AUTHOR=Wei Jing , Reichel Rüdiger , Islam Muhammad Saiful , Wissel Holger , Amelung Wulf , Brüggemann Nicolas 

TITLE=Chemical Composition of High Organic Carbon Soil Amendments Affects Fertilizer-Derived N2O Emission and Nitrogen Immobilization in an Oxic Sandy Loam

JOURNAL=Frontiers in Environmental Science

VOLUME=8

YEAR=2020

URL=https://www.frontiersin.org/journals/environmental-science/articles/10.3389/fenvs.2020.00015

DOI=10.3389/fenvs.2020.00015

ISSN=2296-665X

ABSTRACT=<p>Nitrous oxide (N<sub>2</sub>O) emission is a negative side effect of modern agriculture and a serious issue for global climate change. The combined application of nitrogen (N) fertilizer and high organic carbon soil amendments (HCA) has been regarded as an alternative to promote fertilizer-related N immobilization and enhance nitrogen use efficiency. The effect of HCA on N<sub>2</sub>O emission and N immobilization highly depends on its chemical composition, as it controls carbon (C) supply to soil microbes and reactivity of lignin-derived phenols to fertilizer-derived N species. Here we present a 127-d laboratory incubation study to explore the N<sub>2</sub>O emission and N immobilization after combined application of N fertilizer and HCA (wheat straw, spruce sawdust, and commercial alkali lignin) differing in their chemical composition. The <sup>15</sup>N labeling technique was used to trace the transformation of fertilizer-N in ammonium (NH<sub>4</sub><sup>+</sup>), nitrate (NO<sub>3</sub><sup>–</sup>), soil organic nitrogen (SON), and N<sub>2</sub>O. The amendment of wheat straw and spruce sawdust greatly promoted N immobilization and N<sub>2</sub>O emission, while lignin amendment enhanced the immobilization of fertilizer N. The chemical composition of HCA explained 26% of the total variance of fertilizer-derived N<sub>2</sub>O emission and N retention via soil microbial biomass, composition of lignin-derived phenols, and nitrification. The holocellulose/lignin ratio of HCA could be used as an indicator for predicting HCA decomposition, microbial N immobilization and N<sub>2</sub>O emission. In addition, the composition of lignin-derived phenols was affected by HCA amendment and significantly related to N<sub>2</sub>O emission and N retention. The varying chemical composition of HCA could thus be a promising tool for controlling N<sub>2</sub>O emission and N immobilization in environment-friendly and climate-smart agriculture.</p>