Effect of Irrigation Water Salinity and Sodicity and Water Table Position on Water Table Chemistry Beneath Atriplex lentiformis and Hordeum marinum

Abstract

Coal bed methane (CBM) extraction in Montana and Wyoming's Powder River Basin (PRB) produces large quantities of modestly saline-sodic water. Such water can cause dispersion of clays, degradation of soil structure, and osmotic stress in plants. This study assessed effects of irrigation water quality and water table position on water chemistry of closed columns, simulating a perched or a relatively shallow water table. The experiment presents an assessment of potential salt loading in areas where shallow or perched water tables prevent leaching or where artificial drainage is not possible. Water tables were established in sand filled PVC columns (0.20 m diameter × .005 m wall thickness × 1.22 m tall) at 0.38, 0.76, and 1.14 m below the surface, after which columns were planted to one of three species, two halophytic Atriplex spp. and Hordeum marinum Huds. (maritime barley), a glycophyte. Results for the two Atriplex ssp. did not differ significantly, and therefore, only results from Atriplex lentiformis (Torr.) S. Wats. (big saltbush) and H. marinum are presented in this article. Columns were irrigated for 224 d; irrigation water supplied every 7 d was equal to evapotranspiration (ET) + 100 mL. This amount replaced the water lost to ET between sampling, plus the volume of the water sample. Irrigation water representing one of two irrigation sources was used: Powder River (PR) [electrolytic conductivity (EC) = 0.19 Sm−1, sodium adsorption ratio (SAR) = 3.5] or CBM water (EC = 0.35 Sm−1, SAR = 10.5). Irrespective of species, continuous irrigation with CBM and PR water led to salt loading over time, the extent of which was proportional to the salinity and sodicity of applied water. Water in columns planted to A. lentiformis with water tables maintained at 0.38 m depth consistently had significantly greater EC and SAR values than those with 0.76 and 1.14 m water table positions. Elevated EC and SAR values most likely reflect the shallow rooted nature of A. lentiformis, which resulted in enhanced ET with the water table close to the soil surface. H. marinum's deep rooted nature and subsequent ability to utilize water from a variety of depths did not produce any significant differences in EC and SAR as a result of varying water table positions.