沟灌施肥对土壤硝态氮运移的影响及其技术参数优化研究

Furrow irrigation fertigation is the application of fertilizers with furrow irrigation water. It has great potential for application in irrigated farmland. Furrow irrigation fertigation parameters such as furrow inflow rate, concentration of nitrogen application, the duration of the fertigation and the size of furrows, have an influence on the efficiency and uniformity of nitrogen application. An improper furrow irrigation fertigation could easily lead to uneven distribution of nitrogen in the soil profile and deep percolation of nitrate. Therefore, to improve the uniformity of nitrogen application and to reduce the nitrate leaching, the optimization of furrow irrigation fertigation parameters is very important. This project seeks to develop proper design and management approaches and guidelines, for N-fertigation operations in furrows, through experimental and modelling studies. The selected sandy loam soil in this study is widely distrbuted in the Jianghan Plain. Simulation experiments will be conducted with the nitrate and bromide tracers. This study focus on the vertical and lateral transport of nitrate under furrow irrigation fertigation, and the effects of furrow inflow rates, concentration of nitrogen application, the duration of the fertigation and the furrow size on the transport of nitrate at the scale of cross-section. The HYDRUS-2D model will be applied to simulate the dynamics of nitrate in soil profile under different conditions of fertigation through a cross-sectional furrow. The efficiency and uniformity of nitrogen application would be calculated compared between different scenarios, and then determine the relationships between efficiency and uniformity of nitrogen appllication and furrow irrigation fertigation parameters, including furrow inflow rates, concentration of nitrogen application, the duration of the fertigation and the size of furrow. The optimum combined mode of furrow irrigation fertigation parameters will be proposed. The results of this study will provide design guidelines and management strategies for furrow irrigation fertigation systems.

沟灌施肥技术在灌溉农田中具有极大应用潜力，然而沟灌施肥技术参数设计不当，易造成土壤剖面氮肥分布不均、深层渗漏等问题。因此，优化沟灌施肥技术参数提高施氮均匀度和施氮效率，成为关注热点。本项目针对沟灌施肥条件下垄沟断面硝态氮二维（垂向和横向）迁移问题，选取江汉平原农业区分布最广的砂壤土，利用沟灌模拟装置，采用硝态氮和溴化物两种示踪剂，研究沟灌施肥条件下垄沟断面硝态氮垂向和横向迁移特性，弄清入沟流量、施氮量、灌水/施肥历时、垄沟规格等技术参数对硝态氮垂向和横向迁移的影响规律。应用HYDRUS-2D模型模拟不同沟灌施肥条件下硝态氮垂向和横向迁移动态，计算对比不同情景下施氮效率和施氮均匀度，确定施氮效率和施氮均匀度与入沟流量、施氮量、灌水/施肥历时和垄沟规格的定量关系。从保证最佳施氮效率和施氮均匀度角度，提出沟灌施肥技术参数优化组合模式。研究成果可为沟灌施肥技术设计和优化管理提供科学依据。

沟灌施肥技术在灌溉农田中具有极大应用潜力，然而沟灌施肥技术参数设计不当，易造成土壤剖面氮肥分布不均、深层渗漏等问题。.本项目针对沟灌施肥条件下垄沟断面硝态氮二维（垂向和横向）迁移问题，选取江汉平原农业区分布广泛的灰潮土为研究对象，利用沟灌土槽装置和模型模拟，研究沟灌施肥下垄沟断面硝态氮垂向和横向迁移特征，探讨土壤质地、肥液深度、沟底覆膜、初始含水量、施氮量等技术参数对硝态氮迁移分布的影响规律。.研究结果表明：（1）质地对土壤硝态氮分布影响显著。相对与粘壤和粉壤，砂壤深层硝态氮所占比例最大。（2）高施氮量条件下土壤湿润锋附近的硝态氮含量较高，造成深层渗漏风险较大。（3）灌施肥液深度对垄沟断面土壤硝态氮迁移分布影响明显。相同灌施量条件下，灌施肥液深度增加，可减少深层土壤中硝态氮占总土层的质量百分比。（4）随着土壤初始含水量增加，垄沟断面土壤硝态氮横向和垂向运移距离明显增大，土壤深层硝态氮所占比例显著增加。（5）沟底覆膜处理可促进土壤硝态氮在垄沟断面横向入渗，使硝态氮在垄沟间分布更加均匀，提高施氮均匀度，有利于减少沟底土壤硝态氮淋失。.项目研究成果可为沟灌施肥技术设计和优化管理提供理论依据，具有重要的科学价值和现实意义。.