Phosphorus requirements of Australian native plants

The phosphorus (P) requirements of Australian plants are reviewed. Many Australian plants have highly developed abilities for acquiring and conservatively using P. This is seen as an evolutionary response to the combined environmental pressures of fire, soil P levels that are in the lower part of the range for world soils, and low and eratic rainfall. In natural Australian ecosystems, more than 50% of the P in the A horizon is in organic combination. Organic matter is the main source for the growth of perennial plants, so the only successful assessments of ‘available’ P measure labile organic P and microbial P. However, the inorganic P of ashbeds is essential to the rapid establishment of fire ephemerals and tree seedlings in natural ecosystems. Almost all Australian plants develop associations with mycorrhizal fungi, or produce hairy roots, as ways of increasing P uptake. Highly developed abilities to redistribute P from ageing to young tissues enable Australian plants to have a low P requirement per unit of biomass production. This also results in low P losses in sawlogs from natural forests, but not necessarily from short-rotation plantations. The special role of P in the ecology and conservation of heathlands is reviewed. Finally, an overview is given of the P requirements of Australian plants being grown in soil-less media in nurseries.