Growth and Heavy Metal Accumulation in Pine Seedlings Grown with Sewage Sludge

Abstract

AbstractLoblolly pine seedlings were grown in microplots amended with 34 or 68 Mg ha−1 of one of five sewage sludges; (i) old sludge from Athens, GA, (ii) fresh sludge from Athens, GA, and sludges of undetermined age (ii) from Aikens, SC, (iv) from Newberry, FL, and (v) from Chicago, IL. Newberry sludge and fresh Athens sludge supported growth comparable to the inorganic fertilizer control. Seedlings grown with Chicago sludge grew well at the 68 Mg ha−1 rate (23.6 cm in height, 4.2 cm in root collar diameter and weighing 8.3 g) but were not as large as those grown with fertilizer (22.8 cm in height, 5.3 cm in root collar diameter and weighing 12.2 g). Seedlings grown with old Athens or Aiken sludge did not grow well and most of them were not of plantable size (i.e. 15 cm in height and 3.5 mm in root collar diameter). Pisolithus tinctorius did not form ectomycorrhizae on seedlings grown with the sludges as well as on seedlings grown with fertilizer (in most cases < 23% of short roots compared to 63% for controls). Thelephora terrestris formed ectomycorrhizae as readily on seedlings grown with the sludges as those grown with fertilizer when inoculation with the fungus was artificial; natural ectomycorrhizae, however, did not form as readily with some sludges as with fertilizer. When grown with Chicago sludge, roots, stems, and needles of seedlings had significantly more cadmium (two‐ to fourfold) than seedlings grown with other sludges. Poor growth of seedlings grown in old Athens sludge is assumed to be due to deficiencies of macronutrients, since fresh Athens sludge supported good growth. With Aiken sludge and to a lesser degree, Chicago sludge, toxicity of heavy metals is considered to be a possible factor contributing to poor seedling growth.