Two-dimensional Infiltration Water And Solute Transer Characteristic And Numerical Simulation In Furrow Irrigation

Furrow irrigation is widely used in intertilled crop irrigation technology.After years of research and development,the management and design level of the furrow irrigation system has been improved to some extent,but the inefficient use of water and fertilizer is still the main problem at present.Based on this,using a combination of experimental research,numerical simulation and theoretical analysis,the water migration and nitrogen transfer characteristics of two-dimensional infiltration in furrow irrigation were studied,and the following main conclusions were obtained:(1)Sandy soil and clay loam in Yangling area were selected as typical soils.The soil shrinkage characteristics during the soil water characteristic curve determination by centrifuge method were analyzed.The contraction process was described by the three-linear model,and the numerical simulation method was used to analyze the soil shrinkage characteristics.The rationality of the hydraulic characteristic parameters obtained under the two scenarios of weight change and weight change is not taken into account.The results show that the three-linear model can describe the soil shrinkage characteristics in the process of determining the soil water characteristic curve with the centrifuge method,and the hydraulic characteristic parameters estimated under the condition of changing the soil bulk density are more reasonable,which can significantly improve the furrow irrigation water numerical simulation accuracy.(2)The water movement model of two-dimensional infiltration in furrow irrigation was established by HYDRUS software,and the water movement process was simulated.The simulation results were validated by indoor experiments and the effects of different factors on infiltration characteristics of furrow irrigation were analyzed.The results showed that the simulated values of soil water content and cumulative infiltration in the wetland had a high consistency with the measured values,indicating that the model can be used to simulate the two-dimensional infiltration process in furrow irrigation;the soil texture and the bulk density are important for the furrow irrigation process.The effects of cumulative infiltration and wet front are all significant,and the depth of water in the trench has a significant effect on cumulative infiltration,but the change in depth in the trench only has a greater impact on the horizontal wetting front and has little impact on the vertical direction;soil initial Moisture content has a greater impact on the migration velocity of the wet front,but it has a relatively small effect on cumulative infiltration.(3)The numerical simulation method was used to invert the soil hydraulic parameters under different KNO3 concentrations,and the combined water and fertilizer transport process of influent irrigation was simulated.The results showed that the distribution of NO3--N was similar to the distribution of water,showing the characteristics of easy movement with water,while K+ was mainly distributed near the irrigation ditch.The initial soil moisture content,bulk density,depth of water in the ditch and other factors affected the distribution of K+.Both are small,but the effect of soil texture on K+ distribution is greater than other factors.(4)By comparing the infiltration characteristics of different KNO3 solution concentration and clean water in furrow irrigation,it was found that the coupling of water and fertilizer is conducive to soil infiltration,and can increase the average moisture content in the wet body,and establish a calculation model and humidification of cumulative infiltration capacity under the condition of water and fertilizer coupling.Forward migration model.The nutrient redistribution was simulated by HYDRUS software.It was found that the nitrate nitrogen has a higher risk of deep leakage during the redistribution process.In this study,the models were all based on the assumption that soil homogenization,water,and nutrients were uniformly distributed in the soil,ignoring the influence of other factors(priority flow,layered soil,plant,etc.)on water and fertilizer transport.In addition,the soil texture used in this paper is relatively simple.The results obtained from other soil textures are applicable for further study.At the same time,the concentration of fertilizer solution set in the experiment is not large and there are only 3 gradients.The solute is infiltrated by the soil.Whether the effect will have a peak at a certain concentration also requires further study.