Improving the Efficiency of P Fertilizers in Dryland Cropping Systems in Mediterranean Climates.

Australian soils in their natural state are deficient in phosphorus (P), and the production of healthy agricultural crops has required the regular addition of P fertilisers. Indeed, the main sources of P present in Australian agricultural soils are derived from the application of manufactured fertilisers. In some areas, the available pools of soil P have been built up to levels where rates of P application can be reduced to “maintenance”, while in others there is a continuing requirement for regular additions of P over and above maintenance application rates. With the increasing cost of P fertilizer inputs, various technologies have been suggested to improve P efficiency, but few have provided solid field evidence for efficacy.  This paper discusses these approaches and examines the possible means to improve P efficiency in cropping systems in dryland environments.