【作者】 康银红；

【导师】 马耀光；

【作者基本信息】 西北农林科技大学 ， 农业水土工程， 2006， 硕士

【摘要】 氮肥的施用,提高了农作物的产量,解决了世界粮食的需求问题,但也带来了一系列的环境问题。随着人口地不断增长,一方面需要继续提高作物产量,另一方面又须防止由于化肥施用量过高和施用方式不当而引起的生态环境破坏和环境污染。解决这些问题的关键技术之一是综合调控土壤——作物——超根层系统中的水分和养分的分布、运移、贮存、转化过程以及相应的生态效应,确定合理的施肥量和灌水量,达到增产、节约水肥资源、保护环境质量的目的。本文在灌溉条件下,讨论施入氮肥后对黄土超根层中NO₃^- -N的分布和运移的影响,确定灌水量对氮淋失的影响关系,较为准确地预测土壤和地下水的氮污染状况。主要结论如下:（1）10m深度黄土范围内,土壤含水量的变化与黄土岩性、灌溉水量以及气候有关。在受天气影响显著的2.0m以内,土壤含水量波动较大;在2.0m深度以下,含钙质结核古土壤层的基质势比黄土层的大,致使水分在古土壤层中聚集,并在1.0～3.4m,7.2⁸.0m深处出现两个显著的含水量峰值带。（2）黄土层在水分集中补给条件下,渗流过程表现为明显的湿润峰值带的移动,宽度约2.4m。集中的灌溉补给,在黄土层中形成二元非饱和渗流。微孔隙渗流的水分峰值带运移速率约5⁶.5mm/d,黄土垂直裂隙及大孔洞中存在优先流,其运移速率可达450mm/d以上。（3）NO₃^- -N在施肥灌溉及作物吸收的综合影响下形成峰值带,浓度随深度增加逐渐减小,平均运移速率为56.3mm/d。说明在包气带黄土层对入渗水流及携载的NO3—N产生沿程吸收,具有显著的滞留和蓄存作用。（4）NO₃^- -N浓度在土壤表层随时间的变化明显,随着深度的增加,变化越来越趋于平稳。上层土壤中NO₃^- -N被大量淋洗到深层土壤并得到了累积,不但造成资源的大量浪费,而且成为地下水污染源。（5）水分通量的总体变化趋势是由地表随深度的增加逐渐减少,在土壤深度上具有明显的分带特征。氮素通量在黄土层的不同深度上的分布存在明显的淋失区和吸附区。水分通量在深度上的分布存在明显的拐点,而氮素通量则没有拐点。（6）土壤表面蒸发强度与取样时间呈对数关系。在试验期间,土壤表面蒸发强度为0.25～2.66%。水分和NO₃^- -N湿润峰的推移速率与灌溉定额均呈对数关系。水分渗漏率与灌水定额呈幂函数关系,NO₃^- -N淋失率与灌水定额则呈指数函数关系。更多还原

【Abstract】 The use of nitrogen fertilizer improves the crop quantity and meets the present demand for the food in the world. However, it brings a series of environmental problems. With the increase of population, on the one hand, we need to continue improving crop productivity; on the other hand, we must avoid destroying and polluting the ecological environment effected by high fertilizer use volume and improper using method. One key technique to solve these problems is to integrated regulate the distributing, motivation, storage and translation of water and nutrition in the soil—crop—aerated zone system and its ecological effect, and determine the reasonable fertilization and irrigation in order to get the aim of improve quantity, save water and fertilizer, and improve the environmental quality. This paper discusses the irrigation effect on the NO₃^- -N distribution and motivation in the aerated Loess Plateau, ascertain the relationship between irrigation and nitrogen leaching, and precisely predict the polluted condition of soil and groundwater. After analyzing, we got the conclusions as follows:（1）The soil moisture content changes with Loess lithology, irrigation quantity and local climate in 10m-scope depth. It changes prominently in 2m scopes, which are effected by the weather condition. In 2m deeper depths, matrix potential energy in ancient soil is larger than that in yellow soil, so the soil moisture is collected in ancient soil. There are two notably peak value strips in 1.0³.4m and 7.2⁸.0m depth.（2）Under concentrate water supply, the seepage process has prominent motivation of high soil moisture content, and its width is about 2.4m. The unsaturated irrigation supply has duality in yellow soil. The mini-pore water velocity is 5⁶.5mm/d while the preferential flow velocity can reach 450mm/d.（3）NO₃^- -N has the peak value strip under the synthesized effect of fertilizer, irrigation, and crop absorption. The concentration reduced with the depth increasing, its average velocity is 56.3mm/d. It shows that ancient and loam soil in yellow aerated zone has prominent retention and storage of seepage water.（4）NO₃^- -N concentration is apparent in upper soil. With the depth deeper, it changes mildly. Most of the NO₃^- -N is eluted to the deeper soil and got collected. It goes on moving更多还原