The Use of Municipal and Pulp and Paper Sludges to Increase Production in Forestry

Because of their high nutritional content and soil conditioning properties,. municipal and pulp and paper (P&P) sludges-biosolids-can serve as soil amendments for nutritionally deurived or organically soils on forest sites. Studies conducted over the past 20 years at an experimental forest site in Western Washington, USA, have largely confined the potential of biosolids to increase the productivity of many forest lands. These studies clearly demonstrated that application of biosolids at environmentally acceptable rates will result in growth responses for both young seedlings as well as established stands. Municipal biosolids have been applied to a number of different Douglas-fir stands. Young stands applied at 47 Mg ha-1 showed an average of 72%, 14% and 2% height responses for Site Class IV, III and 11, respectively, over a 10 year period. Thinned versus unthinned 55-yeardd Douglas-fir applied with 142 dry Mg ha-l averaged 43% and 48%, respectively, for the 12 year period greater than controls. Average g...