Likely situations for sub-tropical grasses

 

1.     Salinity and waterlogging
It is generally considered that Rhodes grass and kikuyu have similar salinity tolerances, though NSW information has indicated that saline irrigation water reduced Rhodes grass growth more than kikuyu. Both grow best in non-saline soils but will grow well in soils with low salinity (2-4 dS/m) and to a lesser extent in soils with moderate salinity (4-8 dS/m).

Rhodes grass as it has poor tolerance to waterlogging.

Most likely situation for sub-tropical grasses with limited salinity tolerance.

Subsoil salinity/ depth to watertable matrix

 Winter

Summer 

 

 

Drivers of plant zonation

  • Non-halophytes so limited salinity tolerance
  • Tolerate some waterlogging in winter – kikuyu more than Rhodes grass
  • Growth in summer assisted if low salinity groundwater accessible to roots
  • Rainfall 400-600mm

 


Key to symbols

red dot

This is the zone most preferred by the temperate grasses with limited salinity tolerance and where they are highly recommended;

Small Dot

The temperate grasses with limited salinity tolerance are one of the possible options for this zone but it is outside their preferred conditions


2.     Climate and soils
Kikuyu and Rhodes grass are C4 species that require temperatures >15 Co for their photosynthetic pathway to operate, meaning they are only suited to coastal regions, to the northern agricultural region in WA, and to central and northern NSW.

Both species prefer frost-free climates, but will survive in frost-prone areas that have summer rainfall. Kikuyu is highly drought-resistant, but Rhodes grass has only fair tolerance to drought.

Rhodes grass and kikuyu are widely adapted across many soil types but perform best on light to medium textured soils as establishment difficulties have been reported on heavy soils. Soils need to be reasonably well drained for Rhodes grass as it has poor tolerance to waterlogging - kikuyu is more tolerant of waterlogging and acid soils.

3.     Indicator species
The ‘classical’ indicator species for saltland all tend to indicate levels of salinity and/or waterlogging that will exceed the tolerance of the sub-tropical grasses such as Rhodes grass and kikuyu.

The most likely indicator species are barley grass, annual ryegrass or windmill grass (a native, warm season grass), though these species are quite widespread in non-saline environments and are therefore very weak indicators.

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