Old man saltbush (Atriplex nummularia) is a well-known sight in South Africa and this hardy plant with its ability to tolerate high salinity and drought is especially common in areas with lower rainfall and where small stock is farmed extensively.
Grootfontein College of Agriculture used to import saltbush from Australia, which has 60 different species. They conducted in-depth research into the differences in palatability and remarkable characteristics of the plant, resulting in an upsurge in this perennial dryland and summer grazing crop’s popularity, especially during the 1970s and 80s.
Is old man saltbush still considered a popular source of nutrition today? And is there a future for the plant in South Africa where is has been classified as a Category 2 invader, therefore requiring a permit to cultivate and plant it under controlled conditions?
A versatile plant
Saltbush has two uses, according to Dr Aart-Jan Verschoor, senior manager of Strategic Information Management at the Agricultural Research Council (ARC).
The first is that a saltbush fodder bank can help animals survive if, during drought, you need something to carry them through. The other is that as a feed source, saltbush has relatively good nutritional value and can be combined with supplements such as maize to boost animals’ condition for marketing.
“Saltbush is generally not very palatable, and it takes sheep two to three days to get used to it,” says Dr Verschoor. The leaves are covered in hair, or trichomes, which collect and store salt and sometimes burst open to release these salts. “The leaves contain between 70 and 80% water, which means animals are able to better utilise other dry plant material. Apart from a well-developed root system, that is just one of the reasons why it performs so well as livestock feed and reserve crop during times of drought.”
These halophytes (salt-tolerant plants) remain green and lush, even in drought conditions. They can adapt to most climatic and soil conditions, including frost and cold, which the Karoo is known for. Dr Verschoor adds that it is a dioecious plant (male and female plants are separate). “The plants are efficient water users and can get by with very little. They also produce relatively high yields in adverse conditions. A key feature is their ability to thrive in brackish soil that is in disuse due to excessive irrigation.”
Establishment and management
Although saltbush is still being used as livestock and reserve feed, the number of plantings has decreased over the years.
According to Dr Paul Malan of the Department of Animal, Wildlife and Grassland Sciences at the University of the Free State, the time-consuming nature of the seed germination process and the difficulty in establishing the saltbush may be the main reasons for this. “The plants only grow in spring and autumn and it takes a while before the replanted seedlings can be grazed,” he says.
Dr Verschoor agrees that seedling establishment must be managed with care. It usually takes a year for a seedling to develop into a grazable shrub. He says the shrub can be utilised from eight months onwards, but preferably only after a year of good growth.
The process from seeds to grazable plants entails the following:
- The seeds are rinsed to remove inhibiting substances. The rinse water must be replaced twice a day for two to three days.
- Seeds should preferably germinate in seed trays or bags or in moist, covered soil.
- Seedlings 20cm in length with a woody stem are replanted, initially irrigated and good weed control applied. Between 2 500 to 3 000 plants are planted per hectare.
- Irrigation should be applied a few times during the first year after establishment in order to accelerate plant development.
- Saltbush must be pruned annually or biennially; this way, lush shoots stay within reach of livestock. This also prevents older, harder saltbush twigs from damaging cutting equipment.
Nutrition and grazing capacity
Saltbush has excellent carrying capacity and research shows that two to 15 small-stock units/ha/year can be kept on saltbush. According to Grootfontein College of Agriculture’s studies, this amounts to around 21 sheep/ha for four months at a plant density of 2 500 plants/ha.
As saltbush is not particularly palatable, a relatively high grazing pressure is recommended. “Apart from high grazing capacity, the shrub’s ability to recover after intensive grazing is good. This means that plants can be utilised quite heavily every year without it having a detrimental effect on their growth potential. If saltbush is extensively grazed each growing season, a resting period of between six and eight months is recommended for adequate recovery,” says Dr Verschoor.
Saltbush is high in sodium and potassium and has a dry matter (DM) production figure of between 2 and 4,76 tons DM/ha. It is also high in highly digestible crude protein (12 to 24%). Energy-rich supplements such as maize, hay or lucerne are often added to saltbush since the crude protein is quickly converted to volatile ammonia, which is not readily absorbed in the digestive track, in the sheep’s rumen – energy-rich supplements counteract this process.
The ostrich industry is a good example of optimal saltbush utilisation. Klein Karoo producers supplement the saltbush feed bank with lucerne hay, molasses or maize to finish their ostriches. “That is why I believe saltbush has a place in feed rations,” says Dr Verschoor, “especially since our weather patterns seems to be changing.”
Benefits of old man saltbush
- In South Africa, times of abundant grazing are typically followed by times of scarcity – periodic droughts are common – and the plant can assist in bridging this challenge.
- Most fodder crops struggle in drier areas, especially where irrigation water is scarce. Saltbush can survive with little water.
- Drought-resistant saltbush can buffer drought damage and feed scarcity.
- It is ideal for strategic withdrawal of veld and is suitable as a fodder bank to relieve pressure on veld.
- In winter rainfall regions, autumn utilisation is ideal for improving animal performance, especially when combined with energy supplements.
- Saltbush is mostly regarded as maintenance feed. It is low in energy, but can be supplemented with lucerne hay, maize or molasses.
- It is a low-cost, high-quality alternative delivering the best performance when combined with an energy supplement.
- It is a good source of maintenance roughage, even for pregnant ewes, when combined with energy supplementation.
- Saltbush meal can replace up to 30% of lucerne in ostrich rations. Given the fact that nutrition accounts for 60 to 70% of an ostrich farming enterprise’s costs, using saltbush is much cheaper and it can easily adapt to poor soil.
- Saltbush is a typical supplementary, protein-rich crop containing a variety of nutrients (micro-elements).
- Oudtshoorn-based producers probably only have water for 60% of their irrigable land in the long term and it may turn brackish – in these cases saltbush can serve as a possible alternative to lucerne.
At a rate of 2 to 3kg per SSU/week, old man saltbush is a cheap natural rumen stimulant when cut as greenfeed and spread out in the veld, while the herd’s hoof action also has a good impact on the veld. –Carin Venter, Stockfarm