Long-Term Effect of Coal Fly Ash Application on Soil Total Nitrogen and Organic Carbon Concentrations

Abstract

The study was performed on the basis of a field experiment established in 1984. Coal fly ash was applied at a rate of 0–800 t/ha with organic fertilizers — farmyard manure, straw, and tree bark. In the first years of research, only traditional crops were grown in trial plots. Since 1992, the field was used as permanent grassland, and no mineral amendments were applied. Nineteen years after fly ash application, soil samples were collected for analyses, which included determination of organic C and total N levels. It was found that coal fly ash applied in 1984 permanently changed the properties of the soil. Despite passage of a long period since their application, significant differences were still observed among the combinations, especially in the organic carbon content of the soil plough layer. The organic carbon concentration was also permanently affected by organic fertilizers. Tree bark had the most beneficial effect on the soil levels of organic carbon. The experimental factors had a less powerful influence on the total nitrogen concentration. The C:N ratio of the soil showed that coal fly ash considerably modified nitrogen values. This indicates a long-term effect of coal fly ash on nutrient immobilization and mineralization in the soil.