Research On Soil Water Movement Characteristic Under Microporous Ceramic Emitter Irrigation

Microporous ceramic emitter irrigation is a new irrigation technique with higher water-saving` efficiency. Microporous ceramic emitters is the main component and water potential difference of emitter is the driving force. Adjusting water flow rate based on soil water moisture, this irrigation technique can wet the soil near the roots of plants precisely and slowly. As a new irrigation technique, it should be tested to make its parameters clearly before its large-scale application. However, operating parameters are closely related to soil moisture movement. Therefore, it is necessary to do some research on the soil moisture movement of porous ceramic emitters irrigation. In order to obtain some reliable operating parameters and provide references for its large scale applications, we carried out soil box indoor experiment and hydrus-3d simulation to figure out the soil moisture movement of microporous ceramic emitter irrigation. The main research conclusions were as follows:( 1) It showed a certain regularity coupling both for infiltration rate and for water potential inside and outside the emitter, when the water pressure was 0 m for irrigation in the clay loam soil. The emitter could irrigate continuously the steady flow rate of emitter as small as 0.1l/h. Compared with ordinary subsurface drip irrigation, there wasn’t "redistribution" phenomenon of infiltration. It could supply water for roots of plants slowly and obtain moisture content above 40% in a small area next to the emitter, didn’t reach the saturated moisture yet. There was ponding around emitter. It did not cause deep percolation, could meet the requirement of long-term water uptake for plant slowly.(2)Water pressure and soil texture had a significant impact on the process of infiltration under ceramic emitters irrigation. Water pressure was the key factor to determine the initial soil moisture infiltration rate and cumulative infiltration.Water pressure also effected the time needed to reach stable infiltration and had slight influence on the final infiltration rate. Water pressure had great impact on soil moisture distribution. The higher water pressure, the higher water moisture around the emitter and the bigger areas with high moisture content. Soil water cumulative infiltration and infiltration rates in loess soil were much larger than that in clay loam. Wetting front advanced faster and the range of wetting body was relatively larger in loess soil. Wetting body was in different shapes for different soil texture. Wetting body shapebecame pear-shaped. The area with high moisture content was under the position of emitter.Wetting body showed an elliptical shape in clay loam and with the increase of water pressure,the moisture transport became much more quickly in the radial direction and ellipse was more flat.(3)Soil water movement simulated by hydrus-3d was consistent with the results of the indoor experiment. Hydrus software can be used to predict infiltration of micoporous ceramic emitters.The simulation results showed that the flow of ceramic emitter could effect the sizes of wetting body when the amount of irrigated water was same. However, the greater the flow,the greater the range of the high moisture surrounding emitter. Installation depth had little effect both on wetting body size and shape, but had strong influence on soil moisture at the same position. The flow of the ceramic emitter could be changed by changing the inner or outer diameter(wall thickness) and the length in structural dimensions.(4)It showed that irrigation amount was between 10L/d ~ 15L/d Ceramic emitter in loess soi. So the ceramic emitter could be applied to loess soil(north of Shaanxi, etc.) for fruit trees and other forest irrigation. Suitable installation depth was 30cm; Irrigation amount was between 2 /d~5L/d in clay loam. Soil moisture reached to 21.6% when the wetting front radius was between 10 and 15 cm, which arriving 90% of Field water capacity and can meet growth needs of dwarf plants. If the ceramic emitter was applied to crops, it would be suitable for vegetables with smaller amount and suitable depth was 20 cm.