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 plan t: mildly saline (1149 mgl(-1) total dissolved solids (TDS)) storm run off collected in a pond, or brackish (4100 mgl(-1) TDS) blowdown water from cooling towers. Plants were irrigated weekly with enough water t o replace evapo-transpiration losses but leaching fractions were only 4-10%. Atriplex nummularia performed equally well. on both water sourc es, even though soil solution salinity in the rooting depth profile ra nged from 300-1000 mol m(-3) NaCl in lysimeters irrigated with blowdow n water compared to only 40-90 mol m(-3) in lysimeters irrigated with pond water. Atriplex nummularia had higher productivity, water use eff iciency and consumptive water use than conventional forage crops in Ar izona irrigation districts. Nutritional content of plant tissues was a cceptable for use as a ruminant forage. Atriplex nummularia had key tr aits desired in a plant for disposal of saline water: high consumptive use to minimize land area devoted to reuse; high salt tolerance, conf erring the ability to grow under low leaching fraction to minimize dis charge to the aquifer; and useful production. (C) 1998 Academic Press Limited.