Response of a perennial grassland to nitrogen and phosphorus additions in sub-tropical, semi-arid Australia

Abstract

Soils of arid and semi-arid Australia are typically low in both N and P relative to arid zones elsewhere. We examined relative limitations of N and P on productivity of two native perennial grasslands of sub-tropical, semi-arid, north-west Australia. Effects of single and combined additions of N (50 kg ha-1) and P (25 kg ha-1) on growth and plant nutrients were documented over 2 years. Addition of N alone significantly increased total cover, above-ground biomass, N concentrations and N content, in the first year following above-average summer rains. These effects persisted into the second growing season but were of reduced magnitude. Addition of P alone increased P concentrations and abovegr..