Reduced tillage practices, including no-till, have been proposed to reduce NO₃^- leaching in agricultural soils. However, this is not universally supported by experimental data, and the effect of reduced tillage on NO₃^- leaching is likely connected to the interaction between macropore flow and resident solutes. To investigate this, we carried out infiltration experiments on intact soil cores from conventionally tilled (CT) and no-till (NT) plots, recording resident concentrations and breakthrough curves (BTCs) of three solutes (a tritium pulse, resident Br^- tracer and native NO₃^-). We then fitted a dual porosity model implemented in HYDRUS-1D, to the experimental BTCs. By assuming different initial solute distributions between phases, we investigate possible bypass mechanisms. In the lysimeter experiment, leaching of all solutes initiated and peaked earlier in NT compared to CT, indicating increased macropore flow. However, total leached NO₃^- was greater in CT, and higher resident NO₃^- concentrations were found after the experiment in NT, suggesting an overall bypass effect. In the fitted dual porosity model, saturated water contents in the mobile phase were six times smaller in NT than in CT, with smaller horizontal solute transfer rates for NO₃^- than for Br^-. The optimal initial proportion of total resident NO₃^- in the mobile phase was 7.5% in NT and 65% in CT. Our results suggest a bypass effect of native resident NO₃^- in NT soils related to a smaller volume of soil involved in macropore flow. Added solutes, however, remain susceptible to quicker leaching in NT compared to CT under intense precipitation.

已经提出减少耕作的做法，包括免耕，以减少农业土壤中的 NO ₃ ^-浸出。然而，这并没有得到实验数据的普遍支持，减少耕作对 NO ₃ ^-浸出的影响可能与大孔流动和驻留溶质之间的相互作用有关。为了研究这一点，我们对传统耕作 (CT) 和免耕 (NT) 地块的完整土壤芯进行了渗透实验，记录了三种溶质（氚脉冲、常驻溴^示踪剂和原生 NO ₃ ^-）。然后，我们将在 HYDRUS-1D 中实施的双孔隙度模型拟合到实验 BTC。通过假设相之间不同的初始溶质分布，我们研究了可能的旁路机制。在蒸渗仪实验中，与 CT 相比，NT 中所有溶质的浸出开始并达到峰值更早，表明大孔流量增加。然而，在 CT 中总浸出的 NO ₃ ^-更大，在 NT 实验后发现更高的常驻 NO ₃ ^{-浓度，表明存在整体旁路效应。}在拟合的双孔隙度模型中，流动相中的饱和水含量在 NT 中比在 CT 中小 6 倍，NO ₃ ^-的水平溶质转移率比 Br ^-小. 流动相中总驻留 NO ₃ ^-的最佳初始比例在 NT 中为 7.5%，在 CT 中为 65%。我们的研究结果表明，NT 土壤中原生居民 NO ₃^的旁路效应与参与大孔隙流动的土壤体积较小有关。然而，在强降水下，与 CT 相比，添加的溶质仍然容易在 NT 中更快地浸出。