The productivity and persistence of perennial grass species and individual cultivars of tall fescue [Schedonorus arundinaceus (Schreb.) Dumort., nom. cons] and orchardgrass (Dactylis glomerata L.) were evaluated in response to early‐season irrigation termination. Twenty‐five perennial grass species/cultivars were evaluated under three irrigation regimes (full‐season irrigation, early cutoff, and mid‐season cutoff) over 3 yr at the Intermountain Research and Extension Center in the Klamath Basin, CA, on Tule Basin mucky silty clay loam (Andaqueptic Haplaquolls) in a cool temperate climate. Forage grasses included: 10 tall fescue cultivars, seven orchardgrass cultivars, four bromegrass species (Bromus spp), three wheatgrass species (Thinopyrum spp. and Elymus hoffmannii K.B. Jensen and K.H. Asay), and festulolium [×Festulolium loliaceum (Huds.) P. Fourn.]. Tall fescue cultivars were the highest yielding under full irrigation but the most drought tolerant species, tall wheatgrass [T. ponticum (Podp.) Z.‐W. Liu and R.‐C. Wang], intermediate wheatgrass [T. intermedium (Host) Barkworth and D.R. Dewey], and smooth bromegrass (B. inermis Leyss.), performed better with an early‐season irrigation cutoff. There were significant differences in stand persistence among species and cultivars. Stand density for all orchardgrass cultivars declined with each progressively earlier irrigation cutoff date. Plant population for summer active tall fescue cultivars was unaffected by irrigation cutoff date, while stand density for both summer dormant cultivars was higher with the earliest irrigation cutoff. Smooth bromegrass, tall wheatgrass, and intermediate wheatgrass stands were also improved with an early irrigation cutoff. Overall, tall fescue appeared to be the best grass species for variable irrigation water supplies—highly productive under full irrigation when water supplies are adequate, reasonable production with an early season cut‐off in drought years when water is scarce, and good persistence under both full and partial season irrigation.
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