Waterlogging and poor soil structure in the root-zone of duplex soils in Western Australia has long been recognised as a major constraint to the production of agricultural crops and pastures. The effect of raised beds on waterlogging, soil structure, and productivity of duplex soils was investigated. Five experimental sites were established, monitored, and operated over 5 years as well as 3 larger scale demonstration sites which were operated over 4 or 3 years. Treatments consisted of raised beds and a normal no-till seed bed as the control. The beds were made with a bed former after the soil had been deep cultivated. Bulk density and steady-state infiltration rate observations indicated significant and lasting improvements in soil structure in the beds. The incidence of waterlogging in raised beds was reduced and this was accompanied by an increase in runoff from the raised beds. The average grain yield increase from the beds was 18% for a variety of crops across a range of climatic conditions and duplex soils. Seven years after the introduction of raised beds for broad-acre farming in Western Australia, more than an estimated 30 000 ha of crops is now grown on raised beds.
Australia’s traditional approach to salinity abatement has been to focus primarily on the control of recharge in land not at risk of salinity by incorporating deep-rooted perennial plants (e.g. lucerne, oil mallees and farm trees) into farming systems throughout the landscape. However, in the broad valley floors and sedimentary plains of Australia’s cropping regions (the areas most at risk of salinity), recharge is mainly a 1-dimensional process. Thus, offsite recharge management may have little or no impact on salinity outcomes for the areas at risk. The future of the broad valley floors will be most influenced by the management decisions of landholders in the valley floors.
To be sustainable and profitable, farming systems on valley floors need to (i) target perennial plants to the valley floors and improve soil management to dry the root-zone, decrease recharge and minimise capillary rise, (ii) increase the discharge of groundwater from valley floors using deep drains and stands of perennial plants, (iii) improve surface water management to ameliorate waterlogging, inundation and flooding, and (iv) incorporate better plants and better agronomic methods in the growth of profitable salt tolerant crops and fodder plants.
This paper will illustrate the convergence of new research and development that offers real prospects of low risk, high return farming systems for Australia’s threatened valley floors. We argue that there needs to be a major refocus by farmers, researchers and their funders in the development of profitable sustainable farming systems for valley floors.
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