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SOLUTION 10

Legumes for saltland

 

10.2 Most likely situations for saltland legumes

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Landscape niche

All plants have landscape niches or zones (combinations of climatic and soil conditions, and management) where they are most competitive or where they will perform best. Saltland plants are the same, each tending to have a particular set of climatic (rainfall, temperature etc) and soil (salinity, waterlogging) factors which determine where they will be able to survive, and where they are likely to thrive. For saltland legumes, these factors are summarised in Figure 10.8. 

Figure 10.8 Most likely situations for saltland legumes.

Subsoil salinity/ depth to watertable matrix

 Winter

Summer 

 

 

Drivers of legume zonation

  • Low salinity tolerance
  • Non-halophytes and very limited salinity tolerance
  • Some are sensitive to waterlogging, others thrive
  • Annuals more promising than perennials
  • Reestablishment of annual legumes an additional challenge
  • Rainfall >300mm

 


Key to symbols

red dot

This is the zone most preferred by saltbush and where it is highly recommended;

Small Dot

Saltbush is one of the possible options for this zone but it is outside its preferred conditions;

 

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Common indicator species

Balansa and strawberry clovers and melilotus species thrive in conditions with winter waterlogging but only moderate levels of salinity. In addition, strawberry clover needs summer moisture to survive as a perennial. These are conditions that often favour buck’s horn plantain, Yorkshire fog, toad rush and spiny rush (see Figures 10.9 – 10.12). These legumes will not grow in saltier environments where more salt- tolerant species dominate.


The legumes that can tolerate low to moderate salinity (burr medic and lucerne) cannot tolerate waterlogging – conditions that are more suited to barley grass, annual ryegrass, prairie grass or windmill grass (see Figures 10.13 – 10.16)

To assist with the identification of plants that grow on saltland, SGSL developed the SALTdeck cards that include the 50 most common species. These can be viewed on this website .

 Figures 10.9 SALTdeck card for identifying buck’s horn plantain 

Figures 10.10 SALTdeck card for identifying Yorkshire fog 

Figures 10.11 SALTdeck card for identifying toad rush 

Figures 10.12 SALTdeck card for identifying spiny rush 

Figures 10.13 SALTdeck card for identifying barley grass

Figures 10.14 SALTdeck card for identifying annual ryegrass 

Figures 10.15 SALTdeck card for identifying prairie grass 

Figures 10.16 SALTdeck card for identifying windmill grass

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Soil and climate requirements

Table 10.1 shows the minimum rainfall requirements for the main salt-tolerant legumes, and soil salinity and pH levels beyond which productivity is compromised. These figures are a guide only, as seasonal rainfall distribution, maximum temperatures, soil types, and topography will all be important influences. For annual pasture legumes the critical site salinity measurement is in the surface 10cm during early autumn, reflecting the highest levels of salinity that the regenerating pasture seeds might be subjected to at germination. It is more difficult to prescribe the optimal time and soil depth for determining perennial plant suitability on saltland.

Table 10.1 – Rainfall and salinity levels for different legume species and varieties

 

Paradana balansa 

Bolta balansa 

Frontier balansa 

Persian clovers 

Palestine
strawberry clover 

Lucerne 

Burr medic 

Melilotus albus 

Annual Rainfall 

450 - 700 

>600 

350 - 500 

 

>600 

>325 

325 - 450 

>500 

Soil salinity
tolerance levels
ECe (dS/m)
prior to break of season

<8 

<8 

 <8

<9 

<10 

<10 

Soil pH (CaCl2

4.5 - 8.0

5.0 - 8.0 

5.5-9.0

>5.3   

5.2-8.5

>5.6  

Because salinity is often associated with waterlogging, it is generally more meaningful to consider not just salt tolerance but saltland capability which takes account of both constraints.

Despite limited options, most saline areas have access to at least one well-adapted pasture grass, which can form the basis of a productive pasture, and sometimes there are legumes that can form part of that pasture across some of the less saline parts of the site.

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Waterlogging and surface water management

There are no general rules for the management of surface water for legumes on saltland. Balansa, Persian and strawberry clovers are highly tolerant of waterlogging and innundation, provided some of the plant is above the water level. Burr medic, lucerne and Melilotus albus are quite the opposite and do not tolerate prolonged waterlogging. 

Surface drainage can be of value in allowing initial access to the site for establishing the pasture whether the individual species are waterlogging tolerant or not. Deeper groundwater drains may prove to be a disadvantage to strawberry clover, potentially depriving the pasture of moisture in early summer, but reducing the risk of waterlogging could also open up opportunities for lucerne. Such drains present legal challenges in many jurisdictions and local advice should be sought.

The Esperance Downs Research Station in WA provides a good illustration of how surface water management can greatly influence the establishment and management of legume-based pastures on land that rapidly becoming increasingly salt-affected. Melilotus albus has also performed well in western Victoria on raised beds that allow waterlogged soils to be drained.

Plants in low or summer-dominant rainfall regions are generally less at risk of waterlogging stress than plants in high rainfall areas of southern Australia, which might spend months in waterlogged conditions through winter. Research conducted at Tamworth has shown that lucerne in particular can be significantly more productive on saltland when waterlogging is not an issue.

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