Dryland salinity in south-western Australia: its origins, remedies, and future research directions

Replacement of deep-rooted, perennial native vegetation with shallow-rooted, annual agricultural plants has resulted in increased recharge causing shallow saline water tables leading to dryland salinity and loss of agricultural production. Restoring the vegetation by regeneration or replanting lowers water levels locally but field evidence and computer modelling suggests this needs to be widespread for regional effects, which conflicts with the future of conventional agriculture. Alley farming allows agriculture to be continued in the bays between the rows, but needs as much perennial, preferably deep-rooted, vegetation as possible in the bays to achieve the required recharge reductions. Where the asset to be preserved is valuable and a means of safe saline effluent disposal exists, pumps and drains will be part of any salinity management system, but where these conditions are not met they will be of limited use on an economic basis. To limit the spread of dryland salinity substantial change in farming systems is required and farmers need assurance that the recommended strategies will have the desired effect. Computer modelling is the only timely way to do this. An operationally simple 1-dimensional model already exists, and a 2-dimensional one is under development and testing. Three-dimensional modelling is also probably required to support strategic, intensive interventions.