Land and Resources, Soils
leguminous plants, soil acidification, Great Dividing Range, salinization, Wind erosion
All major soil types are present to varying degrees throughout the continent. The arid and semiarid regions provide the most extensive group of soils. These soils are mainly suitable only for light livestock grazing. Most useful for this purpose are some of the desert loam areas of South Australia and New South Wales and the arid red earths of south central Queensland, northern New South Wales, and northern South Australia. The vast areas of stony desert, sand plain, and sand hills that cover the bulk of central Australia are of very little or no use for livestock. Soils of the semiarid zones include heavy-textured gray and brown soils in northwestern Victoria that support productive farming of grains and other crops. Soils of the humid and seasonally humid zones occupy a much smaller portion of the land area, including the Great Dividing Range, east central Victoria, and Tasmania.
Only 6.2 percent of Australia’s total land area is arable. Because of extensive leaching of minerals, especially in areas of higher rainfall, most Australian soils are not particularly fertile. Phosphate and nitrogen are widely lacking, and large areas lack trace elements necessary for crop nutrition. To address these deficiencies, phosphate additives have been used extensively as soil fertilizers for many years, and leguminous plants such as subterranean clover are grown to add nitrogen to the soil. In addition, large areas of marginal land have been made more productive by the addition of trace elements, such as zinc, copper, and manganese. However, water runoff from fertilized soils has been linked to periodic outbreaks of toxic blue-green algal blooms in the Murray-Darling Basin, and the growing of subterranean clover has led to soil acidification through the leaching of nitrates.
Soil erosion and desertification due to poor farming practices have occurred in many areas, especially on overgrazed and logged land. Wind erosion in the semiarid pastoral and agricultural regions and water erosion in the wetter, deforested southeastern regions also pose major problems. Salinization and alkalization of soil is another common problem because Australia has few large, permanent rivers for irrigation. A large amount of irrigation water comes from wells that tap underground artesian basins, most of which supply somewhat saline water of poor to marginal quality.
A nationwide community-based movement called Landcare won significant government support, at federal and state levels, to address these problems, and the 1990s was officially declared the Decade of Landcare. The Landcare movement has harnessed local skills to tackle urgent problems such as soil erosion and salinization. Important gains include increased attention to the need for innovative, adaptive farming practices. In 2001 there were more than 4,500 community Landcare groups, all federally assisted under National Landcare Program funding as part of the Natural Heritage Trust.
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