Simulation Experiment On Infiltration Characteristics Under Subsurface Irrigation With Microporous Ceramic Emitter

The subsuface irrigation with microporous ceramic is an energy-saving and environment-friendly irrigation in which the microporous ceramic emitters are placed at a depth in the ground and the irrigation water is slowly transported to the soil in the root zone of the crop under low working pressure.In this study,the non-pressure irrigation of microporous ceramic emitters was carried out indoors to simulate the field experiment,and investigate how the initial soil moisture content,depth and evaporation affect the infiltration characteristics of microporous ceramics,respectively,so as to determine the structural design and field application parameters of the emitter.The main conclusions are as follows:(1)The wet front migration distance increases with the increase of soil initial water content,and the relationship between wet front migration distance and infiltration time is a power function;the soil moisture content around the emitter increases rapidly with the infiltration time,and finally stabilizes.The lower the initial soil moisture content,the higher the soil moisture content reaches the stable value and the shorter the time;the cumulative infiltration becomes smaller as the initial soil moisture content increases.The relationship between cumulative infiltration and time is analyzed,and the cumulative infiltration prediction model of underground microporous ceramic irrigation under different initial water content conditions is constructed with good precision.(2)The flow rate of the emitter under different buried depths gradually decreases with the increase of infiltration time,and finally approaches 0;the initial flow rate gradually increases with the increase of the buried depth,the reason is that the soil matrix suction area above the emitter is different in size.For example: the initial flow rates of 5,10,20,and 30 cm are 0.66,1.01,1.22,and 1.32 L/h,respectively.It can be seen that the soil matrix suction area that affects the initial flow rate is a sphere with a maximum radius of 20 cm centered on the emitter.The variation law of the horizontal migration distance and the infiltration time of the wet front is similar under different burial depths.The horizontal migration distance and the vertical migration distance all have a power function relationship with the infiltration time.The average water content in the wetted body gradually increases with time,and finally tends to be stable,and the greater the buried depth of the emitter,the higher the average moisture content in the wetted body.The relationship between cumulative infiltration and time is in accordance with the Kostiakov infiltration model.Based on this,a semi-empirical infiltration model of cumulative infiltration,depth and infiltration time is constructed.(3)For the buried depths of 5 and 10 cm,the emitter flow and soil evaporation intensity increase with the increase of atmospheric evaporation force;when the buried depth increases to 20 and 30 cm,the flow rate and soil evaporation intensity change little with the increase of atmospheric evaporation force,and the two curves that change with time basically coincide.It is further verified that the soil matrix suction region affecting the outflow of the emitter is a sphere with a maximum radius of 20 cm centered on the emitter.In the field application,if the depth of the microporous ceramic emitter is set at 20 cm or more,the soil evaporation intensity can be reduced,and the ineffective water loss caused by field evaporation can be avoided,thereby improving the irrigation water utilization rate.