ARS | Publication request: FT-IR and C-13 NMR analysis of soil humic fractions from a long term cropping systems study

Submitted to: Humic Science and Technology Conference
Publication Type: Abstract Only
Publication Acceptance Date: February 26, 2010
Publication Date: March 17, 2010
Citation: He, Z., Mao, J., Tazisong, I., Senwo, Z. 2010. FT-IR and C-13 NMR analysis of soil humic fractions from a long term cropping systems study [abstract]. Humic Science and Technology Conference. p. 58.

Technical Abstract: Increased knowledge of humic fractions is important due to its involvement in many soil ecosystem processes. Soil humic acid (HA) and fulvic acid (FA) from a nine-year agroecosystem study with different tillage, cropping system, and N source treatments were characterized using FT-IR andsolid-state C-13 NMR spectroscopy. Differences in FT-IR band intensities were observed among those samples. Generally, the impacts of management practices were reflected by changes in band intensity in the 3000-2900 cm-1, (C-H of the aliphatic group), 1624 cm-1(aromatic C=C, COO-, H-bonded C=O of conjugated ketones), 1212-1233 cm-1 (C-O and O-H of carboxyls, phenols, and aromatic ethers), and 1074-1084 cm-1 (alcoholic and polysaccharide C-O, SiO2, and P compounds) regions. Correlation analysis indicated that NMR peakintensity at 161-190 ppm (COO and N-C=O) is highly positively correlated with peak intensity at 145-162 ppm (aromatic C-O), but negatively correlated with peak intensities at 60-96 ppm (carbohydrate ), 50-60 ppm (NCH and OCH3), and 0-50 ppm (nonpolar alkyl). The peak intensities at 60-96 ppm (carbohydrate) are also negatively correlated with peak intensities at 145-162 ppm (aromatic C-O) and 108-145 ppm (aromatic C). These observations suggest that COO and N-C=O groups are more associated with the aromatic part of these humic fractions. However, peak intensities at 90-220 ppm (ketone, quinone, or aldehyde C) were not correlated with any other peak intensity, indicating this type of functional group could be associated with either aromatic or aliphatic groups of these soil humic fractions.