THE INFLUENCE OF APPLIED NITROGEN ON THE VIGOR OF LOLIUM-PERENNE DURING THE ESTABLISHMENT YEAR UNDER SUBTROPICAL CONDITIONS

The vigour of Lolium perenne during its establishment year was evaluat ed under subtropical conditions. Both plant and individual tiller vigo ur were monitored under nitrogen (N) applications ranging from 120-720 kg/ha/yr. Plant vigour, as indexed by etiolated growth per unit area, increased with increasing levels of applied N up to 480 kg/ha/yr. Inc reasing levels of applied N increased tiller density, but reduced indi vidual tiller vigour. Irrespective of treatment effects, vigour in per ennial ryegrass under subtropical conditions during the establishment year declines during mid- to late summer.