Abstract
More than 60% of the 20 million ha of cropping soils in Australia are sodic
and farming practices on these soils are mainly performed under dryland
conditions. More than 80% of sodic soils in Australia have dense clay subsoils
with high sodicity and alkaline pH (>8.5). The actual yield of grains in
sodic soils is often less than half of the potential yield expected on the
basis of climate, because of subsoil limitations such as salinity, sodicity,
alkalinity, nutrient deficiencies and toxicities due to boron, carbonate and
aluminate. Sodic subsoils also have very low organic matter and biological
activity.
Poor water transmission properties of sodic subsoils, low rainfall in dryland
areas, transpiration by vegetation and high evaporation during summer have
caused accumulation of salts in the root zone layers. This transient salinity,
not influenced by groundwater, is extensive in many sodic soil landscapes in
Australia where the watertable is deep. ‘Dryland salinity’ is
currently given wide attention in the public debate and in government
policies, but only focusing on salinity induced by shallow watertables. While
16% of the dryland cropping area is likely to be affected by
watertable-induced salinity, 67% of the area has a potential for transient
salinity not associated with groundwater and other subsoil constraints and
costing the Australian farming economy in the vicinity of A$1330 million per
year. A different strategy for different types of dryland salinity is
essential for the sustainable management and improved productivity of dryland
farming.
This paper discusses the sodic subsoil constraints, different types of
salinity in the dryland regions, the issues related to the management of sodic
subsoils and the future priorities needed in addressing these problems. It
also emphasises that transient salinity in the root zone of dryland
agricultural soils is an important issue with potential for worse problems
than watertable-induced seepage salinity.
Subject
General Agricultural and Biological Sciences
Cited by
323 articles.
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