15N-amino sugar stable isotope probing (15N-SIP) to trace the assimilation of fertiliser-N by soil bacterial and fungal communities

Publication date: Available online 17 September 2019Source: Soil Biology and BiochemistryAuthor(s): Michaela K. Reay, Alice F. Charteris, Davey L. Jones, Richard P. EvershedAbstractAlthough amino sugars represent a major component of soil organic nitrogen (ON), the assimilation of nitrate (NO3− ) and ammonium (NH4+) into amino sugars (AS) by soil bacteria and fungi represents a neglected aspect of the global N cycle. A deeper knowledge of AS responses to N fertiliser addition may help enhance N use efficiency (NUE) within agricultural systems. Our aim was to extend a sensitive compound-specific 15N-stable isotope probing (SIP) approach developed for amino acids to investigate the immobilization of inorganic N into a range of amino sugars (muramic acid, glucosamine, galactosamine, mannosamine). Laboratory incubations using 15N-ammonium and 15N-nitrate applied at agriculturally relevant rates (190 and 100 kg N ha−1 for 15NH4+ and 15NO3−, respectively) were carried out to obtain quantitative measures of N-assimilation into the AS pool of a grassland soil over a 32-d period. Using gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) we found that δ15N values for individual AS reflected differences in routing of the applied ammonium and nitrate. The contrasting N-assimilation dynamics of bacterial and fungal communities were demonstrated through determinations of percentage 15N incorporation into diagnostic AS. N-assimilation dynamics of the bacterial c...
Source: Soil Biology and Biochemistry - Category: Biology Source Type: research