GROWTH AND TRACE-ELEMENT CONCENTRATIONS OF 5 PLANT-SPECIES GROWN IN AHIGHLY SALINE SOIL

Kesterson Reservoir and other impoundments in the San Joaquin Valley, California, have received large volumes of saline irrigation drainage water that is enriched with trace elements, including As, B, Mo, Se, U , and V. When these ponds are allowed to dry and revert to terrestrial ecosystems, careful soil water and vegetation management may be neede d to prevent toxicological hazards to wildlife and/or livestock. We co nducted a 248-d column study in the greenhouse using a soil from Keste rson to assess the growth of salt- and B-tolerant genotypes, and to de termine the uptake of As, B, Mo, Se, U, and V by these genotypes. Elec trical conductivity decreased with soil depth, from 14 to 5 dS m-1, wi th B, Mo, Se, and U concentrations paralleling the soil salinity, wher eas As and V were higher in the subsoil. Three grasses, alkali sacaton [Sporobolus airoides (Torr.) Torr.], tall wheatgrass [Elytrigia ponti ca (Podp.) Holub], Indian ricegrass [Oryzopsis hymenoides (Roem & Schu lt.)], and two Sc-accumulators, Astragalus bisulcatus (Hook.) and A. r acemosus Pursh., were successfully established after a preplanting lea ching treatment to reduce salts in the seed zone. Three cuttings of al kali sacaton and tall wheatgrass resulted in total shoot yields of 11. 1 and 7.6 g per column, respectively, but only 0.8 for a single cuttin g to the less salt- and B-tolerant Indian ricegrass. The slower-growin g A. bisulcatus and A. racemosus yielded 3.8 and 4.4 g per column, res pectively. Shoot concentrations of As, U, and V were low (<3 mg kg-1) in all genotypes, and do not seem to pose food-chain transfer hazards at this site. Molybdenum and Se shoot concentrations of all genotypes exceeded the upper safe limits for consumption by ruminants, and shoot B concentrations were also high (>60 mg kg-1). Despite high soil solu tion SO, concentrations, both Astragalus species accumulated Se to hig h concentrations in the shoots (ca. 650 mg kg-1), and shoot harvest re moved the equivalent of 2 to 3.5 kg Se ha-1. Growth of these Se-accumu lating species shows promise as a means of direct removal of Se from S e-contaminated sites and could become a component of effective remedia tion strategies.