Submitted to: Journal of Soil Biology and Biochemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/3/2006
Publication Date: 6/1/2007
Citation: Brunetti, G., Plaza, C., Clapp, C.E., Senesi, N. 2007. Compositional and functional features of humic acids from organic amendments and amended soils in Minnesota. Journal of Soil Biology and Biochemistry. 39:1355-1365. Interpretive Summary: Municipal sewage sludge, manure, solid waste composts, and other organic residues from industrial sources are desirable materials for soil amendments. These materials can better soil quality by improving physical, chemical and biological properties. Many soils will benefit from the application of residues because of the organic matter they contain. The increase in crop yields with applications of amendments greater than 5 tons per acre is related to the supply of nitrogen, phosphorus and potassium where these nutrient elements are low in the soils. The humic substances (humic and fulvic acids), isolated from these organic amendments were shown to provide proteins, sulfur and other organic residues as part of the native soil organic matter. The impact of these results can be made by extension specialists and others with environmental interests to provide information to farmers and researchers who benefit from application of organic wastes to land.
Technical Abstract: The use of organic amendments requires an adequate control of the chemical quality of their humic acid (HA)-like fractions and of the effects that these materials may have on the status, quality, chemistry and functions of native soil HAs. In this work, the compositional, functional and structural properties of the HA-like fractions isolated from a liquid swine manure (LSM), a municipal sewage sludge (SS), and two municipal solid waste composts (MSWCs) were evaluated in comparison to those of HAs isolated from three unamended soils and from the corresponding soils amended with LSW, SS, and MSWC at various rates in three field plot experiments conducted in Minnesota, USA. With respect to the unamended soil HAs, the HA-like fractions of the three amendments featured a greater aliphatic character, a marked presence of proteinaceous, S-containing and polysaccharides-like structures, an extended molecular heterogeneity, small organic free radical contents and small degree of humification. The MSWC-HAs featured a larger humification degree than LSM-HA and SS-HA. The three amendments affected in different ways and at various extent the compositional, structural and functional properties of soil HAs in dependence on the nature, origin and application rate of the amendment. In general, the data obtained suggested that proteinaceous, S-containing and aliphatic structures contained in HA-like fractions of organic amendments were partially incorporated into native soil HAs.