Contrasting Urban Landscapes and Reduced Irrigation Engender Water Conservation in a Desert Environment

With increased interest in water conservation, traditional residential landscapes, which often include turfgrass and other high-water use plants, are often eliminated in favor of low water use desert landscape plants. But even with a desert landscape, home owners often overwater, thereby reducing any water conservation possibility. This experiment was designed to demonstrate that plants can retain physiological health even when on reduced irrigation. Three 26.8-m2 plots each of two contrasting landscapes, designated as either traditional or desert, were installed in a desert environment using a pot-in-pot in-ground system. Plots were irrigated at 100% or 50% of evapotranspiration (ET) with either sprinklers (turf) or drip emitters (trees and shrubs) using a modified crossover design. Midday stem water potentials (Ψmd) for Arizona ash, Indian hawthorn and Cleveland sage exhibited seasonal differences. In Chinese pistache, Ψmd remained stable when irrigation treatments were lowered from late spring/early summer (−0.26 MPa) to late summer (−0.35 MPa). Chinese pistache maintained less negative osmotic potential when irrigation increased from 50% ET (−5.13 MPa) to 100% ET (−3.68 MPa) in early fall. The ability of Chinese pistache to maintain Ψmd and osmotic potential may indicate this species’ resilience to drought. Surprisingly, Arizona ash sustained greater relative water content in late fall when irrigated at 50% ET (92% elative water content (RWC)) than when irrigated at 100% ET (76% RWC) and this might be due to osmotic adjustment. The plants used in this study recovered after two weeks of full (100% ET) irrigation suggesting that landscape managers could irrigate at 50% ET for a limited period (approx. four weeks) as a way to conserve water