涌泉根灌土壤水氮运移特性及其影响因素研究

发布时间：2018-03-14 02:42

本文选题：涌泉根灌　切入点：影响因素　出处：《西安理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：为了提高涌泉根灌水肥一体化灌溉条件下水分和氮素的利用效率,本文在室内通过人工配置不同肥液浓度、土壤初始含水率、土壤容重以及设置不同的灌水器间距水平,用土箱进行水肥入渗模拟试验。探究了各个影响因素对涌泉根灌入渗能力、湿润锋运移、土壤水分分布以及铵态氮和硝态氮运移特性的影响。取得的主要研究成果如下:(1)肥液浓度、土壤初始含水率、土壤容重和灌水器间距在涌泉根灌肥液入渗条件下的单位面积累积入渗量均与入渗时间吻合Kostiakov入渗模型。建立了以累积入渗量为因变量,入渗时间和各个影响因素为自变量的数学模型。累积入渗量伴随着肥液浓度的增大、初始含水率和土壤容重的减小而呈现出逐渐增大的趋势。涌泉根灌单向交汇条件下的累积入渗量较自由入渗小,且灌水器间距越小,相应的累积入渗量越小。(2)肥液浓度、土壤初始含水率以及土壤容重条件下,涌泉根灌肥液入渗各向湿润锋运移距离与入渗时间具有较为显著的幂函数关系;建立了以湿润锋运移距离为因变量,入渗时间和各个影响因素为自变量的湿润锋运移预测模型。经过验证,得到的模型具有较高的可靠性。同一入渗时刻条件下,各向湿润锋运移距离伴随着土壤容重的减小、土壤初始含水率和肥液浓度的增大而呈现出逐渐增大的趋势。伴随着灌水器间距的增大,灌水器位置处竖直向上、竖直向下的湿润锋运移距离均呈现出逐渐减小的趋势,均大于相同条件下的自由入渗;交汇界面处的湿润距离伴随着灌水器间距的增大而减小。灌水结束时刻,土壤容重越小、土壤初始含水率以及肥液浓度越大,灌水结束时刻湿润体内同一节点处的土壤水分含量相应的越大。随着再分布进行,湿润体范围变大,水分分布更加均匀。(3)涌泉根灌肥液入渗湿润体内铵态氮和硝态氮的分布受肥液浓度、初始含水率、土壤容重、灌水器间距以及时间和空间的影响。基于铵态氮特性,灌水结束及再分布阶段,铵态氮分布范围主要集中在灌水器出水孔附近土壤区域;对于硝态氮而言,基于其不易被土壤吸附易随水分运移的特性,其在湿润体内分布特性与水分相似。灌水结束时刻,湿润体内同一节点处的铵态氮、硝态氮质量分数随着土壤容重的减小、肥液浓度的增大而表现出增大的现象,湿润体内铵态氮和硝态氮平均值、变化量及变化率也均表现出与此相似的变化趋势。随着土壤容重的减小、肥液浓度、土壤初始含水率的增大,湿润体内硝态氮的分布区域变大。湿润体交汇界面同一节点处铵态氮、硝态氮质量分数均随着灌水器间距的减小而增大。湿润体内硝态氮质量分数在再分布3 d之内,平均值基本无变化,分布范围变大,变得较为均匀;再分布5 d直至再分布20 d,湿润体内铵态氮质量分数减小幅度较大;再分布20 d,湿润体内铵态氮含量接近土壤本底值;再分布5 d开始,硝态氮质量分数增幅较为显著,直至再分布15 d,湿润体内硝态氮含量基本达到最大值;再分布20 d开始,硝态氮含量低于再分布15 d,越接近土壤表层,硝态氮减少越缓慢。(4)在Hydrus-3D软件基础上对涌泉根灌条件下的水分入渗特性进行了相关模拟研究,并将模拟结果与实测值进行对比分析。表明Hydrus-3D软件可以很好的模拟涌泉根灌土壤水分入渗特性。
[Abstract]:In order to improve the utilization efficiency of bubble root irrigation irrigation and fertilizer integration of water and nitrogen, the chamber through the manual configuration of different fertilizer concentration, initial soil water content, soil bulk density and the emitter spacing set different levels of water and fertilizer with soil infiltration test box. To explore the impact of various factors on the surge root irrigation infiltration, wetting front and soil moisture distribution and the effect of ammonium nitrogen and nitrate nitrogen transport characteristics. The main results are as follows: (1) the fertilizer concentration, initial soil water content, soil bulk density and emitter spacing in bubble root irrigation fertilizer solution infiltration under the condition of the unit area of cumulative infiltration volume and infiltration time with Kostiakov infiltration model was established. The cumulative infiltration volume as the dependent variable, infiltration time and the impact of various factors as independent variables. The mathematical model of cumulative infiltration with fertilizer solution concentration. Large, reduce the initial water content and soil bulk density showed a gradually increasing trend. The cumulative bubble root irrigation under the condition of single line interference infiltration with free infiltration, and emitter spacing is small, the corresponding cumulative infiltration amount is smaller. (2) the fertilizer concentration, and soil bulk density the initial soil water content under bubbled root irrigation fertilizer solution infiltration anisotropic wetting front distance and infiltration time has a significant power function relationship with the dependent variable; a wetting front distance, infiltration time and the impact of various factors as independent variables of the wetting front movement prediction model. The model has been validated. High reliability. The same infiltration time under the condition of anisotropic wetting front distance is accompanied by a decrease in soil bulk density, increase the initial soil water content and fertilizer concentration and gradually increased. With the increase of emitter spacing, irrigation The water is at the position of the vertical, vertical wetting front distance decreased gradually, was greater than the free infiltration under the same conditions; interference interface wetting distance accompanied by the increase of the emitter spacing decreases. At the end of irrigation, soil bulk density is small, initial soil water content and fertilizer the liquid concentration, irrigating and soil moisture content in the same time moist nodes corresponding greater. With the re distribution, the wetting range becomes larger and more uniform distribution of water. (3) the bubbled root irrigation fertilizer solution infiltration wetting the distribution of ammonium nitrogen and nitrate nitrogen from fertilizer concentration the soil bulk density, initial water content, effect of emitter spacing and time and space. Based on the characteristics of ammonium nitrogen, and then the distribution stage end of irrigation, ammonium nitrogen distribution mainly concentrated in the soil near the emitter outlet for nitrate nitrogen; Speaking, it is not easy to be absorbed by soil characteristics with water transport based on the wetting characteristics and water distribution in irrigation is similar. At the end of ammonium nitrogen in wetting the same node, nitrate content decreased with the increase of soil bulk density, fertilizer concentration and increased with the phenomenon. The wetting of ammonium nitrogen and nitrate nitrogen average change quantity and change rate also showed the similar trends. With the decrease of soil bulk density, increase the fertilizer concentration, initial soil water content, the distribution of regional moisture nitrate becomes larger. Wetted the same node at the intersection of the interface ammonium nitrogen, nitrate nitrogen content was increased with the decreasing of emitter spacing. The wetting of nitrate content in distribution within 3 D, the average value of the fundamental change, the distribution scope of the change, become more uniform distribution; 5 d until the redistribution of 20 d Wetting, the ammonium nitrogen content decreased greatly; and the distribution of 20 D, the content of ammonium nitrogen in wet value close to the soil; then the distribution of 5 d, the mass fraction of the nitrate increased more significant, until the redistribution of 15 d. The content of nitrate nitrogen in wet basically reached the maximum value distribution; 20 D, the nitrate content was lower and distribution of 15 d, close to the soil surface, nitrate nitrogen decreased more slowly. (4) based on Hydrus-3D software for bubble root irrigation under the condition of water infiltration characteristics were related to simulation, and compared the simulation results with measured values showed that the Hydrus-3D software. Can be a good simulation of bubble root irrigation on soil water infiltration characteristics.

【学位授予单位】：西安理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S275

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