Water And Salt Transport Characteristic Under Moistube Irrigation

Moistube irrigation is a kind of continuous irrigation technique, through theground belt way, using the membrane water potential difference as a driving force,driving water slowly to the crop root zone. Due to their remarkable water-savingeffect, low energy consumption, in recent years began to get used in agriculturalproduction. While the most widely used of drip irrigation technology, due to itscharacteristics of intermittent irrigation, soil evaporation and salt leaching exist at thesame time, salt distribution-desalting process repeatedly, cannot keep the crop rootzone completely state of desalination, and has certain negative influence on cropgrowth and development. In turn，Moistube irrigation is a kind of continuousirrigation methods, because of its characteristics of ground belt way，Soil evaporationis weak. When it used on saline-alkali land, not only can ensure the whole growthperiod of crop water requirement, and can be kept moist soil layer in a state ofdesalination. And thus the investigation of the rule of soil water and salt transportunder the condition of moistube irrigation is the precondition of correct use of thisnew type of irrigation. In order to explore the rule of soil water and salt transportunder different influencing factors of moistube irrigation, this experiment has carriedon the laboratory simulation experiment and greenhouse cultivation experiment. Thisexperiment mainly analyzes the mineralization degrees, pressure head and infiltrationwater amount on soil water and salt migration regularity and micro embellish theinfluence of irrigation on the impact of greenhouse tomato growth and water useefficiency. The main research conclusions are as follows：（1）Degree of mineralization has small impact on the shapes of soil wetted zone, wetting front shape were similar to circle. Degree of mineralization has relativelybigger influence on the volume of wetted soil.The volume of wetted soil inmineralized water was bigger than that in pure water.The wetting front (horizontal,vertical up and down) migration distance of3g/L is farthest,the wetting frontmigration distance has power function relationship with time. The mineralized watercan increase cumulative infiltration.However the relationship between cumulativeinfiltration and degree of mineralization was not linear relationship.The cumulativeinfiltration and average soil moisture content of3g/L is biggest.The results of thisstudy provide reference for the utilization of moistube-irrigation with mineralizedwater. When salinity is lower than3g/L, the infiltration of water has certain leachingon soil salt content. When mineralization degree the increased further, the infiltrationof water for salt leaching with a smaller role. Using brackish water for short-termirrigation, there were no significant differences between distilled water treatment andbrackish water treatment for average soil salt content.(2) Cumulative infiltration was positively correlated with the hydraulic head;infiltration of buried way is greater than the surface, while establishing a higheraccuracy mode to predict cumulative infiltration. Wetting front distance increases withincreasing hydraulic head, cross-section of wet body are similar to "round" and theinitial rapid rate of wetting front, the latter gradually slow down. Soil moisturemaximum values were close to the moistube and the greater the hydraulic head, thewider the range of soil moisture distribution, the average soil moisture content ishigher. The distribution of soil salt under different hydraulic head presents formoistube with axis, the characteristics of the trend of increasing. The same depth ofsoil salt content and pressure head are obvious negative correlation. With the increaseof the hydraulic head, the cut in reducing zone depth of growth of salt.(3) The wetting front transport distance and infiltration water is power functionrelationship; With the increase of infiltration water amount, the same depth of soilmoisture content increased; The amount of infiltration water is small, the watercontent of soil profile curve is relatively flat, Along with the infiltration of watercontinues to increase, the water content of soil profile curve after first steep and gentlechange characteristic; Soil salinity in moistube as the center outward gradually increased. And with the increase of water infiltration, soil desalting depth anddesalting efficiency also increase gradually, but the desalting depth is not significant.The salt of wetting front with the infiltration water increased exponentially. Each soilsalt content below5cm of the plane of the moistube is lower than the initial saltcontent. Infiltration of water quantity, the more soil desalting effect is obvious. Theaverage soil salt content of0to10cm is higher than the initial salt content under themoist depth of15cm, when the infiltration water continues to increase,0to10cmsoil layer soil performance for desalination.(4) Drip irrigation soil moisture dynamics frequently than moistube irrigation,moistube irrigation can adjust itself according to water demand of plants. From theperspective of plant height and stem diameter, moistube irrigation is more conduciveto plant growth. Meanwhile two treatments tomato photosynthetic rate variation wassimilar to bimodal curve, leaf transpiration rate and stomata conductance showed asingle peak curve；Both yields per unit area or water use efficiency, moistubeirrigation is better than drip irrigation; Water consumption laws are similar betweentwo irrigation methods, but the water demand of drip irrigation is bigger thanmoistube irrigation.