Oldman saltbush, and probably most other relatives, have their greatest potential where there is a well-defined autumn feed gap and the property has a significant amount of scalded land that does not grow good pasture any more.
It is very expensive to establish but is very hardy once a few years old. Its role is as a drought reserve or a special purpose crop, not a production system.
Oldman saltbush grows well only on heavy clays and alkaline clay-loams. Saltbushes are not suited to the tropics or coastal and cool upland areas.
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Saltbushes are members of a worldwide family of plants (Chenopodiaceae - chenopods) that are common in deserts and salty environments. They vary in size from small fleshy herbs to large woody shrubs. In many rangelands they constitute the dominant shrubby vegetation and are also the staple diet of many animals.
Saltbush (Atriplex species) and bluebush (Maireana spp.) are closely related subgroups and there are about 60 species of each in Australia. There are another 30 to 40 related chenopod species that have similar forage value and appearance. Some are annuals but many are strongly perennial.
One of the best-regarded saltbushes in the world is Australia´s oldman saltbush (Atriplex nummularia). This tall shrub was very common in the Murray-Darling Basin in the 19th century but has now disappeared from many areas.
Currently the wool industry in the rangelands of western New South Wales (NSW), South Australia and Western Australia depends on saltbushes and bluebushes for its survival. Many of the saltbushes are palatable, nutritious and tolerant of drought, frost and saline soil. Hence people are often tempted to try to sow and grow them commercially. In practice, this is not easily done and only a few species lend themselves to classic agronomic practices. Only oldman saltbush has been commercialised to date in eastern Australia but many others have been tried. Two species native to Western Australia, river saltbush (A. amnicola) and wavy-leaf saltbush (A. undulata), have been widely tested but they have not done well in southern Queensland.
In the United States the native fourwing saltbush (A. canescens) has been grown commercially, and Mediterranean saltbush (A. halimus) is used a little in the Middle East. Many species would make good low maintenance, slow-growing ornamentals for arid zone gardens and parks.
Shrubby saltbushes are generally rich in protein, minerals and salt but are not highly palatable. They are relatively slow growing, quite woody and do not refoliate rapidly after grazing, except under good autumn and spring conditions. Hence they must be well established (over 18 months old generally) before they can be grazed. Thereafter they can only be grazed intermittently, once or twice a year for short periods.
Some have high levels of oxalates in the leaves and this can be toxic to hungry stock if eaten in excess. Fortunately, oldman saltbush is not recorded as being poisonous but there is also no evidence of it contributing to weight gain in stock - it just holds them in their current condition.
The most common shrubby saltbushes are strongly perennial and will live for decades. Though tolerant of saline sub-soils some are quite sensitive to other soil characteristics. It is believed that oldman saltbush is intolerant of free aluminium ions and so will not persist in very acidic conditions, such as on mulga soils.
Oldman saltbush is well adapted to heavy alkaline clay soils and in western NSW sown stands of it also persist well on texture contrast soils, especially on slightly higher levees of river frontages.
Mediterranean saltbush is suited to sandy loams but dies on Australian clay soils. Likewise, river saltbush from Western Australia does not persist on heavy alkaline clays. Fourwing saltbush is tolerant of a fairly wide range of soils and mine spoils. A number of species will grow and persist on saline mine spoils in the absence of grazing.
Experience over the last 25 years shows that shrubby saltbushes are well adapted to dry arid atmospheres. Under such conditions they have no significant pests or diseases. Stem borers sometimes damage plants and red-legged earthmite is suspected of causing problems to some saltbushes in southern Australia. Higher rainfall environments, especially where summers are wet or winters are persistently damp, do not suit these plants.
All the perennial species are difficult to establish from seed and therefore are usually sown as transplants. This overcomes the need to leach salts from the seed coverings before sowing and the slow, weak seedling growth rate.
Unfortunately, the cost of establishing a stand then becomes very high because of the need to water the seedlings initially and to control weeds. Costs range up to $800 per hectare for 2500 to 3000 bushes. On top of this, most have separate male and female plants and must cross-pollinate. Therefore isolated plants can never spread or thicken up without an opposite-sexed plant nearby.
Sowing saltbush should only be considered in Queensland and northern NSW under the following two situations:
- where soil salinity or structure precludes most other plants from surviving
- where a very specific feed gap occurs every year that saltbush leaf protein can fill.
In the first instance, the land has little potential for growing grass or salt-sensitive trees and the cost of establishing saltbush is justified by the long term, although low level, production achieved. Only on claypans in arid inland Australia and on very saline land elsewhere are these conditions likely to be found. Saline soil or water will significantly slow even saltbush growth and seedlings will not establish quickly in soils with very saline surface conditions.
The second situation is more likely to be a feasible commercial proposition and it depends on the consistent shortfall of quality feed such as is experienced in semi-arid southern Australia in late summer.
However, there could also be a role at other times where grazing a reserved saltbush area allows spelling of another part of the property. Each saltbush paddock responds best if grazed fairly intensively for only a short time. If grazed for too long, animals damage regrowing twigs or start to trample bushes in their search for protected, less accessible leaf.
Commercial companies that sell saltbush offer plenty of good advice about sowing and grazing shrubby saltbush such as de Koch saltbush. This is actually a line of oldman saltbush that was selected in South Africa from material that was originally native to Australia. Comparisons show that it is virtually indistinguishable from remnants of oldman saltbush growing in southern Queensland.
Fortunately, red and grey kangaroos do not particularly like saltbushes so they won´t damage new sowings. The situation with wallabies, hares and rabbits is not clear but there is no knowledge of problems with rabbits or hares. Transplants are normally planted about 1 metre apart in rows spaced 2-3 metres wide. Inter-row space is determined by rainfall zone and by the width of tillage implements used to control weeds.
Sowing is best done in cooler weather for several reasons, including:
- reduced demand for irrigation water
- plants are less stressed
- grasshoppers and insects are less active.
Seedlings grow slowly in mid-winter but well-rooted ones grow well in the next spring and early summer. On clay soils, de Koch variety needs no fertiliser but weeds must be controlled in the first year. In later years, grasses should be encouraged to grow in the interrows to provide a balance in the diet available to the livestock and to protect the surface soil. The saltbushes are very competitive and grasses do not grow well beneath their canopy.
A well-grown oldman saltbush plant grows over two metres tall and eventually, if ungrazed, will sprawl 4-5 metres wide. However, under annual grazing most bushes are only 1-2 metres across and 1.5 metres tall. Large stands have been successfully established at Hannaford, St George, Cunnamulla and Narromine.
Typical grazing systems run about 125 adult sheep (50 sheep/acre) or 15 steers/ha. At this rate 4-6 weeks grazing is possible and then the paddock must be rested for at least 8 months. Without favourable seasonal conditions during this spell, grazing must be delayed until the bushes have fully refoliated. Thickening up or spread by seedlings is virtually impossible under this grazing system.
Oldman saltbush subjected to open grazing was exterminated from large areas of Australia in the late 19th century. Nonetheless, its low palatability means new stock usually take a few days before seriously grazing saltbush, although drought-hungry stock usually take to it with some relish.
Nutritionally, saltbush has quite high protein and moderate digestibility, akin to rangeland legumes and better than mature green grass. However it is high in salt and stock need to be on good quality water to allow a high intake level.
Despite the reasonable chemical quality of saltbush it does not produce significant weight gain on its own. Feeding grain with saltbush can produce some weight gain. Actual weight gains and wool growth depend on the saltbush species and the circumstances of the animals, such as age, condition and stocking rate.
However, oldman saltbush is usually more nutritious than other species grown commercially in Australia. Carcasses of animals from saltbush are reported to have surprisingly low fat cover for the quality of the meat and the conformation of the animal.
- Glenn E, Tanner R, Miyamoto S, Fitzsimmons K & Boyer J 1998, Water use, productivity and forage quality of the halophyte Atriplex nummularia grown on saline waste water in a desert environment. Journal of Arid Environments 38: 45-62.
- Cunningham GM, Mulham WE, Milthorpe PL & Leigh JH 1981, Plants of Western New South Wales. NSW Soil Conservation Service, Sydney.
- Malcolm CV & Allen RJ 1981, The Mallen niche seeder for plant establishment on difficult sites. Australian Rangeland Journal 3: 106-109.
- Norman H & Filmer M 2008, Make the most of saltbush forage. Farming Ahead No. 193., viewed February 2011, www.csiro.au/files/files/piqt.pdf.
- Saltland Genie 2009, Establishment & management of dense saltbush plantings, viewed February 2011, http://www.saltlandgenie.org.au/solutions/ss3-saltbush/establishment-and-management-of-dense-saltbush-plantings.htm.
- Warren B, Casson T & Barrett-Lennard E 1995. Value of saltbush questioned. J. Agric. W.A. 36: 24-27.