Effect of initial water content on vertical line-source infiltration characteristics of soil

For solving the problem presented in the application of infiltration irrigation system in deep rooted plants, a vertical infiltration irrigation device was proposed. Experiments about vertical line-source infiltration characteristics of sand loess and lou soil with different initial soil water contents were carried out in laboratory with this device. The results showed that the three-dimensional infiltration processes for the two soils could be described well by revised Philip infiltration equation. For a given time, there was a negatively quadratic function relationship between accumulative infiltration and initial water content for sand loess and lou soil. The maximum horizontal distance, vertical distance, and horizontal-vertical ratio of the two soils had quadratic parabola relations with initial water content. Comparison of the two soils indicated that the accumulative infiltration of sand loess with more sand particles was greater than that of lou soil under lower initial water content. With the increasing of initial water content, reduction speed of the accumulative infiltration of sand loess was faster than that of lou soil. The critical initial water content of lou soil with more clay particles was higher than that of sand loess, but its infiltration range was lower than that of sand loess. The results could provide some guidelines for vertical line-source irrigation technology in different soils.