Water And Nitrogen Transport And Translation Characteristics Research And Numerical Simulation Under Film Hole Free Infiltration

Based on the related literature on the theory and technique of film hole infiltration from the home and abroad, linked with the national physical science fund item"nitrogen transport characteristics and appraisal method on irrigation quality research under fertilization farmland by the film hole infiltration",this paper use laboratory test ,theoretical analysis and numerical simulation as the technical line ,research the water and nitrogen transport and translation characteristics under film hole infiltration and set up numerical simulation model .the main results were shown as followllings:(1) Doing the experimental study on soil NH₄⁺ - N transport and translation charateristic under the film hole fertilizer fluid free infiltration. The results show that the soil NH₄⁺ - N transports slowly ,because of the adsorption of soil colloid to the NH₄⁺ - N, the NH₄⁺ - N envidencely lags to soil water transport , NH₄⁺ - N mainly accumulates in the soil near the film hole center; Nitrogen content measure results find that two weekes after Irrigation and fertilization,the soil NH₄⁺ - N loses 68 percent,the main reason is NH₄⁺ - N transformation.(2) Doing the experimental study on soil NO₃^- - N transport and translation charateristic under the film hole fertilizer fluid free infiltration. The results show that soil NO₃^- - N transport charateristic is similar with the soil water ,influenced by the convection-dispersion equation. Distribution range of NO₃^- - N is similar with the soil wetted volume, its transport charateristics holds coherence with soil water; But distribution of NO₃^- - N has its own charateristic ,next to the film hole the content is very large and almost keep the same value ,beyond this range,the content of NO₃^- - N quikly reduce from this value to soil background value.In redistribution process,the soil water in humid region is tend to homogenizing,but the content of NO₃^- - N keeps relative stability near the film hole center in 200 hours after water supply,except the content has some change near the wetting front.(3)Doing the research on film hole free infiltration charateristics of urea by laboratory test.The results are followings:under the film hole free infiltration ,the transport charateristic of urea molecule influenced by the convection-dispersion equation keeps same with the soil water .the soil colloid has adsorption to urea molecule, so the urea transport is blocked,suggest that urea content is high near the film hole; Hydrolysis rate of urea is quick in soil, hydrolysis and nitration of urea in soil finished in 15 days under experimental condition; Non-fertilization and deep application of fertilizer has no envidence effect on infiltration rate and capacity,irrigation and ferterlization infiltration capacity a little more than deep application of fertilizer, surface application of film hole infiltration capacity is evidencely larger than others, wetted depth of surface application is evidencely larger than others,except nearby wetting front,the soil moisture content is same in same wetted depth under different fertilization.(4)Buliding numerical simulation of soil water movement and soil NO3-N transport ,use ADI format Gauess—Seidelbinding with iteration method to solve the model, meantime the computed result is validated by model experiment,the result show that the simulated value is agreed with the measured value.