Lt. Bennett et Ma. Adams, Response of a perennial grassland to nitrogen and phosphorus additions in sub-tropical, semi-arid Australia, J ARID ENV, 48(3), 2001, pp. 289-308
Soils of arid and semi-arid Australia are typically low in both N and P rel
ative to arid zones elsewhere. We examined relative limitations of N and P
on productivity of two native perennial grasslands of sub-tropical, semi-ar
id, 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 documen
ted over 2 years. Addition of N alone significantly increased total cover,
above-ground biomass, N concentrations and N content, in the first year fol
lowing 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 aboveground P content but had negligible effects on b
iomass, indicating luxury consumption. Combined addition of N and P had sim
ilar effects to addition of N alone, strengthening the argument that N and
not P was limiting to growth. Nitrogen limitation was clearly indicated by
low N to P ratios (< 7) in aboveground plant components. (C) 2001 Academic
Press.