Infiltration Characteristics Of Verticle Tube Sub-irrigation

Vertical tube sub-irrigation is a new type of water-saving irrigation technology, the resulting underground drip irrigation with water saving, energy saving, small investment,irrigation uniformity, no-blocking, and the advantages of long service life. Indoor test, the method of combining the theoretical and calculation analysis had been used to carry out the vertical tube sub-irrigation infiltration characteristics of experimental research. Basically has the following conclusion:(1) The effect of pressure head on cumulative infiltration and infiltration rate was largest and then gradually became weak with the time going. The cumulative infiltration in sandy loam was higher than that in the silt loam under the same pressure head and vertical tube diameter;the cumulative infiltration increased with increasing verrtical tube diameter under the pressure head of 2 m, but its change decreased with the increase of vertical tube diameter; the stable infiltration rate was 0.53-1.25 L/h when the pressure head was 0.5-3.0 m and the vertical tube diameter was 4-16 mm.(2) In the influencing factors of infiltration, the effect of pressure head on cumulative infiltration was the largest among all the factors and was the major factor, and followed by vertical tube diameter, soil bulk density and initial soil moisture content.(3) The result of muddy water infiltration experiment pointed out that: the effect of vertical tube diameter on cumulative infiltration was the largest among all the factors and was the major factor, and followed by soil bulk density, emitter buried depth, sand content and initial soil moisture content, however, the effect of pressure head on cumulative infiltration was smaller than the others.(4) Vertical tube sub-irrigation wetting body elliptic globular, vertical direction and horizontal direction migration distance of wetting peak as the infiltration time gradually increased gradually, but after the infiltration time increases to a certain time point, increased migration distance of wetting peak amplitude decreases. Horizontal migration distance between vertical wet moist peak migration distance between positive migration distance and negative migration distance.(5 ) The empirical equation was established between cumulative infiltration and influence factors, and the analysis result indicating that the established model was good at cumulative infiltration estimation under irrigation system with vertical tube emitter. The infiltration rate had a positive correlation with pressure head and vertical tube diameter, however, had a negative correlation with initial moisture content and soil bulk density. As well as, the empirical equation of muddy water was established between cumulative infiltration and influence factors, and the analysis result indicating that the established model was good at cumulative infiltration estimation under irrigation system with vertical tube emitter. The infiltration rate had a positive correlation with pressure head and vertical tube diameter, however, had a negative correlation with initial moisture content, soil bulk density, emitter buried depth and soil clay index. The sensitivity index of vertical tube diameter increases with the increase of vertical tube diameter showed that the consequence of vertical tube diameter was larger on infiltration rate with the diameter increase. And also, the calculation model of the displacement of wet peak is constructed, and the results show that the prediction results are better, which can reflect the relationship between the wet distance and the factors.