Diagnosing salinity in canola
Salinity affects growth by reducing plant root ability to extract water from the soil, and chloride toxicity. Salinity damage varies from season to season due to variations in soil salt concentration as waterlogging increases salinity effects.
What to look for
- Moist bare patches where seed has failed to germinate or seedlings have died.
- Patches of stunted and apparently water stressed or prematurely dead plants in areas subject to salinity.
- Most crop weeds will also be affected with the exception of salt tolerant species.
- Salt crystals may occur on dry soil surface.
- Symptoms vary with soil salt concentration and severity of waterlogging.
- Plants on waterlogged but mildy saline areas will appear to be nitrogen deficient with pale plants having uptight growth and reddened or yellow older leaves.
- As salinity increases, plants will be more stunted with orange-yellow older leaves that die back from the end and edges.
- Roots die back and are more susceptible to fungal rot
- Plants are more liable to lodge and mature prematurely.
What else could it be
|Diagnosing waterlogging in canola||Most saline areas also intermittently waterlogged; poor emergence, pale seedlings.||Waterlogging in non-saline areas causes nitrogen deficiency leaf symptoms|
|Diagnosing damping off in canola||Poor emergence, dying or stunted seedlings, orange-red oldest leaves that die back from edges. Damping off is more common in wet areas.||Plants with a pinched hypocotl or root and not restricted to saline areas|
Where does it occur?
- Primary salinity:
- 1. This occurs on heavy textured, highly alkaline and usually well-drained soils with high levels of salt in the subsoil. Most common are aeolian morrell-blackbutt loams on the edge of major wheatbelt valleys or greenstone soil and clay soils in the Esperance mallee. Being highly alkaline, there is an enhanced risk of canola damage from group B herbicides remaining in the subsoil.
- 2. These soils can yield well in wet seasons and be the worst yielding soils in dry seasons, due to high topsoil evaporation and salt osmotic pressure.
- 3. High subsoil boron levels also affect cereals on these soils but canola is more tolerant.
- Secondary salinity:
- 1. Salinity has been caused by salt accumulation from saline watertables or see-pages that have increased after land clearing.
- 2. Soils vary but are frequently duplex or heavy textured.
- 3. Salinity is frequently accompanied by waterlogging in autumn and winter, which greatly increased plant damage.
- Naturally saline soils cannot be ameliorated but managed according to season and their capability.
- Canola is poorly adapted to soils with secondary salinity.
- Engineering solutions such as drainage may be possible for secondary salinity but must be assessed on a site by site basis
How can it be monitored?
- The salinity status of a soil can be assessed from indicator plants, measuring the salt concentration in soil samples or with electromagnetic-induction instruments or by measuring the depth to a saline watertable.
Where to go for expert help
Page last updated: Tuesday, 20 January 2015 - 10:46am