水氮耦合协调设施土壤供氮的效应及机理

The research of the soil nitrogen supplying characteristics of water-nitrogen coupling in greenhouse vegetable production has a great significance for increasing irrigation and nitrogen fertilizer use efficiency, developing the reasonable water-nitrogen management and preventing and controlling soil degradation. The project intends to base on the water and nitrogen coupling experiment in greenhouse,and detailedly measures dynamic changes of the soil organic nitrogen mineralization process, various forms and components in situ field after the application of 15N labeled urea by using 15N isotope tracing technique.The significant contribution to soil nitrogen supply potential was explored and the nitrogen supplying mechanism of the greenhouse soil was revealed around the change of the component of soil organic nitrogen and the number of soil mineralizable nitrogen in the condition of water and nitrogen coupling, and by analyzing the quantity and characteristics of soil organic nitrogen mineralization (including mineralization into inorganic nitrogen, SON), soil organic nitrogen components,soil biological (soil microbial biomass nitrogen) and abiotic immobilization nitrogen (fixed ammonium content), and by analyzing the relationship between the components of soil organic nitrogen, nitrogen immobilization and mineralization of organic nitrogen, the relationship between soil available nitrogen, organic nitrogen components, nitrogen immobilization and vegetables nitrogen absorption.The research results could provide scientific basis for clarifying the soil nitrogen supply characteristics and mechanism and theoretical basis for water-nitrogen coupling theory of greenhouse vegetable.

设施土壤供氮特征的研究对于提高水氮利用效率，合理的水肥管理及解决土壤质量退化问题意义重大。本项目拟以设施水氮耦合田间试验为基础，利用15N同位素示踪技术，通过田间原位试验，详细测定15N标记的尿素施用后设施土壤有机氮矿化，氮素的各个形态和组分、15N丰度的动态变化。通过分析土壤有机氮矿化数量（包括矿化成的无机氮、可溶性有机氮）、特征以及土壤有机氮组分和土壤氮素的生物（微生物量氮）和非生物固持（固定态铵含量）数量，围绕土壤有机氮组分及可矿化氮数量的变化，通过分析土壤有机氮组分、氮固持与有机氮矿化之间的关系，土壤有效氮、有机氮组分、氮固持与蔬菜吸氮量之间的关系，探明水氮耦合下有机氮及土壤可矿化氮对土壤供氮潜力的贡献，揭示水氮耦合协调设施土壤的供氮机理。该项研究结果为明确设施蔬菜供氮特征和机理提供科学依据，为设施蔬菜水氮耦合理论提供理论基础。

项目组在设施水氮耦合试验的基础上，研究了水氮耦合对设施土壤供氮能力（氮供应特性）和潜力（有机氮组分及比例）的影响、对设施土壤氮素固持（生物和非生物固持氮）及吸收利用（设施盆栽油菜和番茄）的影响，初步探讨了水氮耦合对设施土壤供氮机理。主要研究成果如下：. 1. 明确设施土壤的矿质氮和可溶性有机氮在番茄生长期的重要作用，可溶性有机氮占可溶性总氮的比例较高，其平均达50%以上，是设施土壤可溶性氮素的主要形态。水氮单一及交互效应均对最大累积净矿化氮量、表层土壤矿质氮有显著影响。随生育期延续，灌水及施肥均显著影响表层土壤矿质氮含量，高灌水下限下过量氮肥的施用会降低净矿化氮量。. 2. 明确水氮耦合设施土壤有机氮组分在酸解氮和非酸解氮中分配比例差异明显。设施土壤酸解氮各组分含量及占全氮分配比例的大小顺序为氨基酸氮/氨态氮>未知氮>氨基糖氮，酸解铵态氮和氨基酸氮是设施土壤中最主要的有机氮形态，与土壤矿质氮，三者是设施土壤供氮潜力的表征。. 3. 明确水氮耦合对设施土壤生长期固持氮组成的影响较小，固持氮以非生物固持为主，占固持氮总量的79.85-86.60%。灌水下限影响非生物固持氮数量，而氮肥用量对生物固持氮、非生物固持氮的比例达到5%显著影响。. 4. 明确水氮耦合对盆栽油菜、设施番茄吸氮量及不同生育期氮素吸收来源及比例有显著的影响，不同生育期油菜和番茄吸收的氮素70%以上来自土壤，吸收的肥料氮90%分布在叶片，而80%集中在番茄果实，15N示踪技术明确了肥料的当季和二季的吸收率、残留率和损失率，确定了油菜、番茄利用率最大，损失率最小的水氮组合。. 5. 初步明确水氮耦合对设施土壤供氮效应，土壤固持氮与可溶性氮呈显著正相关；微生物量氮与土壤酸解氨基酸态氮关系呈负相关，与酸解氨基糖态氮和铵态氮呈正相关。土壤全氮、有机碳和硝态氮是影响土壤供氮潜力的最显著因素。. 本研究成果为明确设施土壤水氮供氮潜力、特征及机理提供了科学的依据，为设施蔬菜合理的水氮管理提供了重要的理论支撑。