Phosphate deficiency is very marked in Australian soils, particularly in the southern half of the continent. The annual usage of superphosphate in Australia is just over two millions tons, approximately 65 per cent of which is applied to pastures. Each year, therefore, landholders are spending something like £40 million on the purchase, transportation and application of this fertilizer. The present considerations refer mainly to the use of superphosphate on pastures in the higher rainfall sheep areas, where there are very extensive areas of low fertility soils in climatic zones favourable for the growth of various introduced pasture species. In such areas, particularly during the last ten years, many landholders have used substantial quantities of superphosphate to ensure satisfactory establishment and growth of sown pasture species, the most notable of which is Subterranean Clover (Trifolium Subterraneum L.). Widespread success in pasture establishment has led to more intensive production and many landholders, because of higher capital and annual costs, are now conscious of the need for more precision in the use of superphosphate. Lower farm incomes and the consequent limiting of expenditure on superphosphate bring into sharper focus the problem of how best to use this fertilizer, having regard to financial limitations on the quantity that can be used on the property and, also, to the previous treatments of the various paddocks. This problem is of great importance; firstly, because superphosphate is a major cost item (and one which is likely to be reduced when incomes are low), and, secondly, because the rate of superphosphate application is an important determinant of the yield, botanical composition and seasonal growth pattern of pasture.


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