Root exudates with low C/N ratios accelerate CO2 emissions from paddy soil

Guan Cai, Muhammad Shahbaz, Tida Ge, Yajun Hu, Baozhen Li, Hongzhao Yuan, Yi Wang, Yuhuai Liu, Qiong Liu, Olga Shibistova, Leopold Sauheitl, Jinshui Wu, Georg Guggenberger, Zhenke Zhu

Research output: Contribution to journalArticlepeer-review


Root exudates can significantly modify microbial activity and soil organic matter (SOM) mineralization. However, how root exudates and their C/N stoichiometric ratios control paddy soil C mineralization is poorly understood. This study used a mixture of glucose, oxalic acid, and alanine as root exudate mimics for three C/N stoichiometric ratios (CN6, CN10, and CN80) to explore the underlying mechanisms involved in SOM mineralization. The input of root exudates enhanced CO2 emissions by 1.8–2.3-fold that of soil with only C additions (C-only). Artificial root exudates with low C/N ratios (CN6 and CN10) increased the metabolic quotient (qCO2) by 12% over those with higher stoichiometric ratios (CN80 and C-only), suggesting a relatively high energy demand for microorganisms to acquire organic N from SOM by increasing N-hydrolase production. The increase of stoichiometric ratios of C- to N-hydrolase (β-1,4-glucosidase to β-1,4-N-acetyl glucosaminidase) promoted SOM degradation compared to those involved in organic C- and N- degradation, which had a significant positive correlation with qCO2. The stoichiometric ratios of microbial biomass (MBC/MBN) were positively correlated with C use efficiency, indicating root exudates with higher C/N ratios provide an undersupply of N for microorganisms that trigger the release of N-degrading extracellular enzymes. Our findings showed that the C/N stoichiometry of root exudates controlled SOM mineralization by affecting the specific response of the microbial biomass through the activity of C- and N-releasing extracellular enzymes to adjust the microbial C/N ratio.
Original languageEnglish
Pages (from-to)1193-1203
JournalLand Degradation and Development
Issue number8
Early online date2022 Jan 7
Publication statusPublished - 2022 May

Subject classification (UKÄ)

  • Soil Science


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