Effect of moisture deficit on four perennial ryegrass cultivars

The effect of moisture deficit on herbage production, root growth, tiller density, leaf appearance, percentage dry matter, and water-soluble carbohydrate (WSC) concentration and content in the stubble of Epichloë endophyte-infected perennial ryegrass plants (cultivars Aberdart AR1, Bealey NEA2, One50 AR37, Trojan NEA2) was investigated in a glasshouse study. Water was withheld from half the plants for 6 weeks, followed by a 4-week recovery period, when all plants were watered. At the end of the treatment period, there were differences among cultivars in tiller density, moisture content of the herbage, WSC content of stubble, and root mass. However, there was little effect of moisture deficit on these variables or on root depth. At the end of the recovery period, previously moisture-stressed plants had increased leaf appearance by 25%, leafy-herbage mass by 29%, and low molecular-weight WSC content of stubble by 37% compared with well watered plants, but there was a decrease in root mass in some cultivars. There were differences among cultivars in tiller density, the moisture content of the herbage and stubble WSC content. The effects of previous moisture deficit were greatest during the recovery period, and differed among cultivars, for stubble, root and total plant biomass. Results suggested that avoiding overgrazing immediately after drought is just as critical for recovery as is management during a drought, given that the greatest responses to previous moisture deficit were detected during this period.