Soil Water And Nitrogen Transport Characteristics Experiment Andsimulation Under Film Hole Infiltration

On the basis of literature review on film hole irrigation, nitrogen fertilizer transport and transformation in soils worldwides, considering irrigation and fertilization practice in China, this research involves laboratory studies, theoretical analyses and simulation with an emphasis on the laboratory tests. This dissertation covers researches on soil water and nitrogen transport characteristics under film hole infiltration with fertilization. The main findings are as follows:(1) Water and nitrogen transport characteristics and coupled movement characteristics of soil water and nitrogen under single point source film hole fertilizer solution infiltration were studied. Fertilizer solution infiltration can increase capacity as compared with demineralied water. Infiltration quantity and wetting depth increased with increased solution concentration at the same depth, soil water content and NO₃^-3-N concentration also increased. Models for infiltration quantity and wetting front transport under different concentration of film hole infiltration were established in this study. Subsection models for soil NO₃^-3-N with wetting depth in vertical soil at film hole center were established. The concentration of NO₃^-3-N had a"S"shape correlation with soil water content. Subsection models for the correlation of soil NO₃^-3-N and water content in vertical soil at film hole center were established. Soil NH4 + ?N content mainly lies in the 5cm scope of surface layer.(2) Water and nitrogen transport characteristics under film hole fertilizer solution single-line interference infiltration were studied. Film hole fertilizer solution single-line interference infiltration can decreased infiltration capacity as compared with single point source film hole fertilizer solution infiltration. Wetting front transport rate of interference center is bigger than the rate of film hole center, vertical and horizontal wetting front transport distance of interference interface had a power function with time. The concentration front transport distance of NO₃^-3-N in soil profile increased with the increased solution concentration and the NO₃^-3-Nconcentration also increased with time at the process of water supply. Four mathematical models for film hole fertilizer solution single-line interference infiltration were presented based on different measured data, the calculation precision of the four infiltration models are accurate through the measured data.(3) The influence factors on soil water and nitrogen transport characteristics under film hole single-lineinterference infiltration were researched. Analyzed the correlation between the single point source infiltration, vertical 1 dimension infiltration and film hole single-line interference infiltration, so single point source infiltration parameters and film hole single-line interference infiltration parameters can be determined according to vertical 1 dimension infiltration parameters. Wetting front and soil NO₃^-3-N front transport distance increased with increased film hole diameter and initial soil water content, decreased with increased soil density and film hole space. Functions correlation of water content and soil NO₃^-3-N with wetting depth in vertical soil at film hole center and interference center under different film hole diameter were established. Soil texture had obvious influence on soil water content and NO₃^-3-N distribution. The influende of fertilizer application on soil water is little, but the influence on soil NO₃^-3-N distribution is biggish.(4) Coupled movement characteristics of soil water and nitrogen under film hole fertilizer solution single-line interference infiltration were studied with different solution concentration. Infiltration quantity and wetting front distance increased with increased solution concentration. Models for infiltration quantity and wetting front transport with different solution concentration under film hole single-line interference infiltration were established. Wetting depth and concentration front of NO₃^-3-N increased with increased solution concentration. Soil water content and NO₃^-3-Ncontent also increased with increased solution concentration at the same depth and the same time. Subsection models for soil NO₃^-3-N with wetting depth in vertical soil at film hole center and interference center and the models for the correlation of soil NO₃^-3-N and water content were established.(5) Water and nitrogen transport characteristics under film hole fertilizer solution bilateral interference infiltration were studied. Wetting front transport distance had a power function with time. At this paper experiment conditions, soil water and NO₃^-3-N in vertical soil of film hole center and interference center have the same distribution laws at the 10cm and 8cm scope of soil surface layer respectively, the distribution grads of soil water and NO₃^-3-N of film hole center and interference center below the 10cm and 8cm scope of soil surface layer are different, the sequence is:later interference center >earlier interference center > film hole center. The sequence of water content and NO₃^-3-N content at the same depth and the sequence of wetting depth under different film hole infiltration type is:single point source film hole infiltration < single-line interference infiltration 3^-3-N concentration front transport distance increased with increased film hole diameter and initial soil water content, decreased with increased soil density and film hole space. Soil texture had obvious influence on soil water content and NO₃^-3-N distribution. Influence of fertilizer application on infiltrationquantity content and wetting front transport distance and soil water content is less, and the influence on soil NO₃^-3-N distribution is biggish. The soil NO₃^-3-N content under fertifation mainly lies in the surface layer and the NO₃^-3-N content was preserved in shallow soil easily. The distribution of soil NO₃^-3-N under surface and deep application concentrated in the 7¹2cm scope below soil surface.(7) Coupled movement characteristics of soil water and nitrogen under film hole fertilizer solution bilateral interference infiltration were studied. Infiltration quantity and wetting front transport distance increased with increased solution concentration. Models for infiltration quantity and wetting front transport distance with different solution concentration under film hole single-line interference infiltration were established. The soil water content increased with increased solution concentration at the same depth and the same time. At this paper experiment conditions, soil water content in vertical film hole center and interference center have the same distribution laws and the distribution relatively even at the 10cm scope of soil surface layer, the distribution grads of soil water in film hole center and interference center below the 10cm scope of soil surface layer are different, the sequence is:later interference center >earlier interference center > film hole center. Soil NO₃^-3-N content in vertical soil of film hole center and earlier interference center at the 12.5cm scope of soil surface layer and later interference center at the 10 cm scope soil surface layer have the same distribution laws and the distribution relatively even, the distribution grads of NO₃^-3-N in film hole center and earlier interference center below 12.5cm and later interference center below 10cm are bigger, the grads increased with increased fertilizer solution concentration. Subsection models for soil NO₃^-3-N with wetting depth in vertical soil at film hole center and interference center were established.(8) The model for simulating the movement of water and NO₃^-3-N under single point source film hole fertilizer solution infiltration was developed. The commercial software HYDRUS-2D was used to simulate water and nitrogen transport in the soil. The simulated results agreed well with measured data.