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为了探讨在优先流影响下农地土壤水分与溶质的运移规律,以昌平农地土壤为研究对象,通过原状土取样和分层填充制备实验土柱,模拟存在优先流和平衡入渗2种水分下渗过程,分析优先流对农地土壤中硝态氮运移的影响。结果表明:相较于平衡入渗,存在优先流的土壤中硝态氮运移的速率更快、数量更多,且其穿透曲线表现出拖尾现象。优先流的存在会使土壤的水分出流速率达到平衡入渗过程的1.48～2.69倍,且波动程度较大;受其影响,硝态氮运移表现出快速、大量下渗的特征,原状土柱中NO3-的穿透时间为12 h,此时的孔隙体积为0.36,相较于填充土柱分别减少了57%和27%。此外,原状土柱中以NO3-标记的优先流占水流总量的43.83%,引起的NO3-累计淋出量占总量的97.60%,这表明有限的优先流流量能够引起绝大部分的硝态氮运移。土壤优先流还使得其穿透曲线表现出拖尾现象,这可能是由于优先流和基质流之间下渗速率的不平衡造成的。
In order to explore the law of soil moisture and solute transport under the influence of preferential flow, taking Changping farmland soil as the research object, two kinds of preferential flow and balanced infiltration were simulated through sampling and stratification of undisturbed soil. The process of water infiltration was analyzed to analyze the effect of preferential flow on the migration of nitrate nitrogen in agricultural soil. The results show that nitrate-N transport in soil with preferential flow rate is faster and more abundant than that under balanced infiltration, and its breakthrough curve shows trailing phenomenon. The existence of preferential flow can make the soil water outflow rate reach to 1.48 ~ 2.69 times of infiltration equilibrium process, and the degree of fluctuation is greater; under the influence of it, the nitrate nitrogen transport shows the characteristics of rapid and massive infiltration, The breakthrough time of NO3- in the column was 12 h, and the pore volume at this time was 0.36, which was reduced by 57% and 27% respectively compared with the filled column. In addition, the NO3-labeled preferential flow in the intact soil column accounts for 43.83% of the total water flow, and the NO3-cumulated leachate is 97.60% of the total, indicating that the limited preferential flow can cause most of the NO Nitrogen transport. The soil preferential flow also caused its traversing curve to show trailing phenomena, possibly due to the imbalance of the infiltration rate between the preferential flow and the matrix flow.