Competition between tall fescue and perennial ryegrass in pure and mixed swards under simulated field conditions.
Tall fescue cv. S170 and perennial ryegrass cv. S24 were sown at 1, 2, 4 or 8 seeds per 25 cm2 in pure and mixed stands. Establishment was 81% for S170 and 91% for S24. Plant survival for both species was > 90% after 360 days, but at the end of the trial, 720 days after sowing, survival ranged from 66% at the lowest density to 37.6% at the highest. With S24 in monoculture and in mixture with S170, tiller production per plant was reduced. Increased sowing density greatly reduced tiller number per plant in both pure and mixed stands. There were 2 peaks of tiller production, Apr.-May and Aug.-Sept., and a large fall in tiller numbers as inflorescences appeared. S170 showed no clear autumn flush of tiller production, possibly because of competition and density effects. In S24, low density sowings had lower tiller numbers per unit area before flowering but higher tiller numbers afterwards. Sowing density and number of tillers per plant were inversely related. Yield per plant was greatly reduced by increase in sowing density. S24 plants were lighter when grown in monoculture than when in mixture. Highest yields of S170 were obtained in monoculture. Yield per unit area increased from the 1st to the 2nd sowing density (10 to 20 kg seed/ha) but declined at higher densities. At a given sowing density the yield of the mixture was lower than that of pure S24 and higher than that of pure S170. Location of individual plants within the sward was facilitated by using a wire mesh screen for sowing and subsequent observation.-R.B.