BORON AND SELENIUM REMOVAL IN BORON-LADEN SOILS BY 4 SPRINKLER IRRIGATED PLANT-SPECIES

High concentrations of B and Se found in some arid environments are detrimental to sustainable agriculture. Vegetation management may be a remediation strategy designed to reduce soil B and Se concentrations to nontoxic levels. Two separate field experiments were conducted to study B and Se uptake in four different plant species grown in soil containing high concentrations of B (water-extractable B ranging from 1-10 mg kg-1 soil) and Se (total soil Se ranging from 0. 1-1.2 mg kg-1 soil). The four species were Brassica juncea L. Czern and Coss (Indian mustard), Festuca arundinacea Schreb cv. Fawn (tall fescue), Lotus corniculatus L. (birdsfoot trefoil), and Hibiscus cannibinus L. (kenaf). In the 1990 experiment, there were no differences in either tissue B or Se concentrations among the species. The mean tissue concentration was 105 mg B kg-1 dry matter (DM) and 0.75 mg Se kg-1 DM, respectively. In the 1991 experiment, mean shoot tissue concentrations of B ranged from a low of % mg kg-1 DM in tall fescue to a high of 684 mg B kg-1 DM in leaves from kenaf. Indian mustard accumulated the greatest amount of Se (> 1 mg Se kg-1 DM), while the mean tissue concentration among the other three species was 0.36 mg Se kg-1 DM. For both experiments, soil samples were taken prior to planting and after harvest for each species to a depth of 0 to 30 and 30 to 60 cm, and analyzed for water-extractable B and total Se. Summary data from all species indicated that extractable soil B and total Se concentrations were reduced between 0- to 60-cm soil depth by 52 and 48% in 1990, and by 24 and 13% in 1991, respectively. Planting any of the four species tested in B-laden soils may lead to a reduction in both B and Se concentrations in the soil.