Abstract: N₂O emission and NO^-3-N leaching from cropland are major pathways of reactive N losses in soils, and important sources of global reactive N pollution, resulting in a serious threat to global climate and water environment security. The producing process of cropland reactive N losses is closely related to soil nitrification and denitrification. There exists significant difference regarding to soil nitrification and denitrification under different cultivation systems. Particularly, in our country, long-term and high input of nitrogen fertilization is widespread in continuous cropping farmland of economic crops (e.g., sugarcane), leading to accelerate large-scale soil acidification, and enhance the soil nitrification significantly, which directly affect the change trend and controlling strategy of agriculture-derived reactive N losses. In recent years, as a kind of multi-functional and char-based soil conditioner, biochar has great potential in application for regulating reactive N transformation processes, improving farmland soil, as well as increasing or maintaining crop yield. In this paper, research progress on the status of agricultural soil reactive N losses was reviewed, followed by its main influencing factors and key microbial processes. Furthermore, the potential pathways of biochar amendment to regulate reactive N transformation and nitrogen recycling utilization in cropland were explored, and then the future research direction was also prospected correspondingly, aiming to provide new ideas for the research on the control of reactive N pollution in farmland, efficient utilization of N fertilizers, as well as the development of high-efficiency, green and sustainable agriculture in China

Key words: cropland soil, reactive N losses, N2O emission, NO-3-N leaching, biochar, soil improvement

摘要： 农田N₂O排放与NO^-3-N淋失是土壤活性氮损失的主要途径，是全球活性氮污染的重要来源，对全球气候变化和水质安全构成严重威胁。农田活性氮的产生途径与土壤硝化和反硝化作用密切相关，不同种植体系下土壤硝化和反硝化过程存在很大差异，尤其是我国甘蔗等经济作物连作农田长期大量施肥导致大面积土壤加速酸化、土壤硝化程度不断加强，直接影响到农业源活性氮库的变化趋势和控制策略。近年来，生物炭作为一种被广泛关注的多功能化炭基土壤调理剂，在农田活性氮转化调控、土壤改良、农作物稳产增产中具有重要的应用潜力。综述了农田活性氮的损失现状、主要影响因素及其关键微生物过程，指出了生物炭在农田活性氮转化和氮素循环利用中的潜在调控途径，并展望其未来研究发展方向，为我国农田活性氮污染控制、氮肥高效利用以及农业高效绿色与可持续发展研究提供新思路。

关键词: 农田土壤, 活性氮损失, N₂O排放, NO^-3-N淋失, 生物炭, 土壤改良