Effect of Artificial Drought on Sward Tiller Density in Lolium and Festuca

Eight grasses, grown in field swards, were compared in four replicates on each of two adjacent sites. One site received normal rainfall; the other site was protected from rain by plot covers of clear polythene from June 1990 (the year after sowing) to October 1991. All plots were cut every 5 weeks from March to October. The numbers of tillers of the sown species per 0.1 m2 were recorded on all plots four times in the period September- December 1990 and four times in the period March-October 1991. The drought conditions created by the covers reduced the numbers of tillers in aU eight grasses. In proportional terms, Westerwolds ryegrass, Italian ryegrass and meadow fescue were the most severely affected, followed by Italian ryegrass x meadow fescue and Italian ryegrass x perennial ryegrass; then came perennial ryegrass, followed by perennial ryegrass x meadow fescue; tall fescue was much the most drought resistant of the eight.