Root growth and trace element uptake in acid soils treated with coal combustion by-products

Root growth of wheat seedlings (Triticum aestivum) and trace element levels in ryegrass (Lolium multiorum) were determined in acid soils treated with 1.25 to 80 g kg−1 of eight coal combustion by-products: fly ash (FA), bed ash (BA), cyclone ash (CA), limestone injection residue ( LIMB), spray drier residue (SD), scrubber sludge (CS), stabilized scrubber sludge (SS) and gypsum-like material (G). Low application rates of by-products did not inhibit wheat seedling root growth. FA and G did not limit root growth at any application rate while BA, LIMB, SD and CA inhibited root growth at high rates. Ryegrass concentrations of Cu, Zn, Ni, Pb, Cd and Cr were similar in treated and untreated soil. B, Se, As and Mo were increased in ryegrass grown in treated soil, but Se from FA treatments was the only potential food chain risk from a single application of these materials. The G material would seem to be the most benign for land application because it improved root growth without producing elevated trace element levels in plant material or soil solution.