The potential of lime-stabilized and chemically-fixed municipal sewage sludges for land application as lime or nitrogen sources

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1986
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Virginia Polytechnic Institute and State University
Abstract

Lime-stabilized and chemically-fixed sludges have been inadequately characterized for utilization as amendments to acid soils. Laboratory incubation studies were employed to evaluate calcium carbonate equivalence (CCE) and nitrogen (N) mineralization rates of these sludges when applied to three acid Typic Hapludults from Virginia. Greenhouse studies were conducted to evaluate the effect of increasing sludge application rates on growth of corn. The CCE of the lime-stabilized and chemically-fixed sludges were 30. 9 and 58.1%, respectively. Application of sludges to soils resulted in rapid neutralization of soil acidity. Added organic-N was mineralized at an average rate of 32% in surface soils. Based on N mineralization, application rates of lime-stabilized and chemically-fixed sludges will be limited by CCE for most soils. Corn yields on the Glenelg and Tatum soils were improved by addition of the sludges and remained within 95% of maximum at 118 and 160%, respectively, of the rate predicted to raise soil pH to 6.5. Zinc deficiencies were induced at the highest sludge application rates. Corn yields were higher when soils were amended with lime-stabilized or chemically-fixed sludges than when amended with CaC03 because the sludges contained Zn and other nutrients. Lime-stabilized and chemically-fixed sludges are good sources of lime which will supply N at the rate of approximately 32% of applied organic-N but overapplication of these sludges to meet the N needs of corn will probably result in Zn deficiency on all but the most acid soils.

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