The legacy effect of biochar application on soil nitrous oxide emissions
Shumin Guo, Jie Wu, Zhaoqiang Han, Zhutao Li, Pinshang Xu, Shuwei Liu, Jinyang Wang, Jianwen Zou
Abstract
Abstract Existing studies suggest that biochar application can reduce soil nitrous oxide (N 2 O) emissions, mainly based on short‐term results. However, it remains unclear what the effects (i.e., legacy effects) and underlying mechanisms are on N 2 O emissions after many years of a single application of biochar. Here, we collected intact soil columns from plots without and with biochar application in a subtropical tea plantation 7 years ago for an incubation experiment. We used the N 2 O isotopocule analysis combined with ammonia oxidizer‐specific inhibitors and molecular biology approaches to investigate how the legacy effect of biochar affected soil N 2 O emissions. Results showed that the soil in the presence of biochar had lower N 2 O emissions than the control albeit statistically insignificant. The legacy effect of biochar in decreasing N 2 O emissions may be attributed to the reduced effectiveness of the soil substrate, nitrification and denitrification activities, and the promotion of the further reduction of N 2 O. The legacy effect of biochar reduced the relative contribution of nitrifier denitrification/bacterial denitrification, nitrification‐related N 2 O production, and the relative abundance of several microorganisms involved in the nitrogen cycle. Our global meta‐analysis also showed that the reduction of N 2 O by biochar increased with increasing application rate but diminished and possibly even reversed with increasing experimental time. In conclusion, our findings suggest that the abatement capacity of biochar on soil N 2 O emissions may weaken over time after biochar application, but this remains under further investigation.