FEASIBLE AND COST EFFECTIVE FOREST LAND APPLICATION OF MUNICIPAL SLUMiE

Dale G. Brockway N Michigan, 199 municipal and numerous industrial wastewater treatment facilities annually generate 222,750 dry tons of sludge, most of which is recycled on farmland. Substantial potential exists, however, to increase application on forest land in the northern two-thirds of the state (Brockway and Nguyen 1986). Although sludge application on agricultural land has received more study, forest land offers numerous unique advantages (Smith and Evans 1977). The nonedible nature of forest crops generally diminishes the risk of human exposure to elements which may be hazardous in the food chain. While adapted to low ambient nutrient levels in forest soils, native plants respond to sludge application with significant nutrient and biomass increases (Brockway 1983, Zasoski et al. 1983, Wells et al. 1984, Berry 1987). The long-term accumulation of biomass affords substantial storage capacity for certain elements during a crop rotation and harvesting offers a means of removing elements from treated sites. Forest soils are generally porous, resulting in minimal surface runoff of applied ,nutrients, .and often nutritionally impoverished, providing opportunity to substantially increase soil organic matter and nutrient levels with sludge additions. Forest sites are also commonly located away from large population centers and are used for dispersed recreational activities, r&imi&g the opportunity for human contact with recently applied sludge. In 1975, USDA Forest Service scientists initiated a series of small plot studies in the forests of northern Michigan to assess the growth and environmental effects of various sludge types applied at widely ranging rates (Urie et al. 1978, Brockway 1979). Results of these studies were used in 1980 to prescribe sludge application rates for an operational scale research-demonstration jointiy initiated by the U.S. Environmental Protection Agency, Michigan Department of Natural Resources and Michigan State University Department of Forestry and Department of Fisheries and Wildlife. The objective of this project was to further examine the environmental effects, sociological dynamics and operational feasibility of large scale forest land application programs and develop regulatory guidance for future use.