长期施肥对洞庭湖区水稻土氮素矿化特征的影响及其机理研究

Soil nitrogen(N) mineralization is the main component of N supply for plant growth, Fertilization actility, especially long-term fertilization mangement can significantly change soil fertility, thus then deeply influenced on the soil N transforamtion and mineralization characteristics. Dongting Lake region is an important agricultural production area with the feature of paddy soils widely distributed and mainly cropped double-rice. In the past, much studies were carried out to study the N process of paddy soils in the area, however, towards the N mineralization chatacteristics, N form transformation and its impact on N mineralization in soil profile under different long-term fertilization practices was rarely reported . In term of that, We take typical paddy soils in Dongting Lake area that are under different long-term fertilization management as study object to carry out the following two studies: Firstly, we study different layer's soil N mineralization characteristics and its response to incubated temperature changes by submerged biological incubation and model simulation methods. Secondly, we analysis the different N forms and soil organic matter's profile distribution characteristics and the relationship between the mineralized N parameters and these different N species, and which is in order to understand the N mineralization mechanism of differences among the different fertilization management modes. This research has a significance in assessing the effect of different long-term fertilization on paddy soil's nitrogen process, strengthening the farmland N management and protecting the regional ecological environment.

土壤供氮是作物吸收氮的主要来源，施肥特别是长期施肥会明显改变土壤肥力状况，进而对土壤氮素形态转化及供氮特性产生深刻影响。洞庭湖区是我国重要的双季稻产区，水稻土是该区主要的土壤类型，剖析该区水稻土氮过程的研究报道较多，而对长期施肥条件下水稻土不同剖面层次氮矿化特征、氮素形态转化及其对矿化作用的影响研究不足。鉴于此，本研究以长期不同施肥措施影响下的洞庭湖区典型水稻土为研究对象，首先通过淹水生物培养实验和模型模拟方法对不同剖面土壤氮矿化特性及其对培养温度变化的响应进行研究；其次通过化学分析实验研究不同形态氮素和有机质剖面分布及与氮矿化特征参数间的关系，探求不同施肥处理间矿化供氮差异机理。该研究对于评价长期不同施肥对水稻土氮过程的影响、加强农田氮素管理和区域生态环境保护有着重要的意义。

土壤氮素矿化是水稻土供氮的重要过程，研究长期施肥影响下水稻土氮素矿化特性及氮素形态转化对于深入认知稻田土壤氮循环对人为措施的响应具有重要意义。本研究基于长期定位试验，研究不同施肥措施对洞庭湖区典型水稻土氮素矿化特性及其温度效应的影响，剖析土壤氮矿化与活性有机碳氮组分、团聚体氮的关系，探析酸解有机氮组分在氮素矿化过程中的行为及对矿化氮的贡献。研究显示，施肥是改善土壤氮素肥力的重要措施，长期不同施肥同步提升土壤氮矿化势和可矿化氮比例，但施肥对土壤氮矿化的提升效应随温度增加而趋于减弱。施肥降低了土壤氮素矿化的温度敏感性，且该效应在表土层较亚表土层表现更为明显。长期施肥提升土壤矿化供氮能力一方面在于明显提升土壤大粒级团聚体(0.5-5 mm)含量及其氮储量及土壤活性有机碳氮比例，另一方面在于显著增加土壤酸解性有机氮特别是酸解氨基酸态氮含量。与化肥施用相比，化肥与有机肥配施更有利于提升土壤矿化供氮能力，且降低氮素矿化的温度敏感性。未来需进一步加强研究施肥条件下土壤氮素转化酶活性的温度敏感性研究及团聚体氮素矿化特性，为深入理解施肥对土壤氮矿化的内在影响机理提供更有价值的依据。