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Title: FLY-ASH ORGANIC BYPRODUCT MIXTURE AS SOIL AMENDMENTS

Author
item SAJWAN, K - SAVANNAH STATE UNIV
item PARAMASIVAM, S - SAVANNAH STATE UNIV
item Alva, Ashok
item SAHI, S - WESTERN KENTUCKY UNIV

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 2/1/2006
Publication Date: 9/15/2006
Citation: Sajwan, K.S., Paramasivam, S., Alva, A.K., Sahi, S.V. 2006. Fly-ash organic byproduct mixture as soil amendments. In: Twardowsaka, I., H.E. Allen, and M.H. Haggblom (ed.) Viable Methods of Soil and Water Pollution Monitoring, Protection, and Remediation. NATO Earth and Environmental Sciences Book Series, Springer Publishers, Netherlands. Pg 387-399.

Interpretive Summary: Coal combustion byproducts (CCBP), such as fly ash (FA) or flue gas desulfurization gypsum (FGDG), and animal waste or water treatment residuals, such as sewage sludge (SS) or animal manure, can be used as amendments to agricultural soils to enhance physical, chemical, and biological properties. FA is alkaline, thus could raise the soil pH and contains no nitrogen (N) or phosphorus (P). SS is acidic and contains appreciable levels of N and P. Therefore, combination of FA and SS can provide all three major nutrients such as N, P, and potassium (K) with minimum changes in the soil pH. In this study, application of FA:SS mixture to a sandy soil at either 1:4, 2:4, 3:4, or 4:4 ratios at 124 to 247 tonnes/hectare rates, demonstrated beneficial affects on biomass production of sorghum sudangrass compared with that in unamended soil. The biomass production decreased as the amendment rates were further increased in the range of 371 to 988 tonnes/ha. In a parallel study, the biomass production of collard green plants showed significant positive response to application of 24.7 and 49.4 tonnes/ha rates of 1:1 ratio SS:FA mixture. The above response was similar regardless of using a domestic or industrial source of SS. In a leaching column study, leaching of most metals was lower with application of 148.2 tonnes/hectare of FA + SS mixture to a sandy soil compared with the combined quantities of metals leached from application of 74.1 tonnes/hectare each of FA and SS separately. Amending the soil with a mixture of FA and SS may provide a pH balance that can minimize leaching of metals compared with application of either FA or SS separately.

Technical Abstract: We hypothesized that using a mixture of fly ash (FA) and sewage sludge (SS) as an amendment for agricultural soils could prove beneficial for plant growth and production as well as increased retention of nutrients in the soil compared with using either source individually. This paper summarizes greenhouse studies conducted to evaluate the effect of FA and organic waste mixtures on growth and elemental uptake by Sorghum Sudangrass (Sorghum vulgaris) and Collard Greens (Brassica olerecea). In addition, the results of a leaching study are also discussed. Results of a greenhouse study demonstrated that plant establishment, subsequent growth, and biomass production of Sorghum sudangrass were significantly greater with application of 124 or 247 Mg ha-1 of FA+SS amendment to a sandy soil compared with that with no amendment, irrespective of different ratios of FA:SS. Further increment in the rate of amendment in the range of 371 to 988 Mg ha-1 decreased the biomass production. For collard greens, the biomass increased with application of 24.7 or 49.4 Mg ha-1 of SS+FA (1:1 ratio) to a sandy soil compared with that with no amendment. The biomass production slightly decreased with further increment in rate of amendment in the range of 98.8 to 148.3 Mg ha-1. Results of a parallel leaching column study showed that soil pH response to application of these amendments in a mixture vs. as a single source could influence the leaching of metals and micronutrients. The quantities of cumulative leaching (in 3.5 pore volumes of leachate) of micronutrients and metals from the soil amended with 148.2 Mg ha-1 of 1:1 FA+SS mixture were substantially lower than the combined quantities of the respective micronutrients and metals leached from soil columns, which were amended with 74.1 Mg ha-1 each of FA and SS separately. This clearly showed the benefit of using FA+SS mixture rather than using them separately. The concentration of most metals in the leachate following application of low to moderate rates of FA+SS mixtures generally did not exceed the USEPA stipulated maximum contaminant level for most metals.