Molecular weight separation of hot-water extractable soil organic matter using high-performance size exclusion chromatography with chemiluminescent nitrogen detection

Abstract

To characterize soil organic nitrogen (N), we applied high-performance size exclusion chromatography (HPSEC) and chemiluminescent nitrogen detection (CLND) to the molecular weight separation of hot-water extractable organic matter (HWEOM) from soils that had been amended with or without plant residue compost applied at a rate of 2 kg m−2 y−1 for 25 years. The N chromatogram of the HWEOM showed that the HWEOM containing N had molecular weights ranging from 0.1 to 100 kDa. The N chromatograms of HWEOM from soils without compost differed among four soils (Cumulic Andosol, Low-humic Andosol, Gray Lowland soil, and Yellow soil). The N intensities in the HWEOM chromatograms were larger in the soils with compost amended than in those without compost over the whole range of molecular weights. These results demonstrate that HPSEC/CLND is a useful tool to investigate the structure and dynamics of water soluble organic N in soil.