Study On Soil Water Transport Characteristuc Under Dynamic Pressure Drip Irrigation

The proposed method of dynamic hydraulic drip irrigation system provides a new way to solve the problem of emitter congestion.Compared with the constant pressure drip irrigation,the flow rate of the emitter showed a periodic change under the condition of dynamic drip irrigation,and the soil water migration characteristics changed..At present,there are few studies on soil water movement characteristics and influencing factors under dynamic drip irrigation.The law of soil water movement is the design basis of the whole dynamic hydraulic drip irrigation system.Therefore,it is necessary to study the characteristics of soil water migration under dynamic hydraulic drip irrigation,determine its influencing factors and relevant laws,and provide the theoretical basis for the rational design of dynamic drip irrigation system and the effective management of crop water.This paper uses the method of indoor experiment and numerical simulation to analyze the change process of soil moisture and soil water content under dynamic water pressure(trigonometric function)drip irrigation.The effects of dynamic pressure fluctuation parameters(basic water pressure,amplitude and period)on soil water migration were analyzed,and the soil infiltration characteristics under dynamic hydraulic drip irrigation were studied.The conclusions are as follows:(1)Under the condition of dynamic water pressure and constant pressure drip irrigation,the soil wetting body shape showed an approximate ellipsoid at the end of irrigation.In the early stages of irrigation,the horizontal distance of the wet distance is greater than the vertical direction of the wet distance,wet body shape similar to the larger flatness of the 1/4 ellipsoid.(2)In the initial infiltration of the same basic water pressure,under the dynamic water pressure and constant pressure drip irrigation conditions,the horizontal direction has shown a strong infiltration capacity,in the same time the horizontal wet distance is much larger than the vertical wet distance,With the infiltration time,the wet ratio decreased,the horizontal and vertical wetting rate decreased slowly.Under the same hydraulic pressure,the soil moisture has stronger vertical infiltration capacity under the dynamic water pressure drip irrigation condition,while the soil water content under the constant pressure drip irrigation has stronger horizontal infiltration capacity.The migration distance and velocity of the wet front with time in horizontal and vertical directions can be fitted with a power function,which has a good correlation,and the correlation coefficient R ^ 2 is above 0.9.(3)the distance from the drip drip point under different treatments is closer to the moisture content and the stable time is different.When the base pressure is equal to the same time to achieve a stable time,the performance of the trigonometric function waveform pressure to achieve stability.The monitoring point of water content changes are basically the same,quickly increased to stabilize to saturation.When the basic pressure is the same,the moisture content of the trigonometric function under the pressure of the monitoring point before the saturation is not reached is greater than the constant pressure condition.(4)Under the condition of dynamic water pressure and constant pressure drip irrigation,the distribution of water content contours is basically the same.However,the same basic pressure under different pressure mode,the water content contours are different in shape,the trigonometric function of the waveform pressure to the lower part of the drop,more steep,and constant pressure contour is more gentle.Trigonometric function Wave pressure under the direction of the drip to maintain a large amount of water,with strong water retention capacity,water use rate is high,there is no deep leakage.(5)By comparing the measured values of soil water under different experimental factors with the simulated results and the results of the final soil moisture profile,the simulated infiltration effect is basically consistent with the measured,Under the conditions of soil infiltration moisture distribution law,can be more realistic reflection of the triangular function of the wave pressure under the conditions of soil moisture migration law for the dynamic pressure drip irrigation system and the rational design of different infiltration parameters under the conditions of soil water body is the most distributed distribution Maybe.(6)In the initial stage of infiltration,increasing the base pressure can make the infiltration distance in the horizontal direction show a significant increase trend,but not obvious in the vertical direction;increase the amplitude of the vertical direction of the infiltration,The distribution of water in the whole moist body can be changed,and the distribution of moisture in the whole moist body can be changed,and the distribution of the wetting circle can be changed.The direction of the infiltration.With the pressure cycle continues to increase,wet body saturation area is also increasing,so that the wet body to the bottom of the drop.