Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 11/5/2000
Publication Date: N/A
Technical Abstract: Soil samples from a long-term experiment on tillage and nitrogen management under continuous corn (13 yr) and later cropped to soybean (6 yr) were extracted by a modified IHSS procedure to isolate the humic substances as related to the different management systems. Corresponding humic fractions were also isolated from an adjacent N-15-labeled long-term experiment. The ehumic acids (HAs) were purified by membrane-filtration, reprecipitated, dialyzed, and freeze-dried. Elemental analysis data showed minor differences between HAs, with residue-return samples having higher C and N values. Differences were also noted between residue removed- and residue- return treatments for carbohydrates, amino acids and acidity contents. FTIR, fluorescence, and CPMAS 13-C-NMR spectra provided valuable characterization and compositional information.