Physiological Responses of Turfgrass Species to Drought Stress under High Desert Conditions

Broad concerns over water shortages and drought where irrigated urban landscapes are common in high desert regions have focused attention on drought tolerance of turfgrass species. We investigated the physiological responses of kentucky bluegrass (KBG) and tall fescue (TF) under a prolonged drought under high desert conditions. The experimental design was a split plot with three replicates. Two irrigation treatments as a whole plot-well-watered and no water-were applied to subplots of 'Midnight' KBG and 'Gazelle' TF. Stomata! conductance (g(S)), canopy temperature, and predawn leaf water potential were measured over two seasons. KBG g(S) and leaf water potential decreased faster and to a greater extent than TF in response to soil drying, and KBG was in complete dormancy and brown within 5 weeks after cessation of irrigation. By contrast, TF maintained a green canopy throughout the drought periods. In the no-water plots, TF appeared to consume water from the deepest measured soil profiles (80- to 100-cm depth), whereas KBG used most of the water in the 50- to 60-cm depths. When watered for recovery in late summer, KBG plots were mostly green within 3 weeks after rewatering. The surface temperature of the well-watered plots was 6-13 degrees C cooler than the no-water plots and TF showed 5-7 degrees C lower temperature than KBG in no-water plots. TF is suitable for deep soil, exploiting a larger volume of water to avoid drought, whereas KBG's rapid drought avoidance would likely perform better in shallow landscape soils under drought.