BIOEXTRACTION OF SELENIUM BY FORAGE AND SELECTED FIELD LEGUME SPECIESIN SELENIUM-LADEN SOILS UNDER MINIMAL FIELD MANAGEMENT CONDITIONS

A forage plant, tall fescue (Festuca arundinacea), and a selected fiel d legume species, sour clover (Melilotus indica), were examined for th eir selenium (Se) bioextraction abilities in Se-laden soils under mini mal management conditions. Natural vegetations in a 2-acre plot adjace nt to the forage plots were also studied for Se accumulation compariso ns. During the dry season, in the fall of 1994, the field plots were e ither irrigated weekly or without irrigation. No fertilization and wee d control were applied. The plants were harvested in May 1995. There w ere considerable differences in the ability of Se uptake between the f orage and the legume species and among the naturally established plant species; the amount of Se accumulated per land area was largely depen dent on their respective biomass production. Comparing Se concentratio n between preplant and postharvest, there was a detectable reduction i n the soil selenate, selenite, and water-extractable organic Se in the tall fescue and melilotus plots. The held irrigation provided more fa vorable conditions for bioextractions and dissipation of Se by the pla nts. However, the available soil Se only accounts for less than 10% of the total soil Se and no detectable reduction of total soil Se was fo und. This may be due to the large inventory and variation of Se concen trations in the held soils and therefore obscured the detectable diffe rences. For practical considerations, the forage plants can be repeate dly harvested and used for rangelands of Se deficiency currently seen in some northern California counties. (C) 1996 Academic Press, Inc.