Tall fescue turfs generally persist during extended periods of drought even though they typically have a greater evapotranspiration (ET) rate than do other cool-season turfgrasses (Horst et al., 1997). Research suggests that a large number of roots in the deeper root zone and an ability to maintain ET as soils dry are two important factors in this drought resistance (Carrow, 1996). A decline in canopy net photosynthetic rate, leaf photochemical efficiency, and the relative water content of leaves occurs much earlier for perennial ryegrass than for tall fescue when both species are exposed to heat and drought stresses (Jiang and Huang, 2001).
With increasing demand for water by municipalities and industry, water availability for turf irrigation will become increasingly scarce, even in areas that are not semiarid or drier. Although drought avoidance is a valued feature of the species, it is important that newer tall fescue cultivars maintain their desired characteristics while minimizing the use of irrigation water during periods of insufficient rainfall. Recently, a comparative study of the hybrid bluegrass cultivars HB 129 and HB 329 and the tall fescue cultivars Southeast and Rebel III revealed that the hybrid bluegrass cultivars were able to survive stress periods better than the two fescue cultivars (Dane et al., 2006).
Several models developed to predict tall fescue ET are incorporated along with soil moisture sensors into automatic sprinkler irrigation systems. In Kansas, the Doorenbos-Pruitt-Makkink (DOOR), FAO-Penman (FAOP), and Penman (PEN) model predictions were highly correlated to ET determined in lysimeters (isolated soil columns) in turfs of three tall fescue cultivars maintained at mowing heights of 6.4 or 7.6 cm (2.5 or 3.0 in) (Fry et al., 1997). In California, Watermark (Irrometer Co., Riverside, CA) granular matrix sensors and neutron probes were used to study the influence of irrigation scheduling on the performance of tall fescue (Richie et al., 1995). The frequency of irrigation, two, three, or four times per week, did not affect the visual quality of turf irrigated at 80% of ET for 4.3 mo.
One irrigation philosophy is to water the entire root zone thoroughly to promote deep rooting. The soil is moistened to a depth of at least 15 cm (6 in), and the turf is not irrigated again until symptoms of drought stress begin to appear. Many professionals managing turfs in loam soils set irrigation systems to apply 1.3 cm (0.5 in) of water no more than twice a week. When thoroughly irrigating tall fescue maintained on slopes or in heavy clay, it may be necessary to activate sprinkler heads intermittently per irrigation event to avoid runoff.
Another irrigation philosophy, based in part on Michigan State University research conducted on Kentucky bluegrass (Lyman et al., 2002), is to irrigate lightly and often during summer, for example, 2.5 to 5 mm (0.1-0.2 in) of water every other day. The goal is to meet the daily water requirement of shallow-rooted plants while conserving water by preventing runoff and the percolation of water below the turfgrass root zone. Excessive moisture and standing water, especially during hot, humid weather, can intensify development of some diseases (Golf Course Irrigation Practices Workgroup, 2007).
Leaf pathogens often require at least 10 h of free water to germinate and infect turfgrasses (Elliott, 1995). Results of research conducted in tall fescue turfs in Kansas suggest that brown patch (caused by Rhizoctonia solani) is largely unaffected by irrigation frequency and clipping management, and that several fungicide strategies can be used to lessen disease severity (Settle et al., 2000).
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