秸秆对我国北方设施菜地土壤硝态氮固持转化的作用机制

The greenhouse vegetable developed rapidly in north China, but the nitrate-N accumulation caused by high fertilization has become an important obstacle for its healthy development. It is reported that straw possesses the ability to improve the immobilization and transformation of nitrate-N in greenhouse soil, but very little work has focused on the variety of characteristics and mechanisms through which straw may directly or indirectly influence the immobilization and transformation of nitrate-N under different age greenhouse soil. Carbon nitrogen ratio (C:N ratio) stoichiometric characteristics and soil microbial characteristics are the basic basis to study the biogeochemical cycle of ecological, and play the key role in soil nutrient cycle. Aiming at the different age greenhouse vegetable soil, the project, combining ecological stoichiometry theory and microbial ecology theory, will use the laboratory simulation experiments and the field test to investigate the following major research contents: the influence characteristics of straw on the nitrate-N immobilization and transformation in greenhouse soil; the effect of straw on the C:N ratio stoichiometric characteristics in greenhouse soil; the effect of straw on the microbial action in greenhouse soil. The 15N isotope labeling method and various microbial ecological analysis techniques (such as CLPP, TGGE, ect.) will be used in this study. The results of this research will clarify the interactions among the C:N ratio stoichiometry characteristic and soil microorganism, reveal the influence mechanism of straw on the nitrate-N transformation in greenhouse soil, and provide reliable scientific guidance for the control technology of soil nitrate-N accumulation and the rational utilization of straw.

我国北方设施菜地发展迅猛，而由高施肥导致的硝态氮累积却成为设施菜地健康发展的重要阻碍。秸秆具有促进土壤硝态氮固持转化的作用，但其在不同棚龄设施菜地土壤中对硝态氮的固持转化作用特征和作用机制还缺乏深入系统的研究。碳氮比化学计量特征和土壤微生物特征是研究生态系统中生物地球化学循环的基本依据，在决定土壤养分循环方面起关键作用。本项目以不同棚龄设施菜地土壤为研究对象，将生态化学计量学理论与微生物生态学理论相结合，采用室内模拟和田间试验，利用同位素标记(15N)及多种微生物生态学技术（CLPP、TGGE等），重点研究:秸秆对土壤硝态氮固持转化的影响特征；秸秆对土壤碳氮比化学计量特征的影响；秸秆对土壤生物行为的影响。研究结果将阐明土壤碳氮比化学计量特征与土壤微生物之间的互作关系，揭示秸秆对设施菜地土壤硝态氮固持转化的作用机制，为研发设施菜地土壤硝态氮控制技术和合理利用秸秆提供可靠的科学依据。

本项目围绕秸秆、生物炭、有机肥等外源碳材料对土壤硝态氮固持转化作用机制开展了一系列研究：（1）系统研究了稻油轮作模式下秸秆还田对土壤硝态氮固持转化的影响作用，发现秸秆还田能够提高作物产量和含氮量，增加土壤碳库储量，增强土壤微生物的氮素固持能力，有效降低土壤氮素流失风险；（2）开展了玉米秸秆生物炭、稻壳生物炭、棉籽壳生物炭等对土壤氮素迁移转化规律、土壤生物行为特征及微生物群落结构的影响研究，结果表明，生物炭能够有效改善土壤的理化性质，增加土壤SOC含量，增强土壤的持水能力，提高微生物量含量，改变土壤的微生物群落结构，促进土壤氮固持能力，提高作物产量。（3）系统研究了有机肥、化肥等不同施肥方式对菜地土壤氮素径流损失以及土壤理化性质和微生物量的影响，揭示了施用有机肥可降低Nmin/TN比，降低氮素径流损失，表明有机肥替代技术可降低土壤氮淋失风险。本项目研究表明，秸秆还田、施用生物炭、有机肥替代等技术都对土壤硝态氮固持具有积极作用，并与土壤SOC、土壤水分固持能力、微生物量等具有正相关关系；意味着外源碳的添加能够有效增强土壤对硝态氮的固持能力，降低土壤氮素流失风险。