INFLUENCE OF APPLIED NITROGEN ON VEGETATIVE, REPRODUCTIVE, AND AERIALTILLER DENSITIES IN LOLIUM-PERENNE L. DURING THE ESTABLISHMENT YEAR

The influence of applied nitrogen (N) (120-720 kg/ha.year) on Lolium p erenne (perennial ryegrass) vegetative, reproductive, and aerial tille r densities was monitored during the establishment year under grazing. Total (vegetative, reproductive, and aerial) tiller densities ranged from 3500 tillers/m(2) (at 120 kg N/ha.year) during April 1994 to 1780 0 tillers/m(2) (at 600 kg N/ha.year) during August 1994. Increasing le vels of N (up to 360 kg N/ha.year) increased total tiller density. Rep roductive tillers were observed in November and December 1993 and rang ed from 6 (at 600 kg N/ha.year) to 27 (at 480 kg N/ha.year) tillers/m( 2). Nitrogen levels above 240 kg/ha.year promoted reproductive tiller development, whereas levels above 600 kg/ha.year depressed reproductiv e tiller development. Since the low reproductive tiller densities resu lted from frequent intensive grazing, little practical importance can be attached to these results. Aerial tiller densities ranged from 12 ( at 480 kg N/ha.year) in January to 487 (at 720 kg N/ha.year) tillers/m (2) in September 1994. Increasing levels of applied N increased aerial tiller density, whereas at low levels (120 and 240 kg N/ha.year) aeri al tillering was negligible.