Effects of drought on growth and competitive ability of perennial ryegrass and white clover.
Lolium perenne cv. S23, Trifolium repens cv. S184 and T. repens cv. Olwen were grown in the glasshouse as monocultures and as mixtures. Drought conditions applied 28-56 days after sowing reduced shoot growth of grass and clover monocultures equally, but affected clover more than ryegrass in the mixtures. Droughting 4-5 months after sowing reduced cut herbage wt. of the clovers more than that of the grass. Herbage regrowth of T. repens cv. Olwen was unaffected by previous drought, and that of ryegrass was slightly increased. Regrowth of previously droughted T. repens cv. S184 was twice that of the controls. Clover regrowth in mixtures was suppressed less in previously droughted mixtures than in continuously watered mixtures. It was concluded that during drought in the field the clover content of mixed swards could be maintained by frequent defoliation. The competitive ability of clover during drought could be improved by breeding for greater root density and for the ability to adopt a low defoliation-avoiding habit during dry weather.