Study On The Characteristics About The Transport Of Water And Nitrogen And Influential Factors Of Muddy Water Film Hole Free Infiltration

On the basis of reading and analyzing the relevant literature at home and abroad,combined with the reality of the muddy water irrigation in the Yellow River Basin in China,through the indoor and outdoor experiments and numerical simulation.The infiltration capacity,the wetting front migration distance,water and soil NO3-—N and NH4+—N distribution characteristics of the wetted body are mainly studied in view of the free infiltration of the muddy water film hole fertilizer.The following main research results have been achieved:(1)Under the conditions of different the fertilizer concentration,the film hole diameter,soil initial water content and muddy water content,the cumulative infiltration amount and infiltration time of the porous membrane pore area of the muddy water membrane conformed to the Kostiakov infiltration model.In the same infiltration time conditions,the infiltration coefficient K increased as concentration of fertilizer increased,but the infiltration coefficient K decreased as the initial water content,the film hole diameter and the sandy rate increased.An empirical model of cumulative infiltration volume and influencing factors and infiltration time was established and the reliability of the model was verified.(2)Under the conditions of different fertilizer concentration,membrane pore diameter,soil initial water content and muddy water content,the migration distance of the humid front increases with the increase of the concentration of fertilizer,the film hole diameter and the initial soil water content.On the contrary,it decreases with the increase of the sediment concentration in the muddy water.Meanwhile,under various influences,the wetting front migration process is a power function relationship.Indeed,an empirical model of the migration process of the wetting front under various influences is established respectively according to the power function.In the end,it is proved that the established empirical model is more reliable.(3)Under the conditions of different influence factors,the distribution of water content of soil moisture content in the humid body is half ellipse.With the distance from the center of the film hole near to the center,the water content contour line is from sparse to dense,the soil moisture content is the largest in the vicinity of the center of the film hole,and the water content is distributed contour is relatively loose,which is almost close to the saturated water content,and the water potential gradient is smaller,but the moisture content near the humid forward is changed greatly,the water content distribution contour line is more dense and the gradient of water potential is larger.In addition,in the same infiltration diachronic time,the higher the concentration of the fertilizer,the smaller the sediment concentration in the muddy water,the larger the initial water content and the diameter of the film pore,the greater the volume of the wetted body and the higher water content are obtained.The greater the corresponding water content is at the same position in the humid body.(4)Under the free infiltration condition of the muddy water film pore fertilizer,the measured wetted body level and the vertical soil content and content in the center of the film pore are greatly influenced by the concentration of the fertilizer,the diameter of the film pore,the sediment concentration of the muddy water and the soil initial water content when the water is stopped,and the end and redistribution of the water are 24 h and 48 h,and the soil and the main concentration are in the membrane.In the vicinity of the center of the hole,the measured soil and content near the wetting front have no obvious change,but the distribution of soil in the humid body is similar to that of the water distribution.With the increase of the concentration of the fertilizer,the decrease of the sediment concentration in the muddy water,the increase of the initial water content and the diameter of the membrane pore,the same infiltration diachronic and concentration fronts.The greater the migration distance,the higher the content and content in the same position in the humid body.(5)Hydrus-3D model was used to simulate the soil water movement characteristics of free infiltration of single film hole.The relative error between the simulated values and the measured values is compared and analyzed.Under the conditions of different initial water content,the relative error of the wet front migration process,the cumulative infiltration amount and the measured value of the vertical soil moisture content in the center of the membrane hole is smaller than the simulated value,that is the HYDRUS-3D model.It can well simulate the characteristics of soil water movement under the condition of free infiltration of muddy water with single film hole.