Water use, productivity and forage quality of the halophyte Atriplex nummularia grown on saline waste water in a desert environment

The halophyte Atriplex nummularia Lindl. was grown in a desert climate in Tempe, AZ, for 3 years in outdoor drainage lysimeters. Plants were irrigated with two sources of waste water from an electric power plant: mildly saline (1149 mgl(-1) total dissolved solids (TDS)) storm runoff collected in a pond, or brackish (4100 mgl(-1) TDS) blowdown water from cooling towers. Plants were irrigated weekly with enough water to replace evapo-transpiration losses but leaching fractions were only 4-10%. Atriplex nummularia performed equally well. on both water sources, even though soil solution salinity in the rooting depth profile ranged from 300-1000 mol m(-3) NaCl in lysimeters irrigated with blowdown water compared to only 40-90 mol m(-3) in lysimeters irrigated with pond water. Atriplex nummularia had higher productivity, water use efficiency and consumptive water use than conventional forage crops in Arizona irrigation districts. Nutritional content of plant tissues was acceptable for use as a ruminant forage. Atriplex nummularia had key traits desired in a plant for disposal of saline water: high consumptive use to minimize land area devoted to reuse; high salt tolerance, conferring the ability to grow under low leaching fraction to minimize discharge to the aquifer; and useful production. (C) 1998 Academic Press Limited.