Js. Bailey, Influence of sward botanical composition on performance of cool temperate grassland under contrasting nitrogen fertilization regimes, COMM SOIL S, 31(17-18), 2000, pp. 2855-2864
Eight field experiments, which tested the effects of lime, phosphorus (P),
and two rates of nitrogen (N) on a range of permanent grassland swards in N
orthern Ireland (NI), were re-examined to investigate the influence of swar
d botanical composition on aerial dry matter (DM) productivity under 'low'
and 'high' levels of N input. The aim of the investigation was to verify re
sults previously obtained using 'pure' single-species swards, which suggest
ed that secondary grasses are more productive than perennial ryegrass at lo
w levels of N input (i.e., <100 kg N ha(-1) a(-1)). The swards used in the
investigation varied considerably in botanical composition, but were largel
y dominated by three main species: perennial ryegrass (Lolium perenne L.),
creeping bent (Agrostis stolonifera L.), and rough stalked meadow grass (Po
a trivialis L.), all of which were characteristic of fertile habitats. The
results confirmed that under reduced N input management, swards dominated b
y these secondary grasses are capable of out-performing those in which pere
nnial ryegrass is a major component. The superior (aerial) productivity of
the secondary grasses was attributed to their ability to conserve resources
and maintain high shoot-to-root ratios under 'moderate' N stress condition
s.