Abstract
Perennial ryegrass (PRG), Lolium perenne L. and tall fescue (TF), Festuca arundinasea Schreb. were sown separately and in a mixture at high and low densities (HD and LD) in order to find the relation between degree of species competition and leaf area index (LAI). At HD, competitive effects were observed 7th week after sowing, when LAI was 1.95 in a mixture, in such a way that both dry weight and leaf area per plant were negatively biased in TF, a suppressed species and positively biased in PRG, an aggressive one (Figs.2 and 3, Table 1). At LD, however, the effects were not so clear at that time, when LAI was 1.18, because of low competitive-values of TF. The same LAI of 1.18 had been shown already 5th week after sowing in a mixture of HD, when little effect of competition had been found. Eleventh week after sowing, when LAI reached 2.6, the effect of competition was clearly found. Therefore competition would presumably begin to occur as soon as LAI reached 1.5 to 2.0. At LD 11th week after sowing the growth of TF was more severely suppressed by PRG growing more aggressively than before. This shows the advance of competition with the increase of LAI. At HD, however, competitive-values of 11th week were almost the same as those of 7th week, in spite that LAI reached such a high level as 5.8. This may be caused by the diminished effect of competition due to the increased density effect. The advantage of PRG or the disadvantage of TF in competition was derived from the difference of the rates of emergence and seedling growth (Table 2).
