Relating Research Results to Sludge Guidelines for Michigan's Forests
Guidelines for application of wastewater sludge to forest land in Michigan were developed by the Department of Natural Resources from research studies on small plots and large-scale demonstration sites. Growth response and groundwater quality data provided a basis for estimating appropriate application rates, selecting suitable application sites, and developing proper application procedures. Balancing nutrient additions with the assimilation capacity of each forest ecosystem was found to enhance site productivity while minimizing nutrientenrichment of groundwater. This principle, referred to as the periodic agronomic rate, is similar to the already widely accepted annual agronomic rate currently in place as policy for sludge application on cropland. The periodic agronomic rate, however, recognizes the unique nutrient cycling and long-term storage potential of aggrading forests. Sludge nutrient application rates and operational procedures reflect the need for a conservative approach in protecting the environment and public health when implementing regulatory programs that employ new technology.