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SOLUTION 4

Saltbush & under-storey

 

4.1  Saltbush & under-storey in a nutshell

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A quick summary

Much of the original published information about saltbush focussed on dense saltbush plantings – as detailed in Saltland Solution 3 – Dense saltbush plantings. Typically, dense saltbush plantings would have at least 1000 saltbush stems per hectare presenting a significant challenge for vehicle access and livestock mustering. 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). Dense saltbush plantings are now only recommended for saltland sites with high summer salinity (subsoil ECe values of 8-16dS/m).

Over time it has become clear that where an annual under-storey between the saltbush rows is possible, the under-storey provides the bulk of the feed for grazing animals. In this Saltland Solution saltbush is usually sown in multiple rows, with a wider alley between the sets of rows for the under-storey. This makes it a cheaper option as well as allowing easy vehicle access and livestock management. In this configuration, saltbush may have 500-600 stems per hectare but this can vary widely depending on the width of the alley ways. Old man saltbush and river saltbush are the best species for this system. Old man saltbush has the advantages of supporting slightly better animal performance and of not spreading across into the inter-row. River saltbush though tends to be more tolerant of transient waterlogging.

Saltbush & annual under-storey species is now the option most recommended for low rainfall 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. Saltbush with a perennial species under-storey such as puccinellia, tall wheatgrass, Rhodes grass and lucerne, is an option for higher rainfall areas. The persistence of these perennials depends on the soil salinity and the effectiveness of the saltbush drawing down the groundwater levels over time.

Saltbush in the saltbush & under-storey 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. If saltbush can draw down the watertable even slightly (for example 20-30cm), this can make a substantial difference to the surface soil conditions and the ability of a site to support a more productive and higher value under-storey.
     
  2. Providing some green feed in autumn, at a time when most farms in the rainfall zone suited to this option will have only dry standing feed. It has been estimated that green feed in autumn in the WA wheatbelt has a value 10 times that of the same feed in spring

The saltbush used in this option are mainly old man and river saltbush (Australian natives), and sometimes wavy leaf saltbush (introduced from Argentina). These are established as either seedlings (lower risk but higher cost) or by direct-seeding (higher risk but lower cost).

The under-storey in the saltbush & under-storey system also has two key roles:

  1. The primary role is to provide feed for livestock in as greater quantity and of the best nutritive value possible;
     
  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 under-storey species used in this option will grow best at low summer soil salinities (subsoil ECe values of 2-4dS/m) but may tolerate moderate summer salinity levels (subsoil ECe values of 4-8dS/m). A mixture of improved species is usually the best option, involving (depending on location, rainfall, etc.) annual legumes (such as balansa clover, sub-clover, burr medic) and grasses (such as annual ryegrass). At high summer salinity levels (subsoil ECe values of 8-16 dS/m)  dense saltbush plantings become the recommended option where puccinellia, tall wheatgrass and annual ryegrass cannot be established. Simply allowing an under-storey of volunteer species is also an option but the under-storey will tend to be dominated by sea barleygrass.

The profitability of the saltbush and under-storey system can be substantially higher than for dense saltbush plantings because of the lower establishment cost and higher carrying capacity.

As with dense saltbush, the option is suited to sites with little waterlogging – many of the possible under-storey species are quite tolerant of waterlogging, but in such conditions, the saltbush will not thrive and may not even survive. Where waterlogging is likely, the salt tolerant grasses are likely to be a better option. For more information, see Saltland Solution 5 – Tall wheatgrass, Saltland Solution 6 – Puccinellia, and Saltland Solution 7 – Vegetative grasses.

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History

Historically, saltbush country has been held in high esteem by pastoralists in the drier regions of southern Australia – especially for grazing sheep. Most of the native saltbush country was not saline, however, saltbush accumulates salt in its leaves, and it can be highly tolerant of salinity.

The history behind saltbush itself has been outlined in Saltland Solution 3 – Dense saltbush plantings, but in summary:

  • The late Clive Malcolm pioneered saltbush for saltland work in WA from 1954 to 2006.
     
  • The combined benefit of saltbush and low quality roughage was demonstrated in several feeding trials – for example sheep fed a 1:1 mixture of poor quality hay and saltbush, ate 1.5 kg of dry matter per day, and gained 70 grams a day. The sheep fed hay alone (voluntary intake 0.9 kg of dry matter per day) or saltbush alone (intake of 0.7 kg of dry matter per day) lost 25 and 225 g/day respectively.
     
  • However, research from the early 1990s greatly undermined confidence in saltbush by showing that its nutritive value was poor, so that sheep fed saltbush gained water but lost weight.
     
  • By the late 1990s, wool and lamb prices were improving, and farmer experience with saltbush and other saltland pastures were proving much more positive than indicated by research. This re-ignited interest in saltbush-based saltland pastures.
     
  • The Saltland Pastures Association (SPA) was formed in 1997, and Michael Lloyd (Chair of the SPA) became a leading farmer advocate for saltbush in particular and saltland pastures in general. Researchers came to realise that even in dense saltbush plantings, the under-storey was a major source of feed for livestock. In one experiment, where the site was selected to minimise sheep access to under-storey, it still contributed 45% of the feed on offer. In a paper to the 1998 PUR$L conference, Ed Barrett-Lennard and Mike Ewing said “In our vision of the new model of saltland pasture, the components of the system would have different roles. The perennial species would be mainly responsible for the transpiration of groundwater, the lowering of water tables and the reduction of surface soil salinity. They would also decrease wind and water erosion. This would enable better growth of annuals. The annual species would be mainly responsible for production of fodder and the generation of farm income.”

The development of saltbush alley farming systems with annual pasture under-storey followed, and is now the most widely recommended saltland pasture system for the lower rainfall areas. Saltbush with perennial under-storey  such as tall wheatgrass, puccinellia, subtropical grasses and lucerne are becoming important grazing systems in higher rainfall areas.

The SGSL (Sustainable Grazing on Saline Lands) initiative of Australian Wool Innovations and Land and Water Australia, and the CRC Salinity focused more strongly on improving the performance of the under-storey than on saltbush.

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Species identification

SALTdeck was produced by the SGSL initiative to assist with the identification of the 50 most common saltland species. These can be viewed individually on this website or they ordered from the Saltland Genie

The saltbush species have been described in some detail in Saltland Solution 3 – Dense saltbush plantings but the SALTdeck cards can be viewed below:

Figure 4.1 – SALTdeck identification card for old man saltbush 

Figure 4.2 – SALTdeck identification card for river saltbush 

Figure 4.3 – SALTdeck identification card for wavy leaf saltbush 

Figure 4.4 – SALTdeck identification card for creeping saltbush


Recommendations for what should be included in a sown under-storey are not so clear. Across the SGSL grower network sites, almost all saltland species were trialled, including most of the perennial grasses (puccinellia, tall wheatgrass, sub-tropical grasses and temperate perennial grasses). From this experience we conclude:

  • If the site is suitable for saltbush, then puccinellia will grow in highly saline sites in rainfall areas > 350 mm.
     
  • If the site is suitable for tall wheatgrass, then tall wheatgrass can contribute high production and nutrition ( if not rank) to the saltbush stand.
     
  • If the site is suitable for either the temperate or sub-tropical grasses with limited salinity tolerance then they are probably a better perennial option than saltbush.
     
  • The annual pasture species (legumes and grasses) are probably the best under-storey option for saltbush pastures in the 300 to 450mm rainfall zone. They can take advantage of the improved environment created by the saltbush but do not compete for moisture over summer.
  • The perennial pasture species should be considered in areas with > 350 mm rainfall.

            

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 as shown from the SALTdeck cards below. 

 Figure 4.5 – SALTdeck identification card for balansa clover 

Figure 4.6 – SALTdeck identification card for burr medic 

Figure 4.7 – SALTdeck identification card for barrel medic 

Figure 4.8 – SALTdeck identification card for annual ryegrass 

Figure 4.9 – SALTdeck identification card for Italian ryegrass

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