to 50% of this coming from phalaris.

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Water use

The water use of these temperate perennial grass species has been widely studied since the issue of dryland salinity started to become significant in the 1980s. The replacement of annual pastures with perennials (principally the temperate perennial grasses and lucerne) across large areas of the medium and higher rainfall zones of southern Australia was strongly advocated and indeed supported with public funding. These perennial- based pastures use more water upthe catchment than annuals and therefore reduce the potential for dryland salinity to further spreadin catchments with local groundwater flow systems. This was seen as a win:win because these perennial pastures are also more productive than the annuals they replaced.

Despite the fact that there is very little information available as to how the water use of phalaris or tall fescue is affected by dryland salinity, we can draw some inferences. The documented ability of phalaris and tall fescue to use soil water for an extended period of the year in non-saline situation probably applies equally well to those mildly saline sites where these species are suited. This applies even more so to the land surrounding saline sites where increased water use can assist in reducing the rate of salinity build-up on the discharge site. Lucerne, which has a greater ability to utilise soil moisture than the perennial grasses, is also well suited to the fringes of saline areas where there is excess water, but low salinity and limited waterlogging. The fact that pasture production and carrying capacity of some mild saltland can exceed that from adjacent, non-saline land clearly indicates that additional water is being accessed and used by these perennial species. For more information, see SGSL Insights product for Andrew Southwell’s story, Lachlan catchment, NSW.

Water use on these saline sites (as on non-saline sites) is a function of the amount of green, transpiring leaf that is present. Therefore, if phalaris and/or tall fescue are actively growing on saltland, they will be actively using water. The tendency for phalaris to go dormant over summer limits its ability to use water and to dry the site out prior to the next wet/winter season, but it does give the plant extreme drought tolerance.

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Amenity & environmental

Lucerne and the temperate perennial grasses have been widely sown in southern Australia to assist with slowing the rate of spread of dryland salinity by lowering watertables. Much of the work of the CRC Dryland Salinity was focussed on the goal of increasing the ‘perenniality’ of agriculture to achieve a more sustainable water balance in the landscape.

However, of more immediate interest here is the potential for saltland pastures (based on the temperate perennial grasses with low salinity tolerance) to provide amenity and environmental benefits for areas already affected by dryland salinity. 

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 20 hectares per farm but in the eastern states it is more likely to be 10 hectares), and partly because saltland is a highly visible ‘blight’ on the farm landscape and can be seen as indicating poor farm management.

Groundcover is the key to most of the amenity and environmental benefits from revegetating saltland. For the environment this involves reducing surface soil evaporation and salt build-up, protecting the soil from erosion, and as the basis for re-establishing some plant and animal biodiversity. Amenity value comes from establishing green and growing plants on previously bare or weedy saline scalds.

Saline sites where phalaris or tall fescue are suitable options will not usually be bare unless they have been seriously overgrazed – more likely, the site will have been invaded by waterlogging or salt-tolerant weed species such as rushes or sea barleygrass. Even if the site is bare, and if groundcover and amenity are the primary motivations behind rehabilitating the saltland that is suited to phalaris or tall fescue, then there are cheaper alternatives such as fencing and conservative grazing without the expense associated with pasture establishment.  These species should only be sown if the motivation is establishing a productive pasture on the saltland as they may present a weed risk if not grazed.

There is increasing recognition of the role that saltland pastures can play in improving catchment outcomes. This is translating into institutional support for saltland pastures, including the temperate perennial grasses, because of the environmental and amenity values they provide. Many organisations that support both agriculture and natural resource management are providing financial support and technical assistance to farmers to assess their saltland, and to revegetate it for productive or conservation purposes. Such assistance is on a state by state or catchment by catchment basis, so local enquiry is essential.

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How do the $$$s stack up?

There are no research results that specifically examine the profitability of establishing temperate perennial grasses with low salinity tolerance on saltland. However, the SGSL program examined the economics of a wide range of potential saltland pasture systems across all the southern states, and concluded:

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. The extent to which farmers can achieve the increases in profit suggested by this study will depend critically on their ability to manage the livestock enterprise to achieve the production levels assumed. Pasture quality and growth were shown to have a major effect on the profitability of improved pastures. Maintaining pasture quality of perennial species requires good grazing management, as long periods of deferment will lead to substantial reductions in feed value.

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Applying this general conclusion to saline sites where phalaris and/or tall fescue are suited suggests that saltland pastures can be very profitable. As indicated in the Andrew Southwell case study under the right conditions, such pastures can be more productive than neighbouring, non-saline pastures. The risk for phalaris and tall fescue is that if the conditions are not right (too saline or waterlogged), then production and profitability will be dramatically reduced.

The NSW SGSL network commissioned an economic evaluation of some on-farm saltland pasture systems, including one where tall fescue was part of the shotgun mix.

NSW economic assessment of saltland pasture establishment


A moderate sized farm in the Boorowa catchment of central NSW where almost 10% of the farm is salt affected was assessed. The soils are from shale/slate parent material, relatively low fertility and not suited to cropping due to susceptibility to sheet and gully erosion.

The analysis used a partial discounted cash flow budget to assess the net present value of cash flows from the investment in saltland pasture. The analysis presented here does not account for the unique benefit the producer may get from the out-of-season value of the feed, nor does it factor in any environmental benefits associated with improving the site and reduction in further land degradation or stream pollution.

The Site and Establishment Process

Farm and Site information. 

  • Farm size – 520 ha; 40 ha salt affected; this site 16 ha, 6 ha salt affected; 750 mm rainfall  

Establishment Process (total $434/ha).

  • Site lightly scarified, harrowed,
  • Sown in May 2004 Lime/Gypsum Jan-May
  • Gypsum applied to scald @ 1t/ha, paddock limed @ 2.5 t/ha
  • Turkey litter @ $22.17/m3
  • Seed mix 21kg/ha, 4 kg tall wheatgrass 3 kg Riverina sub clover 3 kg Quantum Fescue 1 kg Palestine strawberry clover 2 kg puccinellia 1 kg Prop white clover 2 kg Landmaster phalaris
  • Direct drilled with 100 kg/ha Starter 16  
  • Contracted sowing at $50/ha
  • Not sprayed protecting existing native pastures and to retain groundcover (wiregrass, Danthonia, Microleana)  

Maintenance

  • Fertiliser 100 kg/ha DAP

Motivation

  • Farmer felt that rehabilitation was possible
  • To improve aesthetic value by eliminating the bare dirt/scald
  • Mix of production and environmental benefits envisaged

On a cumulative basis, cash flows were positive after year 7 – ie time to break even after accounting for tax on returns and interest payments on the overdraft.


  

Summary - the establishment of saltland pasture on this site was found to be mildly profitable with the assumptions used. The project was cash flow positive in year 4 and was able to pay back the establishment costs by year 7. However, sensitivity analysis suggests the high costs associated with pasture establishment make profitability dependent upon good pasture and grazing management (7 dse/ha required) to ensure high levels of pasture production and utilisation, pasture persistence (10 years required) and better than long term average prices for products.

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