Composting of Forest Nurser y Waste and Nutrient Leaching

The properties of forest nursery waste from the viewpoint of composting are not well known. The objective of the study was to clarify the properties of the forest nursery waste in order to get the thermophilic composting process going on. The composting process and nutrient leaching during composting was also studied. Forest nursery waste including tree seedlings and their growing media (Sphagnum peat), weeds, fallen leaves and grass clippings was composted in 300-litre experimental bins for three months. In the first summer, forest nursery waste was composted with and without horse manure, and during the second summer with and without urea or methylene urea fertilizer. Temperature, volume reduction, pH, water and the organic matter content, nutrient concentrations, water percolation and nutrient leaching were monitored during the composting. Horse manure was the only additive material, which ensured the thermophilic composting process. All additives increased the nitrogen leaching, and horse manure also increased the phosphorus leaching. The results suggest that additive material, such as horse manure, is needed to improve the heating process in forest nursery waste composting. However, the nutrient rich additive material may pose risk for the environment.