Comparative Evapotranspiration Rates of Tall Fescue Cultivars

Comparative evapotranspiration (ET) rates of 20 cultivars of tall fescue (Festuca arundinacea Schreb.) were measured over 7 days in a greenhouse study. Small but significant differences in ET rates existed between the cultivars grown under non- limiting water and nutrient conditions on day 1 following mowing. Greater differences had developed after 7 days of growth, with ET ranging from a low of 10.0 mm·day -1 -1 for 'Alta'. Day 7 ET was positively correlated (r = 0.82) with clipping dry weight. Six of the tall fescue cultivars were selected for a subsequent experiment to determine the stability of relative rankings for ET over time. Although average ET varied by up to a factor of two among five dates, the rankings were nearly identical for the five dates and were consistent with the rankings in the first experiment. Mounting concern over the distribution of finite water supplies in the western United States underscores the importance of select- ing turf species and cultivars with low water use rates. Numerous investigators have com- pared evapotranspiration (ET) rates between species (Aronson et al., 1987; Biran et al., 1981; Kim and Beard, 1988). Fewer pub- lished studies have examined intraspecific differences. Shearman (1986) reported rela- tively large differences in ET rates within 20 Kentucky bluegrass (Poa pratensis L.) and 12 perennial ryegrass (Lolium perenne L.) cultivars (1989). Tall fescue is becoming an increasingly popular turfgrass due in part to desirable leaf texture, color, shoot density, and mowing qualities. In a recent field study, Kopec et al. (1988) investigated ET rates of six tall fescue cultivars using mini-lysimeters and found that the four turf-type cultivars used an average of 6% less water than the two forage types. The present greenhouse study was undertaken to evaluate water use rates of recently developed cultivars of turf-type tall fescues. A second objective was to de- termine the stability of cultivar rankings over time.