Response of drought susceptible and resistant Kentucky bluegrass and tall fescue cultivars and mixtures to limited irrigation

Water consumption and supply for the urban landscape continues to be a concern for many communities throughout the United States. A 2-yr field study was conducted in the cool-humid region to determine the irrigation requirements of drought sensitive (DS) and drought resistant (DR) Kentucky bluegrass (Poa pratensis L.; KBG) and tall fescue [Festuca arundinacea Schreb.; syn. Schedonorus arundinaceus (Schreb.) Dumort., nom. cons.; TF] cultivars maintained at two mowing heights (5.1 or 8.9 cm). Additionally, TF:KBG mixtures 90:10 (w/w) containing DS or DR cultivars were also evaluated. Irrigation was determined using a 70% green coverage threshold (GCT(70)) approach, where turf was imaged twice weekly, and 12.7 mm of irrigation was applied if an individual plot fell below the GCT(70). Time to initially fall below the GCT(70) ranged from 15.4 to 50.0 d and varied by species and cultivar, with TF and the TF:KBG mixtures taking the longest time to fall below the threshold. Total irrigation ranged from 61.9 to 173.9 mm over the 74-d drought events. The DR TF and TF:KBG mixtures containing DR TF required the least irrigation. Mowing height generally had no effect on irrigation requirements of the cultivars or mixtures evaluated in this study. These data reinforce the fact that substantial irrigation can be saved by planting DR species and cultivars and employing a limited irrigation strategy based on a minimum green coverage threshold.