Saltbush a valuable supplement for marginal land

Key points:

  • Saltbush can help fill the autumn feedgap, treat mineral deficiencies and provide shade and shelter.
  • Saltbush can grow in a variety of climates and soil types but is typically not suited to waterlogged areas.
  • Both sheep and cattle can benefit from saltbush.
  • Saltbush shouldn’t be constantly grazed.
  • While saltbush has reasonable energy, low fibre and is a valuable source of protein, the salt and sulfur content means it will only fill one-third of an animals diet, so an understorey needs to be considered.
  • Golden rules and upcoming events in Jerramungup and Elgin are provided below.

Dr Hayley Norman with Chatfields Tree Nursery owner Dustin McCreery.

Livestock producers seeking a better return from marginal land could consider supplementing their pasture with old man saltbush (Atriplex nummularia), according to CSIRO researcher Dr Hayley Norman who has been studying saltbush for more than twenty years.

“Saltbush does not need salt to grow. So, where land is marginal for other reasons, such as rocky areas or infertile sandy soils, shrubs can still be a valuable supplement,” Dr Norman said.

“Farmers need to consider the opportunity cost of what else they could do with that land, but if they’re trying to fill a feed gap and they’re seeing nutrient deficiencies through summer and autumn, I think shrubs offer great value. Shrubs provide a whole range of minerals, particularly vitamin E, and are a source of protein. As well as reducing supplementary feed costs, shrubs can also provide shade in summer and shelter during lambing.

While old man saltbush is usually associated with low to medium rainfall areas, Dr Norman said it grows quite happily in the high rainfall zone, as long as it doesn’t get waterlogged.

“River saltbush (Atriplex amnicola) is about the only forage shrub that will tolerate waterlogging.”

There’s also no difference between sheep and cattle in terms of how much saltbush they will select in their diet if given a choice.

“In one study we did, merino sheep and cattle both chose 35% salt bush in their diet. While sheep are known to have greater salt tolerance than cattle, if there is plenty of fresh water, cattle perform well. The shrubs would probably prefer cattle because they’re less likely to strip off every last leaf. However, you need to be careful grazing establishing shrubs for the first time with cattle because they are more likely to pull them out of the ground”.

While saltbush is very hardy and, if rested, will come back after being grazed down to bare sticks, shrubs are unlikely to do well if constantly grazed. This means the timing of grazing needs to be considered.

“In the central wheatbelt, farmers will tend to put sheep into saltbush paddocks when crop stubbles are finished in late summer, and often leave the sheep in those paddocks while they undertake intensive feeding to allow winter pastures to establish.

“Access to shrubs while stock are on crop stubbles or dry pasture helps increase levels of vitamin E (an antioxidant) and key minerals associated with antioxidant pathways (sulphur, copper, zinc, selenium and manganese). So, in summer you could set animals up to have antioxidant pathways working, improving health, meat quality and perhaps reproductive capacity. Letting the animals into shrubs every month for a bit of a top up may be a good way to go about it”.

How quickly stock graze shrubs after being brought into the paddock depends on whether they recognise it as food.

“If you just put naive weaner sheep into a saltbush paddock, they don’t recognise it as food and it will take about two to three weeks for them to learn to eat it and top up vitamin E levels.  Ewes more familiar with the feed would take less time. Also, if it’s a relatively palatable variety such as AnamekaTM (Atriplex nummularia cv Anameka), the animals will eat it more quickly so need even less time”

Hogget with old man saltbush

Of course, it’s not always ideal to eat all the shrubs, especially if part of the aim is to provide shade or shelter. So deferring grazing until the time shelter is no longer needed, or having less palatable species in the mix, may be beneficial.

Rhagodia preissii is a relative of saltbush and has high energy value but is very high in saponins and stock often won’t eat it, so it could be a good option for shelter. It’s a nice dense shrub and it loves sandy soils. We are currently developing a research project to investigate some of these issues with WA producers and colleagues from Murdoch University, the University of WA and the NSW Department of Primary Industries.”

The critical aspect of using shrubs is that there needs to be an understorey, because shrubs will only make up about one-third of the animal’s diet. This is why they are often planted in alleys or blocked onto the poorest parts of the paddock to allow easy access for re-seeding of the understorey.

“The understorey is a really important part of the productivity. Saltbush is up around 20% crude protein, but some of that is non-protein nitrogen, so animals will only use it to make protein if there’s sufficient energy available to them. If they just ate shrubs and didn’t have any additional energy, they would probably just urinate out some of that nitrogen.

“Anameka saltbush is 64% organic matter digestibility, so it has reasonable energy and low fibre, but there’s definitely excess nitrogen to energy, and the same goes for sulfur. Sulfur levels tend to be really high, which is great for wool production, but if they just ate saltbushes, they’d either eat too much salt or too much sulfur, and they’d tend to stop before they met their nutritional requirements. So saltbush is only one-third of the diet. It’s better to think of it as a high value supplement within the diet.”

In the lower rainfall zone, saltbush is typically planted at no more than 700 plants per hectare. This could be increased in the high rainfall zone, especially if excess groundwater exists, but any more than 1200 plants typically results in plants competing for water. Likewise, trees will compete for water so it can be hard to establish mixed stands.

Dr Norman encouraged farmers to consider what the critical limitation is in their farming system.

“What do you supplementary feed, how are you providing it and how else could you achieve that goal. I wouldn’t be putting shrubs into my best cropping or forage country.  At the same time, if you’re going to spend money on AnamekaTM, which is more expensive than a standard saltbush because it has to be vegetatively propagated, I would put it in the better marginal country and see the value for it. It’s heartbreaking to see somebody put Anameka into a waterlogged and highly saline area where it is doomed to fail.”

Dr Norman said that researchers have learnt some golden rules over the past twenty years:

  1. Right plant in the right place. Old man saltbush subspecies nummularia has higher feeding value than the local spathulata subspecies. AnamekaTM has higher feeding value and relative palatability so use it in the better marginal country. Use River saltbush where waterlogging is expected.
  2. Site selection. Choose sites that are not too saline and not waterlogged. In valley floors avoid the samphire zone – start at the edges where you can still grow a crop and work your way in as the land dries out. Saltbush will tolerate sandy soils but performs best where there is some gravel below the sand. Saltbush can thrive on clay soils
  3. Establishment. Plant seedlings deep to keep the root ball as moist as possible during the establishment year (a few leaves visible above ground). Planted in winter, shrubs can be lightly grazed the following summer/autumn as long as animals don’t rip them out and leave one-third of the leaves behind. Watch out for bugs and Kangaroos.
  4. Supplement or complement. Aim to fill one-third of the diet with saltbush leaf and the remainder with something else such as understorey, hay, herbaceous perennials or a good stubble. Sheep and cattle will tend to select feed at these proportions if given a choice. Meet the energy needs of reproducing or growing stock with other supplements.
  5. Drinking Water. Provide unlimited cool non-saline drinking water.
  6. Do they know it’s a feed? Utilise opportunities to train young animals by putting them in with mum or experienced peers. In utero exposure during the last 50 days of pregnancy has shown to be useful (don’t neglect supplementation of the ewe).
  7. Water-table drawdown. If water use is the primary objective, keep plants leafy in summer. Lowering of water tables is most effective on hot days when evapotranspiration is high.

Dr Norman will present at the free “Master Class in Saltland Management for WA” in Jerramungup on the 21st and 22nd of September. See https://www.fbg.org.au/ for more information.

South West Catchments Council (SWCC) is supporting a “Forage Options” event at Bell Pasture Seeds in Elgin on the 8th of October where Chatfield’s Tree Nursery owner Dustin McCreery will speak about using saltbush as a forage. For more information, see the events page on the https://swccnrm.org.au/ website.

 

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