Nitrous oxide emissions in Fe-modified biochar amended paddy soil are controlled by autotrophic nitrification
Yihe Zhang, Mengyuan Huang, Haojie Ren, Yue Shi, Siyan Qian, Yuxin Wang, Jinbo Zhang, Christoph Müller, Shuqing Li, Jordi Sardans, Josep Peñuelas, Jianwen Zou
Abstract
We investigated the potential of ferric iron-modified biochar to lessen autotrophic nitrification and lower nitrous oxide (N2O) emissions in paddy soils. A 15N tracing incubation was conducted to investigate the changes in soil gross nitrogen (N) transformations under various biochar amendments (control, unmodified biochar, and Fe-modified biochar). Acetylene and 1-octyne were used to assess the relative contributions of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) to N2O emission from paddy soil. The Fe-modified biochar increased the rate of NH4+ immobilization by 26 % and 383 % compared to the control and unmodified biochar treatments, respectively. The gross rate of autotrophic nitrification was reduced to 5.43 μg N g−1 d−1 in the Fe-modified biochar treatment, compared to 6.74 μg N g−1 d−1 in the control treatment and 9.38 μg N g−1 d−1 in the unmodified biochar treatment. Soil pH had varying effects on N2O emissions involving AOB and AOA. The N2O yields of AOA were more sensitive to Fe-modified biochar applications. AOB, specifically the Nitrosopira-AOB genus, dominated N2O production in all treatments. Overall, this study suggests that Fe-modified biochar holds greater potential than unmodified biochar in reducing N2O emissions from paddy soils by stimulating NH4+ adsorption, restraining autotrophic nitrification rates, and AOB-dominant N2O production pathways.