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The management of nutrients for pastures

D. Lewis and P.W.G. Sale

Department of Agriculture, Naracoorte, SA 5271 School of Agriculture, La Trobe University, VIC 3083


To remain viable in the face of the continuing cost price squeeze, wool producers must increase their production efficiency. By definition this involves careful management of inputs to maintain or increase wool production. Phosphate (P) fertiliser is the major input required to maintain pasture productivity, and efficient use of fertiliser (in terms of animal production per unit of applied nutrient) must demand increasing attention from Australian researchers. The stocking rate by P rate interaction provides a model for examining improvements in biological and economic efficiencies that are possible with high (P) fertility, heavily stocked pastures containing productive, P responsive species. Ecological impacts and long term viability, and beneficial outcomes, of high stocking rates on such pastures is examined and the research initiatives required to enable producers to benefit from high input/high output systems, are discussed.

Improvements in the economic efficiency of P applications may be possible if Australian wool producers replace single superphosphate with alternative forms of P fertilizer. Use of reactive phosphate rock (RPRs) and to a lesser extent, high analysis P forms may lead to substantial cost savings. However, the success of any RPR strategy will depend on the soil/climate/pasture environment in which the RPR is used as high dissolution rates of this material are essential for it to be an effective fertiliser. The magnitude of any cost savings from alternative P forms will also depend on sulphur requirements of pasture. New diagnostic procedures for S and a greater understanding of the S requirements of different pasture systems, arc required if cost savings are to be gained from alternative P forms. Potassium, like sulphur, is a very mobile nutrient, and product form and management strategies must be developed to improve efficiency of K application.

Identification and correction of trace element deficiencies of newly sown pastures is reasonably simple, but maintaining adequate supplies of these nutrients in established pastures is more difficult. Development of diagnostic tests has helped but research needs to be continued to gain a better understanding of the complexities of trace element nutrition of both plants and animals.

The interactions between plant nutrition and acidification of many light textured soils is discussed.

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