Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/3/1998
Publication Date: N/A
Citation: N/A Interpretive Summary: The world-wide production of coal combustion products has increased markedly which has prompted interest in the use of such products as soil liming materials. In the United States for example, it has been estimated that annual production of combustion products will exceed 150 million Mg by the year 2000 and there is a need to develop use for this material. The two combustion products studied in the work reported were fly ash and bed ash. The alkaline nature of most combustion products has prompted interest in their use in agricultural production as soil liming materials. Recent work has also led to development of technologies for reclamation of metal mining and processing sites that are contaminated by heavy metals. Proper use of these products requires better understanding of the influence of combustion products on soil nitrogen. The work reported studied fate of organic N in soils treated with combustion products. It was found that very high rates of fly ash had only little influence on the fate of this N such rates of bed ash caused substantial decreases in the total N content of water-extracted soil through the mobilization of organic N. Measurements of the changes in various types of organic N in soil permitted characterization of this mobilization. The results of this work will lead to guidelines for use of combustion products without detrimental influence on soil quality.
Technical Abstract: There is growing interest in the use of coal combustion products at agronomic rates based on the liming requirements of agricultural soils and at higher rates in technologies for reclamation of degraded lands. There is concern, however, that excessive or other improper use may have negative impact on soil quality and the environment. To determine the influence of potentially excessive rates of coal combustion products on fate of soil organic N and impacts on soil quality, we studied the effects of two combustion products (fly ash and bed ash) applied at rates of 0, 20, 40, and 80 g/kg soil on the content of organic N in soils incubated for 10, 25, and 60 days. Studies comparing the influence of these products on the organic N content of soil showed that whereas the rates of fly ash had only little influence on the fate of this N, such rates of bed ash caused substantial decreases in the total N content of water-extracted soil through the mobilization of organic N. Measurements of the changes in acid hydrolyzable N components of organic matter in soils treated with high rates of bed ash showed that within the first 10 days of incubation, losses of N in the forms of amino sugar, amino acid, and hydrolyzable ammonium could largely account for losses of total N in bed ash-amended soils. The decreases in the amino acid content of soil organic matter accounted for most of these losses, and such decreases were directly related to increases in soil pH caused by the bed ash amendment.