Microbial activity differentially regulates the vertical mobility of nitrogen compounds in soil |
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| Institution: | 1. School of Geography Sciences, Nanjing Normal University, Nanjing 210023, China;2. Northeast Institute of Geography and Agroecology, Chinese Academy of Science, Changchun 130102, China;3. Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing 210023, China;4. State Key Laboratory Cultivation Base of Geographical Environment Evolution (Jiangsu Province), Nanjing 210023, China;5. Key Laboratory of Virtual Geographic Environment (Nanjing Normal University), Ministry of Education, Nanjing 210023, China;6. Department of Plant Ecology (IFZ), Justus-Liebig University Giessen, Heinrich-Buff-Ring 26, 35392 Giessen, Germany;7. School of Biology and Environmental Science, University College Dublin, Ireland |
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| Abstract: | Alongside nitrate, dissolved organic nitrogen (DON) represents a significant N loss pathway in many agroecosystems. To better understand the factors controlling DON leaching in soil we followed the vertical movement of 15N-labeled NO3?, NH4+, alanine and trialanine in packed soil columns in response to a simulated rainfall event. We show that in autoclaved (sterile) soil where sorption is assumed to be the dominant regulating factor, leaching followed the series NO3? > trialanine > alanine > NH4+. In the non-sterile packed soil columns, the rapid rate of NO3? leaching was unaffected whilst the movement of the amino acid, peptide and NH4+ was almost completely prevented due to microbial immobilization. Our results support the view that (1) DON loss from agricultural soils occurs mainly in the form of recalcitrant compounds (e.g. humic DON) rather than in the form of labile low MW DON (e.g. oligopeptides and amino acids), and (2) that although nitrate was bioavailable, it was not a preferred N form for the C-limited microbial biomass. |
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