关键词: 壤砂土, 垂直入渗, 入渗水头, 湿润锋, 累积入渗量

Abstract: Infiltration is the movement of water into the soil profile，which has an important role in field water cycle. The influence of different infiltration head on characteristics of one-dimensional vertical infiltration characteristics of loamy sand has been studied based on vertical infiltration experiments in laboratory. The results showed that the relationship between cumulative infiltration（I）and infiltration time（t）is consistent with Kostiakov-Lewis model[I（t）=At^α+Bt]and Philip model[I（t）=St^0.5+B′t]；The parameter A value increases with the increase of infiltration head （h）；There existed fairly good linearity between the parameter A value，soil water sorptivity S and infiltration head（h），the slope of them are equal to 0.007 4 and 0.006 6，respectively；the parameter α value ranged from 0.462 2 to 0.538 9，and its mean value is equal to 0.492 6；the parameter B varied between and 0.020 0 to 0.020 1，parameter B′ changed from 0.018 7 to 0.021 4. The infiltration coefficient（k）and infiltration index（a）presented the opposite trend with the increase in infiltration heads，which is because of soil water press potential and unsaturated hydraulic conductivity. The relationship between wetting front advancing distance（Z_f）and infiltration time is a power function（Z_f=mtⁿ）. The model parameter m value increases with the increase of infiltration heads and the slope of them is equal to 0.006 4；the parameter [n] value is equal to common logarithm of the ratio of wetting front advancing distance at the end of the tenth unit time to that at the end of the first unit time. The relationship between the cumulative infiltration and wetting front advancing distance is good linear（I=βZ_f），and the slope（β），increases with the increase of infiltration heads，is equal to the difference between mean soil water content（θ_mean）and initial water content（θ_i）in humid region；For any two infiltration heads h₁ and h₂，a relationship was existed about  θ_mean（h₁）-θ_mean（h₂）=β（h₁）-β（h₂）. This research result is of great theoretical value and practical significances to preventing soil erosion，thwarting desertification and protecting ecological environment.

Key words: loamy sand, vertical infiltration, infiltration head, wetting front, cumulative infiltration