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UNIT 7

Saltland Toolbox

 

7.5  Pasture & revegetation options

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There are 11 discrete options (or saltland solutions) that are now available for farmers wanting to ‘improve’ their saltland, for production, for conservation, or for amenity value. One of the core capabilities that Saltland Genie brings to this website is the ability to assist with both reviewing the 11 saltland solutions in general [Comparison engine] and to help match a particular saltland site with one or more of the most appropriate solutions.

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Saltland Solution 1 - Fence & exclude from grazing

Saltland Solution 1 - Fence and exclude from grazing is recommended for sites that that are too saline, waterlogged and/or inundated for other solutions to succeed.

Such sites are best suited to the growth of samphire (Halosarcia species of which there are several that all go by the common name samphire), although other highly salinity and waterlogging plants may be present – such as curly ryegrass, cotula, pig-face, sea blight – and salt-tolerant trees such as salt paperbark (Melaleuca halmaturorum) and swamp sheoak (Casuarina obesa). Revegetation of this class of land is gradual and episodic, and occurs naturally if grazing is excluded. Samphire itself is not suited to grazing as the salt concentrations in the forage can reach concentrations of 40% and there are likely to be other, anti-nutritional factors.

The objective behind this saltland solution may be to protect a site that has existing conservation value, but could also be about revegetation to decrease soil erosion, mitigate the severity of flash flooding and/or increase amenity values. These sites have no current commercial value, nor any commercial prospects.

Where is this option likely to be best suited?

Samphires are endemic across southern Australia and therefore are well adapted to that range of temperature and rainfall conditions. Samphire habitats traditionally included salt lakes and pans, salt marshes and coastal flats, but have now expanded into areas of secondary salinisation.

Samphires are highly salt-tolerant once established and typically of halophytes, the pattern of growth is lower when salinity is low, increasing to an optimum with an ECe of ~10 dS/m, and then gradually declining as ECe values reach 40 dS/m. Samphires can grow in soils that are more or less permanently waterlogged in winter, and some species can withstand up to 6 months partial inundation. The seeds are not highly salt-tolerant and successful germination requires that soils be leached by rainfall and/or flood waters before germination occurs.

Special features or challenges

Because there is no prospect of a financial return from fencing off saline land and excluding grazing, cost management is a major factor. In some regions, financial support for fencing off ‘revegetation or conservation’ areas is available from regional NRM Boards or Catchment Management Authorities.

When a saline site is protected from grazing, samphire will inevitably occupy the most severely affected saltland, given sufficient time – this process can be speeded up by bringing in material from other sites.

Farmers wanting to assist the establishment of samphire on their suitable saline land, are best advised to harvest the shoots of local plants by hand or with a forage harvester, and spread the harvested material on the ground.

Samphire should not be grazed because of the extremely high salt concentration in the leaves, and the land supporting this saltland system will be very fragile.

Likely benefits from this saltland solution

Improvement in visual amenity and erosion control are likely to be the primary motivations behind farmers revegetating this highly to extremely saline and waterlogged land. Under suitable conditions (extreme salinity and high waterlogging), samphire will colonise the site and provide groundcover which can be a significant improvement to visual amenity.

Saltland Solution 1 – Fence and exclude from grazing

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Saltland Solution 2 – Fence & volunteer pasture

Saltland Solution 2 - Fence and volunteer pasture is recommended across a wide range of saltland situations – but not for the most severely affected saltland (saline and waterlogged) where Saltland Solution 1 –Fence and exclude from grazing, is the best option.

The potential value of this saltland solution was highlighted across the Sustainable Grazing on Saline Land (SGSL) initiative research and grower network sites where all trials had a ‘treatment’ the farmer group wished to test, and a ‘control’. These ‘control’ areas were fenced off and grazed rotationally which resulted in significant improvements in groundcover and productivity. Better still, the costs associated with the control plots were minimal (fencing only) and the risk of ‘failure’ was reduced to almost zero. Across the SGSL research sites, the general conclusion was that this ‘fence and volunteer pasture’ option was capable of a production level of about 60% of that achieved on nearby, non-saline land.

The objective behind this saltland solution is to protect saltland from overgrazing, and to bring it back into productive use without the cost and risk associated with sowing a saltland pasture. Implementing this saltland solution does not preclude the opportunity to sow a saltland pasture at a later stage if the pasture that volunteers is disappointing.

Where is this option likely to be best suited

This saltland solution is suitable for all saltland that is of low (subsoil ECe of 2-4 dS/m), moderate (subsoil ECe of 4-8 dS/m), or high salinity (subsoil ECe of 8-16 dS/m). That is, any situation where a sown saltland pasture might be considered. At severe salinity levels (subsoil ECe of >16 dS/m), it is likely that the ‘volunteer’ species will be samphire; this is not suitable for grazing and this solution effectively becomes Saltland Solution 1 – Fence and exclude from grazing.

There are two additional considerations:

  1. As soil salinity increases from low to high, the additional pasture production from a sown saltland pasture compared to a volunteer pasture tends to decline, and at the highest salinity levels, not only will overall production be low, but the volunteer species will be as productive as sown species. Therefore at higher salinity levels, it is more difficult for a sown saltland pasture to be profitable, and therefore the ‘fence and volunteer pasture’ option can be a better bet.
     
  2. Whole farm economic modelling undertaken as part of SGSL showed that in the higher rainfall areas (that predominate in south-eastern Australia) ‘fence and volunteer pasture’ often provided a better economic return than sown pastures because the volunteer pastures tended to contain perennial species that provided summer feed. In contrast, for drier areas (that predominate in the wheatbelt of WA), while ‘fence and volunteer pasture’ provided a positive return, the volunteer pasture tended to be annual species and better profits could be achieved with options such as saltbush and under-storey that provide green feed in autumn.

This analysis suggests that the ‘fence and volunteer pasture’ option is suited to:

  • farms where the areas of saltland are too small to make a significant contribution to the farm feed supply – other non-grazing options should also be considered in this situation;
  • climatic zones where perennials rather than annuals are likely to establish;
  • any sites where the risk of failure with sown saltland pasture is thought to be high;
  • sites where available funds allow fencing but not pasture improvement;
  • sites where the farmer does not have the time or skills to establish a saltland pasture.

Special features or challenges

The most important feature of ‘fence and volunteer pasture’ is that a farmer can avoid both the cost associated with establishing a saltland pasture and the risks associated with either establishment failure, failure of the sown pasture to produce at a high enough level to return a profit, or failure of the pasture to persist for long enough to break even.

The conclusion from the SGSL initiative was that there are almost no situations where ‘fence and volunteer pasture’ is not a viable option for saltland – something always grows! In some situations, other options will be more profitable, or may better meet the farmer’s objectives, but implementing ‘fence and volunteer pasture’ does not prevent a farmer from implementing other saltland solutions if the volunteer pasture does not meet expectations.

The main ‘risks’ associated with ‘fence and volunteer pasture’ are: (a) the fact that the volunteer pasture that establishes will likely be less productive and/or less nutritious, and maybe less profitable than if a ‘proper’ saltland pasture was established, and (b) that the volunteer pasture will include significant weeds such as spiny rush; if this is the case, and weed control is needed, then the cost of the option will be increased.

Likely benefits from this saltland solution

Across a wide range of saltland sites, the information from SGSL indicated that ‘fence and volunteer pasture’ could provide approximately 60% of the production achieved on nearby non-saline paddocks. While it may be more than 60% for high capability sites, and less for low capability sites, the 60% rule of thumb is a good place to start.

Using whole farm economic modelling this option was examined for sites in WA, SA and NSW and different conclusions emerged for the wheatbelt of WA, compared to the eastern states. In the more temperate and summer rainfall areas from SA through to NSW, the best marginal returns were from simply fencing off saltland and allowing a volunteer pasture to establish, while in the summer dry areas of WA the reverse was true – there was a small increase in whole farm profit from simply fencing the saltland but a larger profit was generated by saltbush and understorey pasture.

While there is no research information available, farmer experiences suggest that ‘fence and volunteer pasture’ can also deliver significant amenity improvements as the volunteer pasture replaces what are often bare or overgrazed salt scalds. 

Saltland Solution 2 – ‘Fence and volunteer pasture’

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Saltland Solution 3 – Dense saltbush plantings

Saltland Solution 3 – Dense saltbush plantings option refers to the growth of saltbush in dense (>1,000 stems/ha) plantations. These dense plantings are established as nursery raised seedlings (lower risk but higher cost) or direct seeding (higher risk but lower cost). These dense plantings all have some volunteer annual under-storey but the density of the planting severely limits the opportunity for under-storey species.

Saltbushes are woody shrubs with leaves that accumulate significant amounts of salt that is noticeable when tasted. The saltbushes are all Atriplex species, with the main ones used for saltland pastures being old man and river saltbush (Australian natives), and wavy leaf saltbush (introduced from Argentina). The dense planting of saltbush was one of the first saltland pastures developed in Australia so both researchers and farmers are reasonably confident in their understanding of this option.

Profitability is typically quite low ~$5-6/ha, but the system has low maintenance costs after establishment and can persist indefinitely as saltbush is very long-lived. Saltbush can be heavily crash- grazed as long as there is sufficient recovery time – many systems are grazed back to the sticks every autumn as saltbush stands are a great place to supplementary feed sheep in autumn without risking soil erosion.

Where is this option likely to be best suited

This option is suited to land of moderate-to-high salinity and low-to-moderate waterlogging in the 250–400mm rainfall zone. Saltbush is a summer grower and has a requirement for average daily temperatures greater than about 10oC. Therefore, it is not recommended for saline sites in the cooler and/or wetter areas across southern Australia.

The saltbushes are the perennial halophytes with the broadest range of adaptation to saltland in southern Australia. The recommended range of ECe values in the subsoil (25–50 cm) for dense plantings of saltbush is 8–16 dS/m. For sites with an average subsoil ECe below 8 dS/m, the recommendation would be for less dense plantings of saltbush with more focus on improved under-storey – as outlined in Saltland Solution 4 – Saltbush and understorey. In addition, average watertables in summer should be deeper than 1 m for densely planted saltbush because saltbush is relatively sensitive to waterlogging and inundation especially if it is prolonged or if it occurs during periods of high temperature.

Dense saltbush plantings are no longer widely recommended because saltbush with under-storey is more profitable, has lower establishment costs, is more productive and nutritious, and generally provides for easier management of sheep.

Special features or challenges

Establishment of saltbush from seed is less reliable than using nursery-raised seedlings. Direct seeding is cheaper (around $100–150 per hectare) than planting of nursery-raised seedlings (around $450 per hectare). However there is a strong soil type influence, with direct seeding much more likely to succeed if there is a ‘sandy’ surface soil. Direct seeding is therefore not recommended on heavy-textured soils.

If saltbush plantings are not grazed frequently enough, the plants will grow out of the reach of grazing sheep and subsequent growth will be concentrated above the sheep grazing height. Grazing cattle can assist in bringing the stand back to sheep grazing height as mechanical pruning/slashing is expensive and can be difficult in dense plantings.

Sheep can be hard to muster in dense saltbush plantings, particularly when the bushes have grown above the height of the sheep.

Likely benefits from this saltland solution

Saltbush has some well established positives as a stock feed - it is green over summer when most other feed is dry; it has high protein levels; it provides vitamin E which can otherwise be a limitation for sheep on dry, autumn pastures; and the salt in the saltbush leaves can improve the efficiency of conversion of feed to wool.

Saltbush has some ability to lower watertables if they are not highly saline and this can allow some leaching of salts out of the surface soil layers, potentially making the site more productive – this benefit is more critical in Saltland Solution 4 – Saltbush and understorey.

By far the most consistently reported environmental benefit from dense saltbush plantings is visual amenity – especially when contrasted with the often sorry state of untreated saltland. 

Saltland Solution 3 – Dense saltbush plantings

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Saltland Solution 4 - Saltbush and under-storey

Saltland Solution 4 Saltbush and under-storey is now the most recommended saltland pasture option for low rainfall (ie low waterlogging) sites, the majority of which occur in the wheatbelt of WA, but with significant opportunities also available in the drier wheat growing regions of SA, Victoria and NSW.

Much of the original published information about saltbush use on saltland was focussed on dense saltbush plantings – typically >1000 saltbush ‘stems’ per hectare. This work focused mainly on mixtures of three saltbush species – old man saltbush (Atriplex nummularia), river saltbush (Atriplex amnicola) and wavy leaf saltbush (Atriplex undulata).

It is now clear that where an annual under-storey between the saltbush rows is possible, the under-storey provides the bulk of the nutrition for grazing animals. Saltbush is usually sown in multiple rows, with a wider alley between the sets of rows for the under-storey – in this configuration, saltbush may have 500 to 600 stems/ha but this can vary quite widely depending on the width of the alley ways. The saltbush species for this option should be old man saltbush – it has higher nutritive value than river saltbush and wavy leaf saltbush.

The saltbush in the ‘saltbush and understorey’ system has two key roles:

  1. Using water over summer to dry out the soil and draw down the watertable so that the surface soil can be more readily leached of salt and therefore support a more productive and nutritious understorey;
     
  2. Providing green feed in autumn, at a time when most farms in the low rainfall zone will have only dry standing feed.

The understorey in the ‘saltbush and understorey’ system also has two key roles:

  1. The primary role is to provide quality feed for livestock;
     
  2. A secondary role is to ensure that the saltland site has good groundcover to minimise the evaporation of water from the soil and the subsequent build-up of salts in the root zone.

The most frequently recommended annual species for sowing as under-storey in a saltbush-based pasture are balansa clover, burr medic and barrel medic, plus annual and Italian ryegrasses.
The objectives behind implementing this saltland solution will usually be a mixture of production/profit and amenity improvement.

Where is this option likely to be best suited

The ‘saltbush and understorey’ option is restricted to sites that will support saltbush and performs best where the site will grow understorey legumes – that is, sites of low to moderate salinity with little or no waterlogging. This means becomes the recommended option for sites of moderate salinity (ECe 4-8 dS/m) in the 250-400mm rainfall zone, but it can also be recommended for sites of low salinity (ECe 2-4 dS/m) if the rainfall is too low to support perennial grasses like tall wheatgrass, tall fescue and phalaris.

For sites with high salinity (ECe 8-16 dS/m), a sown under-storey is unlikely to be more productive than an under-storey of volunteer species and the savings on under-storey seed, sowing and fertilising can be put into a higher density of saltbush.

For wetter sites, with moderate and high salinities, the salt-tolerant grasses (especially tall wheatgrass and puccinellia) provide a more productive and persistent option.

Special features or challenges

The establishment of the saltbush is usually a more challenging task than for the understorey. Planting out nursery-raised saltbush seedlings reduces the risk of failure, but significantly increases the cost. Where direct seeding of saltbush is possible then it provides a significantly cheaper option but this is only recommended for lighter textured soils, or where there is a sandy layer over clay. There is a significant research focus on direct seeding of saltbush so recommendations might change dramatically in the future.

Young saltbush plants, especially if direct seeded, are very susceptible to weed competition and insect attack. Sea barleygrass, annual ryegrass and iceplant are perhaps the most common weeds, while red legged earthmite is a common insect pest. Controlling these pests and weeds to allow the saltbush to establish will automatically improve the situation for the under-storey species.

Most commonly, requires a two-stage operation, with saltbush sown or planted in early spring and the under-storey sown after the opening rains in the following autumn.

Established saltbush stands are very persistent, resisting drought, salinity and frost. The under-storey is more vulnerable because it has to re-establish each year which is more difficult in sites with higher levels of salinity and waterlogging.

Likely benefits from this saltland solution

There is now a considerable body of research evidence and farmer experience to show that ‘saltbush and understorey’ has three main benefits:

  1. Improved whole farm profit from the extra feed produced, particularly if the extra feed can be utilised in autumn and replace hand feeding;
     
  2. Improved visual amenity for the saltland;
     
  3. Environmental benefits in the form of lowered watertables and biodiversity improvements.

Saltland Solution 4 – ‘Saltbush and understorey’

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Saltland Solution 5 - Tall wheatgrass

Saltland Solution 5 - Tall wheatgrass (Thinopyrum ponticum) is a temperate perennial grass tolerant to moderate levels of both salinity and waterlogging. It has been widely used as a saltland pasture in south west Victoria and the upper south east of South Australia – often in a shotgun mix with puccinellia, balansa clover and strawberry clover.

There are two varieties of tall wheatgrass (Dundas and Tyrell) but research has shown them to be similar in yield and salinity tolerance across a range of saline soils in western Victoria. Dundas is the recommended variety because of higher quality for livestock, and for minimising the risk of spread as an environmental weed.

Where is this option likely to be best suited

Tall wheatgrass thrives in conditions that also favour buck’s horn plantain, sea barleygrass and spiny rush – conditions characterised by moderate levels of salinity and waterlogging. Tall wheatgrass is unlikely to be found in saltier environments nor in areas that are inundated for extensive periods during the warmer months; samphire and puccinellia are the options for these more severely affected soils. Tall wheatgrass is tolerant of both acid and alkaline soils.

Tall wheatgrass is generally regarded as a pasture for higher rainfall zones, up to as much as 800 mm, but it is drought-tolerant and it can be used at rainfall levels down to about 425mm/yr. Although a warm season grower, tall wheatgrass is not a sub-tropical species; therefore it is not frost sensitive making it well suited to southern Victoria and South Australia where it is often too cold for saltbush.

It is common for farmers to sow a mix of tall wheatgrass and puccinellia, allowing each to find its niche in heterogeneous saline/waterlogged landscapes – tall wheatgrass will be favoured where the waterlogging is lower, while puccinellia will colonise the more waterlogged areas.

Special features or challenges

Because there has been a significant research input, the strengths (persistence, water use, out-of-season feed) and weaknesses (cost, animal nutrition limitations and weed potential) of tall wheatgrass either as a single species or in a species mix are reasonably well tested and understood.

It is strongly tussock-forming and can quickly become clumpy and unpalatable to livestock. Management of the mature pasture is very important and can mean the difference between a productive sward and paddock that is almost impossible to drive across (because of the large tussocks), is almost completely unpalatable, has low nutrient status, provides no ‘space’ for complementary species, and acts as a source of potential weed seed.

The ready adaptability of tall wheatgrass to a range of Australian conditions has inevitably meant that it can pose a weed problem if not well managed. If allowed to run up to seed it can spread and colonise areas where it is unwanted, particularly along watercourses and roadsides.

The relatively slow establishment of tall wheatgrass often requires that it be allowed to set seed in the first year to thicken up. This implies a further year’s wait for the pasture to come into full production.

Likely benefits from this saltland solution

Under the right conditions, tall wheatgrass based pastures can ‘transform’ non-productive saline land into highly productive and profitable pasture – for this to occur, grazing management must be used to keep the sward short and vegetative.

Like saltbush, tall wheatgrass is a summer grower and therefore has some ability to dry sites out – this can increase the leaching of salts from the surface soil as well as delaying the on-set of waterlogging in the following winter.

Though the visual amenity of tall wheatgrass pastures is considerably higher than for untreated saltland, pasture production is usually the primary motivation behind establishing tall wheatgrass based pastures. 

Saltland Solution 5 – Tall wheatgrass

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Saltland Solution 6 - Puccinellia

Saltland Solution 6 - Puccinellia (Puccinellia ciliata) is a perennial grass that is tolerant to high levels of soil salinity and waterlogging. Along with distichilis and marine couch, it is the most salt-tolerant of the commercially available grasses, and it is the only salt-tolerant, perennial grass suitable for highly saline scalds that are dry in summer.

Though a perennial, the plants hay off in November/December and remain dormant over summer. Nutritive value declines as the plant flowers, matures, senesces and further declines through summer and autumn, though it is still palatable and compares well to other dry feeds.

Often, puccinellia sites are highly waterlogged over winter and during that time, surface soil salinities can be low, potentially making balansa clover a partner. However, both farmer experience and research results show that balansa will perform strongly in the year of sowing but tends not to persist.

Where is this option likely to be best suited

Puccinellia can withstand high to extreme surface soil salinities in summer (ECe values of 10-50 dS/m) because it dries off over that period. It is only recommended in the moderate rainfall zones (> 400mm) across southern Australia, not because of the rainfall per se, but because it is only at these higher rainfall levels that the combination of waterlogging and salinity most suited to puccinellia is likely to occur. Puccinellia is relatively non-competitive outside of those conditions.

Common indicators for the puccinellia zone are sea barleygrass, samphire and curly ryegrass, and there will often be patchy scalding across a site suitable for puccinellia. Though it will tolerate a fairly wide range of soil pH values, puccinellia is particularly suited to alkaline to highly alkaline soils, or at least, it has a stronger competitive ability at those higher pH values.

The ‘ideal situation’ for puccinellia based pastures is in the upper south east of SA, where over 200,000 ha have been established. Uptake has been slow in other states but it is finding more acceptance as part of a shotgun mix of saltland pasture species.

Special features or challenges

Puccinellia is highly palatable and has a low salt concentration in the leaves. It forms tussocks up to 40cm high and wide, and has long, thin leaves. Its growing points are embedded in the base of the plant, which is compact and resistant to grazing.

Mature stands can be grazed after the opening rains (when they rapidly produce green feed) and/or more commonly as dry feed in late summer-autumn. Leaving the feed standing over summer shades the soil, reducing the evaporative concentration of salts at the surface soil.

It is important to get the site selection right, because while puccinellia can grow on sites without waterlogging and relatively high salinity, it is a poor competitor on such sites and will be out competed by other annual or perennial grasses. As such, puccinellia has minimal weed risk, and won’t dominate a sward like tall wheatgrass.

Puccinellia has a small seed and therefore produces a small seedling. This means that early growth (after emergence) is slow and the seedling is a poor competitor against weeds. Seedlings of sea barleygrass (often the dominant species on saltland suited to puccinellia) are much larger and grow more quickly, and if not well controlled, can overwhelm puccinellia. Good weed control is essential prior to sowing and after emergence.

Likely benefits from this saltland solution

Pasture production from relatively non-productive land is the primary benefit from establishing puccinellia based pastures. In the right situations, they can be highly productive and profitable - with appropriate management and fertilizer application, dry matter yields can be high (~10 t/ha) and stocking rates of 6-8 DSE/ha can be supported.

Importantly, there are no known detrimental grazing issues – puccinellia does not accumulate salt in the leaves in the way many other saltland pasture species do, and it has small and non-invasive seeds.

Puccinellia pastures do provide a significant visual improvement for saline land and because they protect the soil surface over summer, they can significantly slow the build up of salts in the surface soil. However, the primary motivation for establishing puccinellia based pastures is their grazing value. 

Saltland Solution 6 – Puccinellia

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Saltland Solution 7 - Vegetatively established grasses

There are a suite of perennial grasses that can only be established vegetatively, but that have exceptionally high tolerance to salinity, waterlogging or both. These grasses need to be ‘planted’ with segments of stolons (surface runners) or rhizomes (underground stems or runners). The important saltland species are marine couch (Sporobolus virginicus), saltwater couch (Paspalum vaginatum) and distichlis (Distichlis spicata). These vegetatively established saltland species are all quite similar in that they are creeping, relatively fine-leafed grasses that spread via rhizomes, stolons or both, so specific identification can be difficult.

Plants are established in this way either because they produce little seed and/or germinate poorly from seed or the desired genotype is a clone and it can only be established from vegetative material. The planting of material from vegetative sources is quite expensive per hectare, making this method most suited to small areas of saltland, or where time is not critical so sparsely spaced plants can be established and encouraged to spread over time and fill in the gaps.

Because of the expense in establishment, these plants tend to be used mostly in horticulture as turf grasses in situations where the soil is saline, or where only saline water is available for irrigation.

Where is this option likely to be best suited

Despite being sub-tropical species, these grasses (especially marine and saltwater couch) are very widespread throughout Australia and therefore must be very adaptable. The most suitable areas to establish these vegetative grasses will be warmer zones, with relatively high rainfall (>500mm) that is either summer dominant or where conditions remain moist over summer. In line with those requirements it is not surprising that marine couch has been the most widely used saltland pasture species in Queensland.

The most common indicator species would be sea barleygrass, cotula, curly rye grass and perhaps samphire in the most waterlogged and saline situations.

Field observations in NSW have shown that both marine couch and saltwater couch can survive with exceptionally high surface (0-10 cm) soil salinities (40-100 dS/m).

While these grass species all have high levels of tolerance for salinity and waterlogging, there is little information about the field conditions (soil type, salinity down the profile, depth to watertable etc) to which they are best suited – anecdotally it seems that the plants grow well over a range of soil types but establish better and spread faster in sandy soils.

Special features or challenges

Because of the need to establish these species from ‘cuttings’ they are one of the more expensive options for restoration of salt-affected land and little is known about the agronomic management (weed control, fertiliser use etc) of these grasses outside of turf situations.

Actual levels of pasture production from these vegetative grasses have rarely been measured, and while animals will graze these saltland species, performance levels have not been reported.

Likely benefits from this saltland solution

Under the right conditions (warm, moist, and with sufficient salinity to limit competition from other species) these vegetative grasses can provide good groundcover and some grazing in situations that would otherwise be unproductive and/or actively contributing to environmental damaging. Because of the relatively high cost of establishment, it is unlikely that establishing these grasses would be ‘profitable’ in the strict financial sense of the word.

However, the key to most of the amenity and environmental benefits from revegetating saline land is groundcover and these vegetatively established grasses are particularly good at providing it! Green and growing plants on previously bare saline scalds are visually attractive and the groundcover reduces surface soil evaporation and salt build-up, protects the soil from erosion, and provides some basis for re-establishing floral and faunal biodiversity. Their amenity value is confirmed by their extensive use as turf grasses, and the primary motivation behind the use of these grasses is likely to be amenity/environmental rather than production and profit. 

Saltland Solution 7 – Vegetatively established grasses

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Saltland Solution 8 - Temperate perennial grasses with limited salinity tolerance

Limited research reports from as far back as the 1960s have proposed a role for perennial pasture grasses with limited salinity tolerance in the management of waterlogged land with low salinity. Of the established perennial pasture species, perennial ryegrass (Lolium perenne), phalaris (Phalaris aquatica) and tall fescue (Festuca arundinacea) have been used to some extent on land with low salinity.

In non-saline/moderately waterlogged situations, phalaris is generally a more productive, stable and reliable species than the other temperate grasses and it is likely that these same advantages apply on land of low salinity. Tall fescue is the other temperate perennial pasture species with sufficient salinity tolerance to include in this option.

These mildly salt tolerant grasses are rarely used by themselves for saltland rehabilitation – in most cases they are included in a shotgun mix of more and less salt tolerant species. This is because salt affected land is often very patchy and if included in a mix, the temperate perennial grasses will occupy the niches for which they are best suited.

Where is this option likely to be best suited

Phalaris seems to be slightly more salt-tolerant than tall fescue but there is not a big difference – neither will be productive if soil salinity (ECe) exceeds about 6-8 dS/m and both are better suited to soils with salinity levels of the order of 4 dS/m. As a general rule, waterlogging and salinity have additive effects on plant growth, so as the waterlogging at a particular site increases, the salinity levels that phalaris and tall fescue can tolerate will decline.

The ‘classical’ indicator species for saline land (such as sea barleygrass, marine couch or saltwater couch, water buttons etc) all tend to indicate levels of salinity and/or waterlogging that will exceed the tolerance of the temperate grasses - though land suitable for phalaris or tall fescue may be in abundance towards the edges of the saline site and surrounding it.

The suitable range for phalaris is areas receiving more than 300 mm of effective rain between April and October. Tall fescue is less drought-tolerant than phalaris, so in general, better soil moisture conditions are needed – either from better soils, higher rainfall, or higher altitudes where evaporative demand is lower.

As salinity and/or waterlogging at a site increases, the suitability of phalaris and tall fescue quickly diminishes, and tall wheatgrass and puccinellia become more productive and persistent options.

Special features or challenges

Because these perennial grasses can only tolerate sites with low salinity the primary challenge is correctly identifying suitable sites for these species – expensive seed will be wasted if the site is too saline and waterlogged for them to establish and prosper.

There is a very extensive body of knowledge about nearly all aspects of the agronomy, grazing management and animal husbandry associated with phalaris and tall fescue pastures. This makes them a low risk proposition if the salinity of the site is low.

Shotgun mixtures can be positive for the saline site as a whole, but can significantly complicate management because the different species can have different management requirements and grazing needs. In particular the temperate grasses are generally more palatable than more salt-tolerant species and therefore can be eradicated by preferential grazing.

Likely benefits from this saltland solution

Pasture production is the primary motive for using these perennial pasture grasses on saltland. Some visual amenity and landscape protection (erosion control) might be gained, but at these low levels of salinity, the sites will not be bare or scalded unless grazing management is poor or the sites are highly waterlogged. Any system that controls the grazing pressure will quickly lead to revegetation of such sites.

In the absence of salinity, dryland phalaris or tall fescue based pastures can produce >8 t/ha in the higher rainfall, higher altitude areas, and 4-6 t/ha in the medium rainfall, lower altitude zones. With low levels of salinity and waterlogging similar (or even increased) levels of production are possible, but production falls substantially as salinity and waterlogging increases and when ECe values exceed about 8 dS/m, production will be negligible. 

Saltland Solution 8 – Temperate perennial grasses with limited salinity tolerance

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Saltland Solution 9 - Sub-tropical grasses with limited salinity tolerance

Some sub-tropicals are amongst the most salt- and waterlogging-tolerant of the grasses. However, these highly salt- and waterlogging- tolerant species usually need to be planted vegetatively from either segments of stolons (surface stems – runners) or rhizomes (underground stems). The important saltland species in this category are marine couch, saltwater couch and distichlis.

There is another suite of sub-tropical grasses that can be established from seed, and because they are used in non-saline pastures, they have commercial seed supplies. There are now a wide variety of sub-tropical grasses available in Australia, but of these, only 2 species have sufficient salinity and/or waterlogging tolerance to be considered as ‘saltland solutions’. These are kikuyu (Pennisetum clandestinum) and Rhodes grass (Chloris gayana) which are the focus of this ‘saltland solution’ even though local shotgun mixtures often include other sub-tropical species with lower salinity tolerances.

These sub-tropical grasses produce a lower quality forage than the temperate perennial grasses (such as ryegrass, phalaris or fescue) and therefore are only recommended when the temperate species are not suited to the soil or climatic conditions, or if summer growth is a particular requirement. Actual levels of pasture production from these sub-tropical grasses have rarely been measured in saline situations.

Where is this option likely to be best suited

Kikuyu and Rhodes grass are C4 species that require temperatures in excess of 15 degrees Celsius for their photosynthetic pathway to operate. From a salinity management perspective, in effect this means these species are only suited to coastal regions, to the northern agricultural region in WA, and to central and northern NSW.

Both species prefer frost-free climates, though both will survive in frost-prone areas that have summer rainfall.

Kikuyu is highly drought-resistant, but Rhodes grass has only fair tolerance to drought.

Rhodes grass and kikuyu are widely adapted across many soil types but perform best on light to medium textured soils as establishment difficulties have been reported on heavy soils. Soils need to be reasonably well drained for Rhodes grass as it has poor tolerance to waterlogging - kikuyu is more tolerant of waterlogging and acid soils.

Special features or challenges

Because these sub-tropical grasses can only tolerate soils of low salinity, the primary challenge is correctly identifying suitable sites for these species – this may be around the edges of more saline areas, or in the more leached but waterlogged soils of coastal areas.

Because of its creeping habit, kikuyu over time tends to dominate mixed swards and if often sown without other grasses because of this. Rhodes grass is more suited to mixed grass swards.

Where these sub-tropical grasses with low salt tolerance can be used on and around saltland, they have the great advantage of producing green feed over summer, a commodity that is often rare on the rest of the farm.

Both species have a strong ability to spread vegetatively and thicken up even if initial establishment is patchy.

With kikuyu, the key to productivity is to maintain some annual legume in the stand. This can only be achieved if the grasses are grazed exceptionally hard in the autumn to allow legumes to come through in the winter.

Likely benefits from this saltland solution

As with the temperate grasses with limited salinity tolerance, these sub-tropical species are included in shotgun mixtures primarily because they produce useful forage for grazing animals. Sites with the low levels of salinity and waterlogging tolerated by these sub-tropical grasses will be fully vegetated unless overgrazed, and so any management that prevents that overgrazing will allow the site to naturally revegetate.

If sown as part of a shotgun mixture with more salt- tolerant species, these sub-tropical grasses with low salinity tolerance will occupy the least saline areas with no to low waterlogging (Rhodes grass) or moderate to high waterlogging (kikuyu). This can be positive for the saline site as a whole, but can significantly complicate management – for example, good kikuyu management includes episodes of very hard grazing that would lead to most other perennial grasses being grazed out.

The sub-tropical grasses are not salt accumulators and therefore will be nutritionally similar on non-saline land and land affected by low salinity. 

Saltland Solution 9 – Sub-tropical grasses with limited salinity tolerance

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Saltland Solution 10 - Legumes for saltland

Clovers and medics underpin most Australian improved pastures on non-saline land, not only for their significant contribution to animal nutrition, but also on account of the nitrogen they are able to fix from the atmosphere which later becomes available to grasses. The development of a robust salt-tolerant legume is something of a holy grail for graziers with saltland and for researchers.

However, legumes are less salt-tolerant than grasses, apparently due to their relative inability to prevent the uptake of the toxic salts. As a general guide, the most common legume species for saltland are (ranked from most to least salt tolerant) burr medic, lucerne, strawberry clover and balansa clover. However this ranking is only meaningful when set alongside waterlogging tolerance, which will often eliminate lucerne and burr medic from the choices. Melilotus species, which have higher levels of salt and waterlogging tolerance, are presently limited by the lack of available salt tolerant symbiotic rhizobia.

If legumes were available for a wide range of saline/waterlogged situations, then the economics of saltland pastures would receive a considerable boost. This boost would come from a combination of the direct contribution that legumes can make to improved performance from grazing animals, and the indirect contribution that legumes make (via fixed nitrogen) to the growth and feed value of the grasses in the pasture mix.

Where is this option likely to be best suited

Because the legumes have only low tolerance to salinity, there are unlikely to be any situations where legumes alone are sown on saltland. Lucerne is widely used in salinity management across southern Australia to reduce recharge, and is often sown around saltland to reduce local upward pressure from the watertable and thereby reduce discharge onto the saline site. However it is not well suited to saltland itself, tolerating (at best) soils of moderate salinity (ECe values of 4-8 dS/m) and low waterlogging (average watertables deeper than 0.3 m in winter).

Therefore, in almost all saltland pasture situations, the critical productive component will be the salt- tolerant grass or shrub, and the key decisions will relate to which grass, shrub or mixture is the most appropriate for the particular saltland site. Legumes are often included in the seeding mix in the hope that the levels of salinity and waterlogging in parts of the saltland area will be low enough to allow the legumes to establish and make a significant contribution to pasture quality and/or soil nitrogen.

Special features or challenges

The most significant challenge for ‘salt-tolerant’ legumes is that they are not very salt-tolerant, and the combination of tolerances to salinity and waterlogging (conditions common on saltland) is rare.

The gap between current reality and the ‘exciting future prospects’ for legumes on saltland is considerable. Firstly, legumes as a group tend to be much less salt-tolerant than grasses. Secondly, for legumes to achieve their potential they must ‘fix’ nitrogen, which means that not only does the legume need to be able to tolerate salinity, but a salt-tolerant rhizobium is also needed, Finally, a ‘salt-tolerant’ symbiotic relationship between the legume and the rhizobium must be able to form in the hostile environment of a saline soil. These three quite significant challenges need to be overcome simultaneously, and so far they have largely failed to succeed.

Likely benefits from this saltland solution

Legumes are included in saltland pasture mixtures for purely production reasons – they are unlikely to add significantly to the visual amenity or environmental goals that farmers often take into account when deciding to revegetate saltland. On non-saline sites, legumes provide excellent nutrition for grazing animals – the same nutritional excellence can be expected from legumes growing on land affected by low salinity as on non-saline land because legumes do not accumulate salt. 

Saltland Solution 10 – Legumes for saltland

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Saltland Solution 11 - Revegetation with non-grazing species

There are non-grazing options for the full range of saltland sites were revegetation is possible. Saltland Solution 1 – Fence and exclude from grazing is a special case, recommended for sites that that are too saline, waterlogged and/or inundated for other solutions to succeed, to naturally regenerate.
Saltland Solution 11 – Revegetation with non-grazing species is recommended for a much wider suite of saltland sites where grazing may be a suitable land use, but other considerations lead to a rehabilitation plan that includes trees or other non-grazing species as a major component of the revegetation mix. Occasional grazing may be part of this solution, but only at times and at grazing pressures that do not threaten the other benefits being sought – such as establishment of the plants concerned, erosion control, timber production, biodiversity or visual amenity.

There are two different strategies, depending on the farmer’s objectives:

  1. Revegetation with trees and/or shrubs and/or under-storey, but with the selection of revegetation species focussed on conservation and visual amenity, with no aspirations for a commercial product. This strategy is probably the most reliable, because it involves a range of species, and because commercial growth rates are not expected;
     
  2. Revegetation with trees, with the species selected for commercial wood products (saw logs, wood pulp or firewood) rather than conservation or visual amenity. This strategy is much more challenging because a more limited range of species can be planted, the time to achieving a benefit will be long, and both the biology and the marketing aspects have to align if a profit can be expected.

The current interest in planting trees for greenhouse gas abatement may add significantly to the motivation for this saltland option. Carbon sequestration could be particularly attractive for saltland which apart from grazing, has few other prospects for productive use. The commercial settings for C-sequestration could change substantially in Australia over the next few years.

Where is this option likely to be best suited

Successful agroforestry and farm forestry enterprises are most commonly found where annual average rainfall exceeds 600 mm and where processing or port facilities are close by. However, trees grown on saltland often have the advantage of access to a shallow, albeit salty, watertable which can make forestry possible in rainfall zones lower than 600 mm. The limiting factor then is more likely to be levels of soil salinity and waterlogging rather than the availability of soil moisture.

The current suite of commercially productive trees are not highly salt-tolerant but it is difficult to specify exact salinity levels (or even at what depth salinity should be measured) because tree root systems can be much deeper than saltland pastures. The overall conclusion is that there are many risks and challenges associated with commercial tree operations on saltland, and there are no measurements that can be made that will guarantee success over the long time frames associated with commercial forestry.

If visual amenity and conservation are the primary motivations behind revegetating with non-grazing species, then a much higher ‘success’ rate is likely and this option can be used on virtually any category of saltland by varying the revegetation species. A greater mix of species can be used, including non-commercial trees and shrubs, some of which have significantly higher salinity and waterlogging tolerance. Actual growth rates are much less important as harvesting is not part of the plan, and little is lost if some species die out either initially or over time.

Special features or challenges

Most of the risks associated with revegetation of saltland with trees are more applicable to commercial options than to conservation plantings. The main risks associated with commercial forestry on saltland are:

  • Tree growth rates will be slowed by salinity and waterlogging to levels that cannot provide a commercial return;
     
  • Saltland sites are often smaller than required for commercial forestry operations, and are often located at challenging distances from markets;
     
  • Sites that are currently suited to forestry may become more saline and waterlogged (and therefore unsuitable) over the long time span needed for forestry options to mature; and
     
  • The water use by the trees results in significant salt accumulation in the root zone, perhaps rendering this option unsustainable in the long-term.

Some of these challenges also apply if carbon credits are sold from trees planted on saltland. The rules associated with planting trees for carbon credits need to be very clear before this option could be recommended.

Likely benefits from this saltland solution

While commercial benefits are theoretically possible either from plantation forestry or from selling carbon credits, neither of these look like safe prospects in the near future. Commercial tree planting and carbon sequestration are both long term ventures, probably best focussed on land that does not have the potential to change and become more hostile to tree growth and survival.

By far the most likely benefit from this option is visual amenity. Farmers involved in revegetating saltland are highly motivated to see the visual improvement that revegetation can provide, and if non-grazing species are used, biodiversity benefits can also be expected. 

Saltland Solution 11 – Revegetation with non-grazing species

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