|VAN PATTEN, CHRISTA|
Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 10/21/2001
Publication Date: N/A
Technical Abstract: Soil samples were taken from a Rosemount, MN long-term field experiment where 40 at-% N-15 was applied for 15 yr under N-tillage-residue management treatments. The plots were cropped to corn (Zea mays L.) for 15 yr, followed by 5 yr of soybean [Glycine max (L.) merr.] with no N applied, and then 1 yr of corn before sampling. The samples represented combinations of ftill and no-till, with residue-removed or residue-harvested, at 2 g N m-2 as ammonium sulfate. Humic acids (HAs) were extracted using a modified IHSS method, and isolated by membrane-filtration, precipitated, dialyzed, and freeze-dried. Elemental analyses showed minor differences between HAs, with residue-returned samples having higher C and N values. Differences were also noted between residue-removed and residue-returned treatments, for carbohydrates, amino acids and acidity components. FTIR, fluorescence, and CPMAS 13C-NMR spectra provided valuable characterization and compositional information.