基于保护性耕作长期试验的潮土团聚体形成与有机碳累积机制研究

Maintenance of sustainable farmland productivity in the intensive agriculture is an important task in our country. Conservation tillage is a developing approach to achieve intensive agriculture and improvement of soil productivity simultaneously. The long-term effect of conservation tillage on the cultivation of soil productivity is an advanced topic in the current research area of soil science and agronomy. The project prepares to use a long-term fixed trial of conservation tillage in Fengqiu agro-ecological experimental station, Chinese Academy of Sciences as platform, to study the carbon sequestration mechanism in soil aggregate, degradation process of different straw and its contribution to soil aggregate formation and organic carbon accumulation, action mechanism of microorganism on soil aggregate formation and organic carbon accumulation under the conservation tillage and winter-wheat and summer-maize rotation on a fluvo-aquic soil in the Huang-Huai-Hai Plain. The investigation will be achieved by plot experiment and indoor control culture, combined with stable carbon isotope, nuclear magnetic resonance and molecular biology technique. The objectives of this research are to unravel the mechanism of different tillage and straw management on soil aggregate formation and organic carbon accumulation, to clarify the long-term effect of conservation tillage on the cultivation of soil productivity, to provide theoretical support for sustainable farmland productivity under intensive agriculture in fluvo-aquic soil region.

高强度种植条件下如何维持农田生产力的可持续是我国当前面临的重要课题，保护性耕作是正在发展中的实现农田高强度种植与地力提升共济的新途径，其对农田地力培育的长期效应研究是当前土壤学和农学研究的前沿内容。本项目拟以中国科学院封丘农业生态试验站保护性耕作长期定位试验为平台，以黄淮海平原潮土为研究对象，通过田间小区试验和室内控制培养实验相结合，借助稳定性碳同位素、核磁共振、分子生物学等相关分析技术，针对冬小麦/夏玉米一年两熟保护性耕作制度下土壤团聚体的固碳机制、不同类型秸秆降解过程及其对土壤团聚体形成和有机碳累积的贡献、微生物对土壤团聚体形成和有机碳累积的作用机制等展开研究。阐明不同耕作和秸秆管理措施对团聚体形成和有机碳累积的作用机制，明确保护性耕作对土壤地力培育的长期效应。为潮土高强度种植下的生产力可持续发展提供理论支撑。

保护性耕作是正在发展中的实现农田高强度种植与地力提升共济的新途径，其对农田地力培育的长期效应研究是当前土壤学和农学研究的前沿内容。本项目依托中国科学院封丘农业生态实验站内保护性耕作长期定位试验，利用团聚体分级、有机碳分组、核磁共振和分子生物学等相关分析技术，针对冬小麦/夏玉米一年两熟保护性耕作制度下潮土团聚体形成和有机碳累积的作用机制展开研究；同时，借助野外盆栽试验和原位培养试验，利用13C同位素示踪和稳定同位素探针技术，探究作物秸秆降解过程及其对土壤团聚体形成和有机碳累积的贡献。研究结果表明：以少免耕和秸秆还田为主的保护性耕作措施主要促进了0–10 cm土层潮土水稳性大团聚体形成和有机碳积累，并且大团聚化进程与活性有机碳的累积密切相关。通过核磁共振将土壤有机碳划分为8种不同的官能团分子结构，结果发现methoxyl/N-alkyl C和O-alkyl C是保护性耕作下驱动潮土水稳性大团聚体形成最重要的活性有机碳组分；通过回馈机制，保护性耕作又能通过提高粗大和细大团聚体中优势碳官能团组分的累积效率，实现全土有机碳的累积，而各碳官能团组分的含量与颗粒有机碳的分布密切相关。免耕和秸秆还田能有效提高土壤纤维素降解细菌的数量及多样性，同时改变其群落结构组成。大团聚体形成通过改变土壤水气微环境，进而制约微生物丰度和群落结构；保护性耕作条件下土壤微生物群落向真菌和厌氧微生物转变，同时联合大团聚化进程，共同促进了表层土壤有机碳的累积。秸秆还田通过加快潮土大团聚化进程和改变微生物群落结构及其代谢活性，能有效促进作物秸秆碳在土壤中的累积；同时土壤微生物对秸秆碳的代谢特征又受到土壤地力水平的显著影响。耕作模式对小麦和玉米产量的影响不受秸秆还田而显著改变；但基于秸秆还田对土壤地力和作物产量的提升效应以及二者对土壤长期免耕后间歇性翻耕的正响应，综合考虑生产成本与农田生产力可持续性，少耕耦合秸秆还田可以作为维持黄淮海平原农业可持续性发展的最佳策略之一。