Review of phosphorus availability and utilisation in pastures for increased pasture productivity

Summary

The P-balance efficiency of southern Australian agriculture is only ~25% (i. e. 4 units of P are applied as fertiliser to produce only I unit of P in products). Inefficient P-use represents both a threat (graziers who use P-ineffectiveIy will be viewed poorly in a P-limited world) and a major opportunity (efficiency measures will improve profitability and coinpetiveness). Reductions infertiliser inputs, in the first instance, of 25%-30% with concomitant environmental benefits appear feasible. However, this will require a committed RD&E investment. Wider implementation of industry best-practice can provide immediate benefits, To secure continued improvements it will be necessary to research the development of novel, lower-P farming systems, novel fertilisers orfertiliser management technologies, alternative P-efficient pasture legumes and P-efficient varieties of Australia's keystone pasture legumes.
Australia's extensive northern rangelands are P-deficient with few economic options for using P-fertilisers. A desktop audit indicated that the systems are all likely to be slowly extracting P without replacement. In most cases, the rates of P loss are low and riot a threat to production at the present time. However, where productivity is higher nutrient extraction is thought to be a factor in the effective collapse of grazing system productivity and the issues of P extraction andreplacement need to be explored. Direct strategic P supplementation of cows in extensive breeding systems is likely to lift productivity and to bring the P-balance of these systems closer to an 'ideal' P-balance efficiency.