Gypsiferous groundwater and its desalination brine concentrate: Biomass, water use, and salt “mining” of three Southwestern USA native halophytes

Abstract

In drought affected regions, alternative water sources and salt tolerant crops have become increasingly important. Although there is extensive documentation describing the response of halophytes to NaCl laboratory solutions, limited data exist on their responses to natural brackish groundwater (BGW) and desalination brine concentrate that could be dominated by ions other than Na and Cl. This study investigated the biomass, evapotranspiration (ET), water productivity (WP), and ion uptake responses of three southwestern USA native halophyte species, Atriplex canescens (Pursh) Nutt. (fourwing saltbush), A. lentiformis (Torr.) S. Watson (big saltbush), and Lepidium alyssoides A. Gray var. alyssoides (mesa pepperwort). Six-week-old seedlings were irrigated with a nonsaline control treatment solution [electrical conductivity (EC) of 0.6 dS m-1], CaSO4-dominant BGW (EC ≈ 4 dS m-1), CaSO4-dominant reverse osmosis (RO) concentrate (EC ≈ 8 dS m-1), and counterpart NaCl-dominant solutions (EC ≈ 4 or 8 dS m-1). After 6 wk, BGW and low NaCl solutions increased shoot biomass of . A. lentiformis by ≈ 20% but did not stimulate top growth of A. canescens or L. alyssoides. Increasing salinity had no effect on WP of L. alyssoides, but it increased WP of the Atriplex spp. The combined shoot Na and Cl concentrations reached 7% of dry wt. in L. alyssoides and 9–10% in the Atriplex spp. with no characteristic signs of leaf burn. Conversely, roots were the main sinks for Ca and S, combining for 6–7% of dry wt. and showing the potential to put the main brine solutes to beneficial use. Markedly similar patterns in growth and water use with the NaCl-only solutions and the CaSO4-dominant solutions suggests a primary role of total salinity in these salinity responses, which in turn supports the use of diverse BGW typesnot just NaCl for halophyte production.