Bioextraction of soil boron by tall fescue.

High concentrations of soil B are detrimental to crop productivity in certain arid and semiarid regions of the western United States. Production of tall fescue on B-affected soils may be a viable strategy to reduce and maintain soil B concentrations at nontoxic levels for most agronomic crops. A 2-year field experiment was conducted to study B uptake in tall fescue (Festuca arundinacea) Schreb. cv. Au Triumph grown in soil containing potentially toxic levels of native soil B. The soil B concentrations (water-extractable B greater than 5 mg B liter-1) did not affect the dry matter (DM) yield of tall fescue. Boron concentrations in shoot tissue for both years ranged from 88 to 121 mg B kg-1 DM. whereas in root tissue, concentrations ranged from 50 to 60 mg B kg-1 DM. For both years of the study, soil samples were taken at depth of 0-45 and 45-90 cm at the beginning and end of the designated growing season and analyzed for water-extractable B. Summary data from all cropped plots at the two soil depths indicated that the mean water-extractable B concentrations were reduced by 35% after 2 years in the tall fescue plots, whereas losses of extractable B from bare plots did not exceed 13% for both years. Tall fescue apparently can be used as a component in an overall strategy to lower extractable soil native B levels in irrigated agriculture soils and potentially reduce leaching of B into shallow ground water.