AbstractDrought tolerance in turfgrass species and optimal irrigation strategies are key to addressing the need for water conservation in our landscapes. Preliminary findings on tall fescue [Schedonorus arundinacea (Schreb.) Dumort., nom. Cons] in western Oregon have determined that this species can persist at a high‐quality level with very little evapotranspiration (ET) replacement. Research on perennial ryegrass (Lolium perenne L.) in western Oregon has suggested deficit ET replacement is also a viable weed management tool. Considering these preliminary findings, the objectives of this research were to evaluate the effects of reference evapotranspiration (ETref) replacement levels, irrigation intervals, and a no irrigation control treatment on tall fescue appearance and weed encroachment. This research was conducted in western Oregon on a silty clay loam soil. Factors in this experiment included two irrigation frequencies (once or four times a week) and two ETref replacement rates (45% and 80%) compared to a control treatment (no irrigation). The 80% ETref replacement rate resulted in the greatest turf color, followed closely by the 45% ETref replacement treatment. The no irrigation control treatment was able to sustain acceptable turfgrass color for most of the year, with the exception during the month of August. Tall fescue will remain visually acceptable when soil volumetric water content is maintained around 15% or greater in a silty clay loam. The no irrigation control treatment also produced substantial reductions in weed populations (annual and perennial broadleaf weeds and annual grasses).
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