This study aimed to investigate the effects of flow rate, initial soil moisture conditions and vermicompost (VC) application on total dissolved solids (TDS), nitrate (NO3), dissolved organic carbon (DOC) and colloid leaching from soil. Columns were filled with natural soil or VC-amended soil and were leached under unsaturated flow conditions using flow rates of 4.3–5.1, 2.5 and 0.4 mL/min. Two sets of experiments were conducted, one with the soils at initial air-dried conditions and the other with initial saturated conditions. Control experiments were conducted under saturated-flow conditions using flow rates of 2.7–3.8 mL/min for comparison. Results of the leaching experiments showed that EC, nitrate and DOC levels in the effluent were higher for the VC-amended soil versus the un-amended soil. Leaching under initial air-dried conditions and at the lowest flow rate (lowest water saturation) also produced higher EC, nitrate and DOC concentrations in the effluent. Conversely, effluent colloid concentrations were slightly higher for saturated-flow conditions, and elution behavior was similar between the un-amended and VC-amended soils. Statistical analysis revealed that the total leaching of TDS, nitrate, DOC and colloid under the initial air-dried conditions was not significantly different (p < 0.05) in comparison with the initial saturated conditions. Although, higher flow rates showed high amount of total leaching of TDS, nitrate, DOC and colloid, unsaturated flow rate of 2.5 mL/min leached more efficiently than flow rate of 2.7–4.3 mL/min in un-amended soil. Findings of this study would help decision makers to better manage soil salinity, drainage and groundwater pollution. Particularly, applying lower flow rates for irrigation applications to maintain unsaturated conditions can significantly decrease colloid migration and soil erosion.

本研究旨在研究流速、初始土壤湿度条件和蚯蚓堆肥 (VC) 施用对总溶解固体 (TDS)、硝酸盐 (NO3)、溶解有机碳 (DOC) 和胶体从土壤中浸出的影响。用天然土壤或 VC 改性土壤填充柱子，并在不饱和流动条件下使用 4.3–5.1、2.5 和 0.4 mL/min 的流速浸出。进行了两组实验，一组在初始风干条件下使用土壤，另一组在初始饱和条件下进行。对照实验在饱和流条件下进行，流速为 2.7–3.8 mL/min 以进行比较。浸出实验的结果表明，与未改性土壤相比，VC 改性土壤的流出物中 EC、硝酸盐和 DOC 水平更高。在初始风干条件下和最低流速（最低水饱和度）下的浸出也会在流出物中产生更高的 EC、硝酸盐和 DOC 浓度。相反，在饱和流条件下，流出物胶体浓度略高，未改性和 VC 改性土壤的洗脱行为相似。统计分析表明，与初始饱和条件相比，初始风干条件下 TDS、硝酸盐、DOC 和胶体的总浸出没有显着差异（p < 0.05）。尽管较高的流速显示 TDS、硝酸盐、DOC 和胶体的总浸出量较高，但在未修正的土壤中，2.5 mL/min 的不饱和流速比 2.7-4.3 mL/min 的流速更有效。这项研究的结果将帮助决策者更好地管理土壤盐分、排水和地下水污染。特别是，在灌溉应用中应用较低的流速以保持不饱和条件可以显着减少胶体迁移和土壤侵蚀。