三峡库区柑桔产业带与三峡水库相毗邻，柑桔园不合理施用氮肥造成氮素淋失，引起人们关切，但国内未见相关深入研究。柑桔园氮素淋失不仅涉及区域水环境保护，氮素淋失涉及的优势流和溶质扩散问题也是当今学术界研究的热点。本项研究采用小区试验、室内模拟实验和野外实地观测相结合的方法，利用优势流图像分析技术和15N同位素标记手段，深入研究柑桔园不同氮素用量梯度、不同水肥管理措施对氮素淋失的影响规律；分析自然土壤结构与孔隙条件与优势流的形成，柑桔园自然土壤大孔隙的分布与产生规律；探讨不同肥料氮素残留梯度与自然土壤大孔隙存在对氮素淋失过程的交互作用动力机制，从而揭示水肥管理与自然土壤大孔隙对柑桔园氮素淋失影响机理。该项工作对于优化柑桔园水氮调控，改进土壤管理，保护区域水环境具有重要的现实意义；有关柑桔园优势流与氮素梯度对于氮素淋失作用动力机制和柑桔园孔隙分布与优势流特征的研究，是拟对相关领域的深入探索。

Citus is the major crops adjacent the flunctuation belt of the great artificial reservoir in the Three Gorges Area.The irrational chemical fertilizer application for citrus agriculture is leading to the increase of nitrogen diffusion through leachate from citrus sloping land.However,there is rarely research concerning the management of water and nitrogen in citrus garden in China.In this research,plots experiment and soil collum simulation and the structure of soil pore investigation will be carried out, soil prefrential flow imaging technology and 15N isotope labeling will be used.The mechanism of the key factors which influencing the transference of water and nitrogen in citrus sloping land, and the intergration of both on nitrogen loss by leachate will be elucidated.Those factors including the strcture of soil pore, the amounts of the chemical fertilizer applied and the methods for water and nitrogen management.The distribution and the formation of large soil pore in citrus garden will be disclosed also.The influence of factors on nitrogen losses through surface runoff and infiltration will be quantitively assesd.This research will contribute to optimization of the management of water and nitrogen in citrus sloping land for high fruit yield quality,and for the effective reduction of nitrogen loss by infiltration in citrus sloping land, which is especially important in the Three Gorges Area, China.Moreover, this research will also contribute to the understanding of water and nitrogen tranference in citrus sloping land, and is of high academic value.