Land Application of Wood‐Fired and Combination Boiler Ashes: An Overview

Abstract Ashes from the burning of wood and other plant‐derived materials have been used as soil amendments for centuries. Although historical interest in land application of ashes declined following the advent of commercial fertilizers and alternative liming materials, additional incentives for this beneficial use have arisen in recent years. The first is from rapidly rising landfill costs for disposal of by‐product ashes produced from the paper and electric utility industries. Secondly, the environmental ethic of sustainable management and the concept of recycling have provided incentives to replace nutrients removed from forest and agronomic harvests. Field and greenhouse studies show that wood‐fired boiler ashes can be successfully used as a replacement for agricultural lime with additional nutrient benefits. Ash application on forest land is less common, but Scandinavian studies indicate that ashes can enhance long‐term productivity of some forested sites. The use of ashes alone or combined with other mill residues, fertilizers, or agricultural wastes could prove particularly valuable for sustaining productivity of intensively managed forests over successive rotations. This overview provides an introduction to a subset of papers presented at the “NCASI Symposium on Land Application of Wood‐Fired and Combination Boiler Ashes.”