The Study On Soil Solute Transport Characteristics And The Key Technologies Of Drip Irrigation In Red Soil

The application of water and fertilizer integration irrigation technology is increasingly applied to the irrigation of cash crops in the hilly red soil region of southern China in recently.Taking the example of navel orange in the southern region of Jiangxi Province,in recent years,the region has vigorously implemented the efficient water-saving renovation project for economic crops such as navel orange citrus.The drip irrigation technology is mostly applied to navel orange irrigation in hilly areas.That the study on the technical parameters of drip irrigation suitable for the region played an important guiding role in the design and implementation of navel orange and citrus drip irrigation in this region.Using the method that is a combination of experimental and theoretical analysis,we concluded moisture solute transport rule with different bulky density which are in vertical and horizontal states.Besides,wealso measured related parameters of water solute migration that are required in modeling process.Through indoor and field experiments,the content of water and the content of NO3--N in the wet body were studied under the influence of multi-source drip irrigation,and the wet wetting front and moisture solute distribution were simulated with commercial software Hydrus-3D.On this basis,we evaluate the navel orange drip irrigation project designed and implemented based on the test results by Analytic Hierarchy Process and Fuzzy Comprehensive Evaluation.The main conclusions are as follows:(1)The bulk density has a strong influence on the soil water characteristic curve of red soil.Under the same water content,the bulk density of red soil is larger,and the soil suction is larger,showing a power function relationship.The bulk density has a great influence on the distribution of red soil solutes and infiltration capacity.The larger the bulk density is,the smaller the infiltration capacity is,and the more obvious the water blocking effect is,the less water solute can penetrate into the deep soil.Non-adsorbed ion migrates with water in red soil,and there is a significant redistribution process after infiltration.The concentration of infiltration solution has a great influence on the infiltration process of red soil.The concentration had a great influence on the infiltration ability of red soil.HYDRUS can simulate the distribution of water movement and solute migration in one-dimensional infiltration of red soil under the influence of different factors.The average relative error between simulated and measured values is within 10%.(2)After the single-point source infiltration test,the wetted body showed a semi-ellipsoidal shape.The larger the bulk density,the greater the horizontal distance of the wet front was in the vertical direction.The larger the volumetric load under the same flow conditions,the more obvious the water accumulation on the surface.The multi-points source intersection infiltration under the influence of multiple factors has a great influence on the intersection time.The larger the spacing,the longer the convergence time of the wet front.The smaller the distance between the dripper,the larger the flow rate is,the more likely it is to cause the occurrence and development of the accumulated water and surface runoff.When the flow rate is 8.4mL/min(2L/h),the horizontal velocity of the wet front and the distance are greater than the vertical direction.Moreover,the soil structure changes due to water immersion within 10 cm below the surface,and NO3--N enrichment reaches a maximum in this range.The maximum average error of the simulated and inductive values of the Hydrus-3D model under different factors is 11.5%.The simulation accuracy of the wetting front is the highest,and the simulation accuracy of the NO3--N migration distribution is the worst.According to the comprehensive analysis,when the bulk density is 1.4 g/cm3 under indoor test conditions,the distance between the drip heads of multi-points source drip irrigation in red soil area is 40 cm,and the dripper flow rate is 4.2 mL/min(1 L/h).(3)Field trials in red soil hilly areas showed that after the infiltration and infiltration,the larger the spacing,the wider the wetting range;when the spacing was the same,the flow rate was 2 L/h,the wetted body was the largest,the spacing was 20 cm,and the flow rate was 2 L/h.The intersection area is the largest.The flow rate and spacing of the dripper have a great influence on the distribution of water and solute transport.When the flow rate is 2 L/h,the water content and NO3--N in the range of 20 cm below the surface of the four different spacing tests are higher.The simulation error of the field test Hydrus-3D model reached 13.5%;the model efficiency coefficient was above 0.85,indicating that the model has good reliability.(4)The post-evaluation system of the umbilical orange drip irrigation water-saving reconstruction project was established by the analytic hierarchy process-fuzzy comprehensive evaluation method.The comprehensive evaluation scores of the four irrigation districts designed and implemented according to the test interval were:bamboo back is 3.6548,Lingbei is 3.335,Huangkeng is 3.007,Daxianbei is 2.9744.The evaluation of drip irrigation and water saving project in Zhubei Village Navel Orange Irrigation District was excellent,and the other three irrigation districts were good;it indicated that the drip irrigation technical parameters obtained by the experiment were the best parameters suitable for production.The most suitable flow rate for multi-points source drip irrigation in the red soil hilly region was 1 L/h,and the distance between the drip heads was 40 cm.