Kinetics of amino sugar formation from organic residues of different quality

Amino sugars are key compounds of microbial cell walls, which have been widely used as biomarker of microbial residues to investigate soil microbial communities and organic residue cycling processes. However, the formation dynamics of amino sugar is not well understood. In this study, two agricultural Luvisols under distinct tillage managements were amended with uniformly ¹³C-labeled wheat residues of different quality (grain, leaf and root). The isotopic composition of individual amino sugars and CO₂ emission were measured over a 21-day incubation period using liquid chromatography–isotope ratio mass spectrometry (LC–IRMS) and trace gas IRMS. Results showed that, the amount of residue derived amino sugars increased exponentially and reached a maximum within days after residue addition. Glucosamine and galactosamine followed different formation kinetics. The maxima of residue derived amino sugars formation ranged from 14 nmol g⁻¹ dry soil for galactosamine (0.8% of the original concentration) to 319 nmol g⁻¹ dry soil for glucosamine (11% of the original concentration). Mean production times of residue derived amino sugars ranged from 2.1 to 9.3 days for glucosamine and galactosamine, respectively. In general, larger amounts of amino sugars were formed at a higher rate with increasing plant residue quality. The microbial community of the no-till soil was better adapted to assimilate low quality plant residues (i.e. leaf and root). All together, the formation dynamics of microbial cell wall components was component-specific and determined by residue quality and soil microbial community.