| Moistube irrigation is a new invention of high-efficient on the basis of subsurface dripirrigation，this method can bring about irrigation of the whole growth cycle for crop.It usefunctional material semipermeable membrane as irrigation pipe，realize irrigation water tothe soil of crop root zone tardily by means of buried way, for uptake and utilization croproot. Compared with surface irrigation technology, moistube irrigation has manyadvantages, such as, water-saving effect is obvious, improving soil environment of rop rootzone，low running costs, strong anti-clogging performance. All of those can suitable cropwater demand in arid areas. The moistube irrigation flow approximates as line source,therefore，it’s also called Line Source Infiltration. Moistube irrigation is a passive way ofwater supply that depends on soil suction and driving force between internal and externalof semipermeable membrane，which is different with the conventional ground irrigation，drip irrigation from line source，vertical line source infiltration. Moistube irrigation as thenew irrigation technology，which was lack of complete irrigation experiment parameters.Experimental Study on Soil water movement during moistube irrigation is the premise andfoundation of designing moistube irrigation system properly and managing soil waterprecisely. In order to investigating the soil water movement and distribution of line sourceinfiltration under miostube-irrigation，this study had conducted soil box experiments fromline source in door. This paper had mainly analyzed the effect of the key factors soil texture,bulk density, initial soil water content and buried depth on the characteristic of wetted soil.It concluding wetting front migration pattern，soil water distribution in wetted soil andirrigation uniformity evaluation，test on relationship between irrigation amount withpressure head. The main results as follow：（1）The wetted soil looked like cylindrical object which with pipe as it’s axle centre and clay loam soil was approximate with cylinder, the cross section of sandy soil asobpyriform shape. The effects of the soil texture and bulk density on the characteristic ofwetted soil were significant in mois-tube irrigation. The volume of wetting body is affectedby soil texture，in the same irrigation time, wetting soil of clay loam soil is less than sandysignificantly. Moist body volume decreased with increasing bulk density, and with theextension of the irrigation time, difference gradually increases. We had fitted the predictionformula between volume of wetting body with bulk density，which error is small. Thediffusion coefficient of clay loam decreased with bulk density increasing，the Horizontal,vertical upward diffusion index equal to0.5approximately, which is less affected by bulkdensity.However, the diffusion index of downwards is influenced by bulk density clearlyand that increased with increasing of bulk density. The ratio of R: X: H was1:0.90:0.99inclay loam soil and1:0.81:0.95in sandy soil, respectively.(R: horizontal migrationdistance; X: vertical upward distance; H: vertical downward distance).(2) There was a typical power function relationship between the horizontal andvertical distance of wetting front and irrigation time. The diffusion coefficient of the sandyis bigger than clay loam, its diffusion index is less than clay loam soil. Miostube-irrigationhas small flow, which could automatically adjust with the change of soil water content,cumulative infiltration has a linear relation with irrigation time.R~2is much than0.9. Waterdistribution in the volume of wetted soil was a concentric circle with the pipe.Christiansten uniformity coefficient formula can be used for the irrigation uniformityevaluation under Moistube irrigation，there was no water saturated zone in wetted soil，most of soil water content lied between80%and90%of field capacity. Miostube-irrigationhas high irrigation uniformity, which reached85%. The effect of water saving ofmiostube-irrigation is prominent, which is suitable for crop water demand in the aridregions.（3）Initial water content had a great effect on line-source diffusion under moistubeirrigation, the advance rate of wetting front and surface wetting time increased with theraise of initial water content, and presented a power function relationship with theirrigation time. Meanwhile，the shape of wetting soil was lightly affected by initial watercontent the cross section of which is proximal circular. During an irrigation event, thecumulative infiltration and average infiltration rate were positively correlated with initial water content, while the time to reach stable infiltration rate was negatively correlatedwith it. The diffusion index of different directions by initial water content in soil moistureranging from0.50to0.60.The water inside wetting soil was concentrically distributed,and the moisture gradient decreased with the raise of initial water content, while irrigationuniformity of moistube-irrigation increased.（4）Moistube-irrigation was fitted the buried way，discharge and cumulativeinfiltration of buried moistube environ-grower were larger than the surface layingsignificantly. The Pressure head range within0~2.5m，amount and pressure head waslinear increasing trend. The changing process of infiltration with irrigation time wasaccorded with Kostiakov infiltration model, infiltration coefficient decreased with theincrease of buried depths and little change in infiltration index; Empirical formulabetween cumulative infiltration and buried depths was fitted，and the model was testedwith measured values, results show that the experimental equation of infiltration has ahigh correlation coefficient between the measured value and the calculated value.（5）Buried depths of miostube-belt had significant effect on the shape of wetted soil,horizontal migration distance and ratio of width to depth of γ decreased with the increaseof buried depths and vertical migration distance slightly increased with the increase ofburied depths; There was a significant different in vertical moisture distribution of moistsoil profile. Different buried depth lead to different migration regularity and uniformityof soil moisture in wetting front. The suitable buried depths of clay loam ofmiostube-irrigation were between15and20cm. |
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