Submitted to: International Humic Substances Society Conference
Publication Type: Abstract Only
Publication Acceptance Date: 7/1/1998
Publication Date: N/A
Technical Abstract: Fulvic acids (FAs) were isolated from three different soils amended with various rates of two different composts, an animal manure, a municipal sludge, and a sweet corn residue. The FAs were also isolated from the corresponding unamended (control) soils and from each amendment used. Significant differences are observed between FAs isolated from amended and unamended soils and especially between FAs isolated from soils and from amendments. The FA yield is greater for the amended soils than the unamended ones, and is directly related to the type and rate of amendment. The elemental composition of soil FAs is significantly different from that of FA-like substances isolated from the amendments. In particular, FAs from composts and sludge are characterized by much higher N and S contents and lower C/N and C/H ratios than those from soil FAs. Manure FA shows lower N and O contents and C/H and O/C ratios, and higher C, H and S contents and C/N ratio, with respect to soil FAs. Fluorescence emission, excitation, an synchronous spectra of FAs isolated from amendments are characterized by main peaks positioned at lower wavelengths than those of FAs isolated from any soil, irrespective of the amendment type and/or rate. The FTIR spectra of FAs extracted from the various amendments are typical of low MW fractions of soil FAs. In general, FT-IR spectra of amended soil FAs show only slight differences with respect to unamended soil FAs, which are mainly related to absorptions of polysaccharides, aliphatic C-H, and aromatic C=C bonds. These results suggest that organic amendments markedly affect the chemical composition and functionalities of soil FAs, with an increase of polysaccharide and carbonyl functions and a slight increase of aromaticity.