Influence of applied nitrogen on vegetative, reproductive, and aerial tiller densities in Lolium perenne L. during the establishment year

Abstract

The influence of applied nitrogen (N) (120-720 kg/ha · year) on Lolium perenne (perennial ryegrass) vegetative, reproductive, and aerial tiller densities was monitored during the establishment year under grazing. Total (vegetative, reproductive, and aerial) tiller densities ranged from 3500 tillers/m² (at 120 kg N/ha · year) during April 1994 to 17 800 tillers/m² (at 600 kg N/ha · year) during August 1994. Increasing levels of N (up to 360 kg N/ha · year) increased total tiller density. Reproductive tillers were observed in November and December 1993 and ranged from 6 (at 600 kg N/ha · year) to 27 (at 480 kg N/ha · year) tillers/m². Nitrogen levels above 240 kg/ha · year promoted reproductive tiller development, whereas levels above 600 kg/ha · year depressed reproductive tiller development. Since the low reproductive tiller densities resulted 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/m² in September 1994. Increasing levels of applied N increased aerial tiller density, whereas at low levels (120 and 240 kg N/ha · year) aerial tillering was negligible.