Coal Bottom Ash as a Component of Floriculture Root Media

Abstract

Our research emphasis has been on utilization of industrial by-products as components of plant root substrates. Coal bottom ash (CBA) collects at the base of furnaces of coal-fired power plants, in contrast to fly ash, which is removed from stack fumes by electrostatic precipitators. A majority of CBA is disposed in landfills. Its low cost and availability in large quantities (in 1994, >14 million tons were produced in the United States, of which only ≈5 million tons were marketed) recommend it for trial as a component of root media, which currently contain far more expensive ingredients. CBA tends to increase pH and EC and decrease water and air capacities of root media. When used as a root medium in a closed loop nutriculture system, it caused an increase in Ca, K, and Na in the nutrient solution. Crops grown in CBA root media include pot and cut chrysanthemums, roses, rhododendrons, poinsettias, Easter lilies, peperomia, zonal and ivy geraniums, impatiens, New Guinea impatiens, and hydrangeas. In general, growth parameters such as plant dry weight and flower number tended to decline at media CBA levels of 75% or more. At CBA levels of 50% or less, these parameters tended to equal or surpass those of plants in control (0% CBA) media.