Effects of nitrogen addition on carbonate-derived CO 2 emission after biochar addition

• Published in: Soil Ecology Letters 2023, Vol.5 (4), p.220169
• Main Authors: Sun, Zhaoan, Hao, Tianxiang, Zhu, Biao
• Format: Article
• Language: English
• Subjects: 13C isotope; biochar; soil CO 2 emission; soil inorganic carbon; soil organic carbon; three-source partitioning
• ISSN: 2662-2289; 2662-2297
• DOI: 10.1007/s42832-022-0169-8

● We studied the effect of nitrogen and biochar on CO 2 emission from SOC and SIC. ● Nitrogen increased SIC-derived CO 2 by 41% but decreased SOC-derived CO 2 by 20%. ● Biochar reduced total soil-derived CO 2 by neutralizing nitrogen-induced acidity. ● We proposed a method for 3- or 4-source partitioning CO 2 emission from calcareous soils. Biochar addition generally increases the alkalinity regeneration to resist soil acidification driven by nitrogen (N) fertilization. Calcareous soils contain soil organic carbon (SOC) and inorganic C (SIC). Owing to technical limitations in three-source partitioning CO 2, how biochar addition affects SOC- and SIC-derived CO 2 emission has not been clarified yet. Therefore, we conducted a 70-day incubation experiment of ammonium-N and maize-straw-derived biochar additions to investigate the N plus biochar impacts on SOC- and SIC-derived CO 2 emission. Over the 70-day incubation, we found that the N-only addition increased the SIC-derived CO 2 emission by approximately 41% compared with the control, but decreased the SOC-derived CO 2 emission by approximately 20%. This suggests that the distinct responses of SIC- and SOC-derived CO 2 emission to N-only addition come from N-induced acidification and preferential substrate (N) utilization of soil microorganisms, respectively. Compared with N-only addition, N plus biochar addition decreased the SIC-derived CO 2 emission by 17%−20% during the first 20 days of incubation, but increased it by 54% during the next 50 days. This result suggested that biochar addition reduced the SIC-derived CO 2 emission likely due to the alkalization capacity of biochar exceeding the acidification capacity of ammonium-N in the short term, but it may increase the SIC-derived CO 2 emission induced by the weak acidity produced from biochar mineralization in the long term. This study is helpful to improve the quantification of CO 2 emission from calcareous soils.