中文摘要：

土壤在干燥脱水的过程中易收缩产生裂隙。裂隙的产生是土壤性质与外界条件等多种因素综合作用的结果，其形态结构也非常复杂，难以准确描述。裂隙能够作为优先流的路径，增加农田水分和养分的流失以及地下水污染的风险。本文总结和归纳了裂隙产生的影响因素、裂隙的表征指标与测定方法、裂隙导致的优先流的研究方法、裂隙对优先流的影响和模拟等方面的研究进展。今后应进一步加强裂隙产生机理的全面深入的研究；构建和完善裂隙三维指标体系及其测定方法；推进裂隙导致的优先流的定量化和数学模拟研究；加大田间原位裂隙及其优先流的研究。

英文摘要：

Soil tends to shrink and form cracks when it gets dried up. Soil cracks are formed under the joint effect of a variety of factors, like soil properties and environment conditions, and very complicate and hard to describe precisely in morphological structure. As they may act as pathways for preferential flow, their presence enhances the risks of water and nutrient loss and pollution of groundwater. Soil properties, such as soil clay content, soil mineral composition, soil organic carbon content and bulk density, etc. are the main factors affecting soil cracking, while wetting and drying alternation, tillage and plant growth are its external affecting factors. So far, the characterizing indices and determination methods available for soil cracks focus mainly on their two-dimensional structural features, and little has been reported about characterizing indices and determination methods for three-dimensional structure of cracks. The methods for measuring preferential flow caused by soil cracks include dye tracer, disc permeameter, breakthrough curve, profile soil water potential measurement and so on. Cracks vary in feature with soil water content, so the effect of soil cracks on preferential flow is complicate, and closely related to soil properties, soil water content and depth of the cracks. The dynamic variation of cracks makes it more difficult to simulate preferential flow caused by soil cracks. It is, therefore, suggested that more efforts should be dedicated in future to conducting in- depth complete researches on crack-forming mechanism; establishing three-dimensional index systems and determination methods for soil cracks and improving the systems and methods; promoting researches on quantification and mathematic simulation of crack-induced preferential flow ; and enhancing in situ field study of cracks and preferential flow.