Jiangsu Key Laboratory of Low Carbon Agriculture and GHGs Mitigation,College of Resources and Environmental Sciences,Nanjing Agricultural University
National Natural Science Foundation of China (No. 41977078) and Postgraduate Research & Practice Innovation Program of Jiangsu Province, China (KYCX21_0618)
作为一种重要的土壤调节剂，生物质炭在固碳减排，尤其在氧化亚氮(N2O)减排方面的作用日益突出。本研究通过田间定位试验，分析稻麦轮作体系新鲜和田间不同时间老化生物质炭对N2O排放的影响，旨在明确生物质炭对田间N2O排放的持续效应及其作用机理。试验共设置5个处理，分别为CK（不施氮肥和生物质炭）、N（施氮肥）、NB0y（氮肥+新鲜生物质炭）、NB2y（氮肥+2年老化生物质炭）和NB5y （氮肥+5年老化生物质炭），动态监测稻麦轮作周期N2O排放，测定水稻和小麦收获后土壤理化性质和氮循环功能基因丰度。结果表明，生物质炭显著降低土壤N2O累积排放量32.4% ~ 54.0%，且表现为NB0y> NB2y> NB5y。与N处理相比，NB0y, NB2y 和NB5y处理显著提高土壤pH值0.6 ~ 1.2个单位、土壤有机碳（SOC）含量21.4 % ~ 58.6%、硝态氮（NO3--N）含量1.7% ~ 31.3%，对土壤pH改善能力随着生物质炭老化而下降。生物质炭处理显著提高nosZ基因丰度54.9% ~ 249.4%，土壤 (nirS+nirK)/nosZ比值随着生物质炭老化而增加。相关性分析表明，土壤N2O累积排放量与pH值呈显著负相关，与NO3--N含量和amoA-AOB（氨氧化细菌）丰度呈显著正相关。因此，新鲜和田间不同时间老化生物质炭均能显著改善土壤理化特性，降低土壤 N2O排放且新鲜生物质炭的作用效果优于老化生物质炭。土壤NO3--N 含量及(nirS+nirK)/nosZ比值的增加，是导致老化生物质炭减排N2O能力降低的主要原因。
[Objectives] Biochar is an important soil amendment material, as it plays an increasingly prominent role in carbon sequestration and greenhouse gases mitigations, especially in nitrous oxide (N2O) mitigation. To investigate the effects and the mechanisms of the biochar aging process on soil N2O emissions under a rice-wheat rotation system, an in situ field experiment was conducted. [Methods] Five treatments were established as follows: CK (without urea and biochar), N (urea), NB0y (urea with fresh biochar), NB2y (urea with 2-year aged biochar) and NB5y (urea with 5-year aged biochar). Soil N2O emission dynamics were monitored during rice and wheat annual rotation. Also, soil physicochemical characteristics and the abundance of relevant microbial functional genes during the N2O production process were determined after rice and wheat harvest. [Results] Biochar treatment significantly reduced the cumulative N2O emissions by 32.4% - 54.0%, with the reduction capacity following NB0y> NB2y> NB5y. Compared with the N treatment, NB0y, NB2y and NB5ytreatment significantly increased soil pH by 0.6 -1.2 units, soil NO3--N content by 1.7% - 31.3%, and soil organic carbon (SOC) content by 21.4% - 58.6%. Nevertheless, the ability of biochar to improve soil pH was decreased with aging. Also, NB0y, NB2y and NB5ytreatments significantly increased the abundance of nosZ gene by 54.9% -249.4%, and the soil (nirS+nirK)/nosZ ratio increased with the biochar age. Meanwhile, the cumulative N2O emissions showed a significant negative correlation with soil pH, and a positive correlation with NO3--N content and amoA-AOB gene abundance. [Conclusions] In summary, both fresh and aged biochar can significantly improve soil physical and chemical properties and decrease soil N2O emissions, but the effect of fresh biochar was better than that of aged biochar. The mitigation capacity of aged biochar decreased mainly due to the increase of soil NO3--N content and (nirS+nirK)/nosZ ratio.
ZHU Shuangge, ZHANG Qianqian, XU Xintong, BI Ruiyu, SONG Yanfeng, XIONG Zhengqin. Mechanisms of Diminishing Capacity for Mitigating Nitrous Oxide Emissions by Field-aged Biochar in the Rice-wheat Rotation Ecosystem[J]. Acta Pedologica Sinica, DOI:10.11766/trxb202108250452,[In Press]