Consumptive water use and stomatal conductance of Atriplex lentiformis irrigated with industrial brine in a desert irrigation district

Abstract The halophyte forage shrub, Atriplex lentiformis (quailbush), was irrigated with brine from a reverse-osmosis (RO) water treatment plant in an agricultural district in Marana, Arizona, in the Sonoran Desert, U.S. Small transplants were installed in large, outdoor drainage lysimeters and drip-irrigated with RO concentrate, on a schedule designed to deliver 1.5 times the reference evapotranspiration (ET 0 ) on a daily basis, as determined by an on-site micrometeorological station. Water consumption was measured by a water-balance approach over an annual cycle and by measuring sap flow with heat-balance sensors over a 28-day period in August 2008. Over this annual cycle, biomass yield was 1.62 kg m −2 and the average water consumption during the growing season was 1.55 times ET 0 , similar to values for high-biomass crops such as alfalfa. The drainage fraction (water that exited lysimeters) was only 5% of the total input (irrigation plus precipitation) over the study. The Priestley–Taylor coefficient relating evapotranspiration (ET) to net radiation was 1.34, typical of values for freely transpiring crops under non-water-limiting conditions. Rates of transpiration measured by sap flow sensors were closely coupled to both solar radiation and atmospheric water demand on hourly and daily time steps. Stomatal conductance was high throughout the day and coupled to diurnal solar radiation. Although halophytes often exhibit low to moderate growth potential under natural conditions or in sub-optimal agricultural settings, the present results show that they have high growth potential when water and nutrients are not limiting. The high yield and consumptive water use by A. lentiformis makes it a good candidate for the reuse of industrial or agricultural brines in arid-zone irrigation districts.