Study On The Characteristics Of Rainfall Infiltration Under The Condition Of The Different Farmland Underlying Surface Treatment

Due to insufficient rainfall and the shortage of water resources, the semi-arid areas need to make full use of rainwater resources. Drip irrigation under film improves the irrigation water use efficiency in semi-arid area. While reducing irrigation water requirement, the infiltration evaporation interface of farmland water environment was changed by plastic film mulching and ridge and evaporation, infiltration and soil water transport were also affected. Therefore from the view of water cycle in farmland, analysis of the effects on rainfall and infiltration under different farmland underlying surface treatments and revealing the effect of mulching and ridging on rainfall infiltration characteristics in water saving irrigation technology has very important practical significance for high-efficient utilization of precipitation resource and realizing the sustainable utilization of water resources.In this article, the characteristics of rainfall infiltration under the condition of different farmland underlying surface treatments are studied by using the method of artificial rainfall simulation combined with the orthogonal test. The method of orthogonal experiment is used to analyze rainfall infiltration, runoff starting time and changes of moisture content of shallow soil in the course of rainfall. At the same time, the Variation of soil wetting front,vertical soil moisture content and infiltration process of soil after rainfall under the condition of different farmland underlying surface treatment were analyzed. The main research results are as follows:(1) Rainfall intensity is the main factor that influences the infiltration rate and runoff time. The greater the rainfall intensity, the greater the rainfall is, the infiltration quantity also increases and the runoff start time is shorter; Soil infiltration capacity is the most and start time of runoff is the latest under flooding irrigation, furrow irrigation comes second. Soil infiltration capacity is the least and start time of runoff is the earliest under drip irrigation with mulch film. With the increase of soil initial water content, the infiltration rate decreased gradually, and the time of producing runoff begins earlier.(2) The effect of rainfall intensity on the change rate of the shallow soil moisture content was the greatest, followed by initial soil water content and farmland underlying surface. Under the same underlying surface treatment, the greater the rainfall intensity, the greater the change of soil moisture content is. Under the different underlying surface treatment, the infiltration of drip irrigation under mulch film was the fastest. Under the same rainfall intensity, with the increase of initial soil water content, soil infiltration became slow.(3) The wetting front migration is influenced by the rainfall intensity mostly, the greater the rainfall intensity, the faster the migration rate of the wetting front is. In the shallow layer of soil, irrigation migration rate under furrow irrigation is greater than film drip irrigation. Increase as the depth, migration rate under flood irrigation was close to film drip irrigation. In shallow layer of soil, the migration rate on the edge of film drip irrigation film is the fastest, followed by furrows and the center of film. Deep in the soil, migration rate of the furrow is the largest, followed by the edge of film and the center of film.(4) According to the measured data and combining with the analysis, we can say that the greater the rainfall intensity, the greater the spatial variation of soil moisture content is. After a rainfall, the smaller the rainfall intensity, more slowly water content changes; After a long period of rain, it’s conducive to be continuous infiltration of soil water; The water moisture content of shallow soil was uneven, as time goes by, with the passage of time, the degree of uneven decreases gradually.(5) After a rainfall, the soil moisture rate trends of three different positions under furrow irrigation and drip irrigation under film are basically the same, but the furrow of drip irrigation under mulch film changes the fastest, then the side of the film, and finally in the film; after the end of rainfall, the infiltration of soil moisture is influenced by the soil matrix potential and gravity potential.