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Unit 1 - What's in it for me?
Unit 2 - Saltland Basics
Unit 3 - Can I trust the technology?
Unit 4 - Plant and animal performance
Unit 5 - Sheep, cattle and conservation
Unit 6 - Do the $$$'s stack up?
Unit 7 - The saltland toolbox
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SOLUTION 1

Fence and exclude from grazing

 

1.4  Level of confidence in fence and exclude from grazing

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How reliable is the information?

There has been very little systematic research into the use of samphire as a land management option, largely because there is no chance of any financial return from investing in samphire on-farm. Consequently, the reliability of the information included in this saltland solution will be considerably less than for well researched options like saltbush or salt-tolerant grasses.

On the other hand, there is quite comprehensive botanical information about the identification and the distribution of various samphire species.

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The main risks and challenges

When a saline site is protected from grazing, samphire will inevitably occupy the most severely affected saltland, given sufficient time. Samphires generally form the first community around the fringes of severely waterlogged salt scalds and saline lakes.

Despite historical advice to the contrary, samphire should not be grazed because the salt (ash) concentrations in the leaves are too high. Research under controlled conditions has shown that both waterlogging and salinity increases the salt content in samphire shoots, increasing from ~14% (under non-saline drained conditions) to >40% (under hypersaline, waterlogged conditions). Field samples collected in WA in 2002 found salt concentrations in samphire at Meckering and Tammin of 20–26% (in winter/spring), increasing to 25–33% (in summer/autumn).

The dynamics of samphire recruitment are poorly understood, though paradoxically samphire seedlings survive best at low salinities. This is probably why natural samphire establishment appears to be episodic, occurring after floods. Seeds are carried in flood water will germinate after the floods recede on soils that have been substantially leached of salt. Given the importance of flooding, samphire recruitment is likely to be highly variable between sites and years.

Farmers wishing to encourage samphire stands may therefore be best advised to harvest the shoots of local plants by hand or with a forage harvester, and spread the harvested material on the ground. Tickling the soil surface with a scarifier can also help create seed niches. See the WA Farmnote by Malcolm and Cooper (1988) for more information about samphire establishment.

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Prospects

This solution to highly saline and waterlogged land is not amenable to improvement in the ways that might be applied to productive saltland pastures. Improved varieties and management techniques are not going to be developed.

During the latter years of the 20th century, dryland salinity expanded quite rapidly across southern Australia, driven by above average rainfall. At this time, the prospect was that more and more land would become suited to this option of fencing and excluding from grazing. However, with the recent run of dry years, expansion of salinity in the lower rainfall areas of Australia has been minimal and it seems the rate of expansion of the land in this salinity class will be slower than in the past. Of course, a return to a series of above average rainfall years would lead to more saline land, including the highly saline and waterlogged land suited to fencing and excluding from grazing.

Despite the current slow expansion of dryland salinity, there is some research underway to better understand the ecology of these highly complex saline/waterlogged ecosystems and provide insights into future prospects for fencing these sites and excluding them from grazing might emerge.

Associate Professor Tim Colmer leads a research group in the School of Plant Biology at the University of WA that is doing the only research on samphire in Australia. In recent years there have been two honours projects and two PhDs completed:

  • Digby Short examined the salt tolerance of Halosarcia pergranulata in nutrient solutions. He found that the plants had optimal growth at ~36% of the salinity of seawater, but were still alive at salinities of 80 dS/m (~145% of seawater). At the highest salinity tested, more than half of the shoot weight was made up of salt accumulated in the leaves, clearly supporting the view that these plants should not be grazed.
     
  • Sarah Rich examined the flooding tolerance of samphire. She found that this species is so well adapted to flooding that aquatic roots contain photosynthesising chlorophyll, and that the activity of this can produce considerable oxygen and sugar for plant use.
     
  • Jeremy English examined the ecophysiology of a range of samphire species at Hannan’s Lake near Kalgoorlie, WA. Halosarcia pergranulata (a species found at the edge of the lake) had an ability to produce adventitious roots that contained aerenchyma, whereas H. indica (a species found on the low dunes bordering the lake) did not form such adventitious roots. Zonation in this genus is likely to be related to differences in waterlogging tolerance of the species.
     
  • Kelly Shepherd examined the taxonomy of this complex genus.

The Colmer group also has a continuing program on the inundation tolerance of samphire in the Yenyenning Lakes system in WA (see Pedersen et al. 2006).

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