Study On Water Infiltration Characteristics Of Red Soil Under The Condition Of Bubble Irrigation

Bubble Irrigation is a micro-irrigation technique for fruit trees planting and afforestation which were aimed at the emitter clogging problems in Chinese drip irrigation as well as the low levels of agricultural production and management situation.In recent years,most bubble irrigation mostly researched on orchards test areas planted wide field line crops mainly at arid basin in Shanxi,Hebei,Xinjiang and so on,but for the relatively abundant water resource areas like Jiangxi were few.According to the Bubble Irrigation system designs over the years,the outlet pitches were mainly decided by the growing plants space.In this paper,the soil bulk density,irrigating flow rate and initial soil moisture are considered,after simplified test by orthogonal design software,we studied the infiltration moisture’s migration law in the moist soil under the condition of red soil springs irrigation.Finally,we are forced to the corresponding optimal irrigation coefficient of each study factors by using Orthogonal Design software and SPSS software to analyze three different investigate factors.The specific research results are as follows:(1)The maximum moist radius in horizontal and vertical directions were increasing with the passage of time below the outlet,what’s more,the maximum moist radius moving speed was faster in the initial infiltration than in post-infiltration both in horizontal and vertical directions,and the horizontal wetting front transport distance greater than the vertical wetting front transport distance,but as time goes on,the vertical wetting front infiltration distances were gradually approaching the horizontal wetting front;(2)With the extension of infiltration time,the shape of wetting body changedfrom1/4a lying ellipsoid to 1/4 a whole sphere gradually,and the ellipsoid cross-sectional shape could be showed by a elliptic equation;The infiltration water’s redistribution process focused within 24 h after the end of the irrigation,the migration speed and transport distance of wetting front in the horizontal directions below the outlet are greater than the horizontal direction,and the shape of wetting body is changed from 1/4 full sphere to 1/4vertical ellipsoid;(3)At the end of the irrigation,the moisture in the wetting soil was between 24.72%~34.15%,but reduced to the range of 16.81% ~ 24.04% after the end of the redistribution for 24 h.What’s more,at the same distance from the outlet,the soil water content decreasing with the increased soil depth,and at the same depth behind the soil surface,the soil water content decreasing with increased distance from the outlet,but the decreasing rate of was smaller;(4)The optimal irrigation coefficient should be set to the bulk density of 1.34 g / cm3,the irrigation flow rate of 3.0L/ H,and the initial water rate of 7.0%,so that the maximum horizontal root range could be watered farther in the same infiltration time,and the plants with great lateral root developed grow better;The optimal irrigation coefficient should be set to the bulk density of 1.20 g / cm3,the irrigation flow rate of 3.0L/ H and the initial water rate of 7.0%,so that the maximum vertical root range could be watered deepest in the same infiltration time,and the plants with great vertical root developed grow better;The optimal irrigation coefficient should be set to the bulk density of 1.20 g / cm3,the irrigation flow rate of 3.0L/ Hand the initial water rate of 5.0%,so that the plant rootsfully absorb water in the same infiltration time;(5)Considering the advantages of the three dependent variables,like horizontal wetting front migration distance,vertical wetting front migration distance and soil water content after the 24 h distribution,the optimal irrigation coefficient should be set to the bulk density of 1.20 g / cm3,the irrigation flow rate of 3.0L/ H,and the initial water rate of7.0%,so that the moist body can cover more plant roots,which can fully absorb the water in the same infiltration time.