Hydraulic Characteristics Of Emitter In Soil Of Subsurface Drip Irrigation System

Subsurface drip irrigation (SDI) has been generally considered as the most development water saving irrigation technique. Study on dripper's hydraulic characteristics and soil-water movement of SDI has important points in its reasonable design. Based on the SDI testing system, the hydraulic properties of emitter were studied. Main research results are shown as follows:1. Testing system of single emitter in SDI was established. The system provides pressure using water tank and pump together in order to satisfy requires of different experiments. Moreover, it can measure the weight changing of barrel which emitter is buried in to measure the changing course of emitter's drainage by using the system of data collecting and processing based on strain gages load cell.2. Quadratic regression equation which is used to express the relationship between discharge of SDI emitter and pressure, buried depth and initial soil water content was built by using regression circumvolving testing method. The result shows that the drainage of emitter is highly interrelated with pressure.3. Indoor experiments show that the drainage of SDI emitter is basically steady and have no clear changing with time. The drainage of SDI drippers is smaller than the surface drip irrigation (DI) drippers.4. Program of soil-water movement was compiled using ADI based on the existing mathematical model of soil-water movement for SDI. Indoor experiments have been carried out to verify the rationality of the model.5. A new method obtaining the soil hydrodynamics parameters is developed.The experiment scheme is made by using regression circumvolving testing method. Quadratic equation used to express the relationship between sum of D-value square of simulating soil water content and measuring one and the soil hydrodynamics parameters was established by using mathematical model of soil-water movement for SDI. It can find the optimal parameters fitting the soil property by quadratic plan method which can seek the minimum value of sum of D-value square. This process provides a new thought for obtaining the soil hydrodynamicsparameters.6. The rules of Soil -water movement were analyzed when irrigation design parameters alter. Soil texture, irrigation lasting time, emitter discharge rate, the depth emitter is buried and initial soil water content have great influence on soil-water distribution, so these factors should be considered in SDI design.