摘要:优先流是土壤水分入渗的一个重要途径, 大孔隙是产生优先流的关键因素。研究优先流对于土壤水分和溶质运移研究及生态环境保护、制定合理的田间管理措施等具有重要意义。本研究将田间亮蓝染色示踪试验和WHCNS (soil water heat carbon nitrogen simulator)模型模拟相结合, 研究了华北平原冬小麦-夏玉米轮作体系存在大孔隙下, 强降雨和不同施肥、灌溉情景下土壤水氮运移的情况, 以此探讨大孔隙优先流对于土体中水分和硝态氮运移的影响。结果表明:明显含有虫洞的免耕土壤入渗深度和染色面积均高于旋耕土壤; 免耕土壤的染色面积和稳定入渗速率的Pearson相关性不显著, 染色示踪不能定量化土壤稳定入渗速率。同时WHCNS模拟的0~100 cm土层硝态氮淋洗量结果显示:一方面, 相较于无大孔隙情景, 大孔隙存在会显著增加硝态氮的淋洗量; 另一方面, 大孔隙存在下优化施肥模式的硝态氮淋洗量比传统施肥模式减少46.0%。常规灌溉量下喷灌比漫灌处理的硝态氮淋洗量减少15.6%;强降雨导致硝态氮淋洗量增加119.4%。本研究为华北平原地区大孔隙存在条件下的农田水肥优化管理措施提供了理论指导。
关键词:优先流/
水分入渗/
染色示踪/
WHCNS模型/
氮素淋洗
Abstract:Preferential flow is an important mechanism that relies on macropores for moisture to infiltrate into soil. Understanding this process affects the study of soil moisture, solute transport, and environmental protections for field management practices. In this study, a brilliant blue staining tracer field experiment and the soil water heat carbon nitrogen simulator (WHCNS) model were used to explore the effects of preferential flow of macropores on soil water transport and nitrate nitrogen leaching. The WHCNS model was used to simulate soil water and nitrogen migration through macropores in a North China Plain winter wheat-summer maize rotation field with heavy rainfall, fertilization, and irrigation. A dyeing tracer was used to follow water infiltration into no-tillage and rotary-tillage soil, and Pearson correlation coefficient analysis was performed on the stained area and the no-tillage soil stable infiltration rate. The results showed that the no-tillage soil infiltration depth and dyeing area were higher than that of the rotary-tillage soil. The no-tillage soil had a deeper dyeing depth, reaching 80–100 cm, while that of rotary-tillage was shallow, reaching only 15–20 cm. The no-tillage soil had a high degree of preferential flow and transported moisture to the deep-soil. There was no correlation between the no-tillage soil dyeing area and the stable infiltration rate (P = 0.68). Therefore, dye tracers cannot quantify the soil stable infiltration rate. At the same time, the WHCNS simulation results of nitrate nitrogen leaching in 0–100 cm soil layer showed that the presence of macropores increased the nitrate nitrogen leaching in both traditional and optimal fertilization modes, compared with no macropores. On the other hand, in the presence of macropores, optimized fertilization reduced nitrate nitrogen leaching by 46.0% compared with that in traditional fertilization. The sprinkler irrigation reduced leaching by 15.6% compared with that in conventional flood irrigation, and heavy rainfall increased leaching by 119.4%. If the farmland has macropores, organic fertilizer and sprinkler irrigation may be used to save water and reduce nitrate nitrogen leaching; however, increased leaching is expected during heavy rainfall. Therefore, climatic conditions should be considered when fertilizing to determine suitable irrigation amounts. This study used a field tracing experiment and WHCNS model simulation to demonstrate that preferential flow can increase soil water infiltration and nitrate nitrogen downward movement and provides guidance for optimizing farmland water and fertilizer management with macropores in the North China Plain.
Key words:Preferential flow/
Water infiltration/
Dye tracer/
WHCNS model/
Nitrogen leaching
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