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Soil surface properties and infiltration response to crust forming of a sandy loam and silt loam
Soil and Tillage Research ( IF 6.1 ) Pub Date : 2025-01-04 , DOI: 10.1016/j.still.2024.106440
Lin Lin, Patric Yemeli Lonla, Jaianth Vijayakumar, Muhammad Khizar Khan, Gemmina Di Emidio, Nick Krekelbergh, Ann Verdoodt, Wim Cornelis

Soil surface crusting is a common phenomenon on agricultural soils susceptible to raindrop impact. Crusts affect soil hydrological properties, erosion, crop quality and yield, which implicates both agriculture and the environment. While methods for determining hydraulic or basic properties of thick soil layers are well established, measuring the soil characteristics of a thin crust still remains a challenge. In this study, we combined traditional lab methods and advanced techniques to reveal temporal variations of crust micro-morphology and their effect on soil properties with cumulative rainfall. Composite samples from two soil textures, a sandy loam and a silt loam, were collected and packed in soil pans, and exposed to a range of rainfall amounts and two rainfall intensities, using a laboratory nozzle-type rainulator. Intact soil ring samples were collected after each rainfall event. They were scanned using X-ray micro-computed Tomography (CT) to determine the evolution of soil porosity, bulk density and crust thickness during the crust formation process. The water permeability and infiltration dynamics of the developing crusts were investigated with minidisk infiltrometers placed on the crusts developed in the pans. Shear strength was evaluated by a hand vane. Disturbed soil was collected to explore variation in organic matter content and texture with cumulative rainfall. During the simulated rainfall events, soil loss, splash and runoff were recorded as well. We found that runoff volume and sediment mass increased, while splash and infiltration volume decreased with increasing rainfall amount. Shear strength increased until 200 mm of rainfall. Rainfall that resulted in crust formation had a rapid and strong effect on the hydraulic properties, with the unsaturated hydraulic conductivity being reduced as rainfall duration increased, and with high rainfall intensity having a greater impact than the low intensity. This was associated with rainfall-induced aggregate breakdown processes, which was confirmed by micro-CT. From the micro-CT images, we found that porosity reached a minimum value after 50 mm rainfall, while bulk density reached a maximum value. The dense crust was then partially removed/dissolved by further rainfall events. Crust thicknesses were about 3.19 and 4.85 mm, and the mean porosity of the crust layers was about 24 % and 27 % smaller than that of the underlying layer, at relatively high and low rainfall intensity, respectively. In conclusion, rainfall events significantly affect crust formation, on which the early-stage has the greatest influence. The crusts are rapidly formed under high rainfall intensity, but a thicker crust is formed under a longer duration of low rainfall intensity. The thickness of the crust increases with increasing rainfall, but its porosity does not decrease correspondingly.

中文翻译:


土壤表面特性和渗透对砂壤土和粉砂壤土结皮形成的响应



土壤表面结皮是易受雨滴影响的农业土壤的常见现象。结皮会影响土壤水文特性、侵蚀、作物质量和产量,这涉及农业和环境。虽然确定厚土层的水力或基本特性的方法已经很成熟,但测量薄壳的土壤特性仍然是一个挑战。在这项研究中,我们结合了传统的实验室方法和先进的技术,揭示了地壳微观形态的时间变化及其对累积降雨对土壤特性的影响。收集来自两种土壤质地(沙壤土和粉质壤土)的复合样品,并将其包装在土盘中,并使用实验室喷嘴式降雨器暴露在一系列降雨量和两种降雨强度下。每次降雨事件后收集完整的土壤环样本。使用 X 射线显微计算机断层扫描 (CT) 对它们进行扫描,以确定结皮形成过程中土壤孔隙度、体积密度和结皮厚度的演变。使用放置在锅中形成的结皮上的迷你盘渗透仪研究发育中的结皮的透水和渗透动力学。通过手向叶片评估剪切强度。收集受干扰的土壤以探索有机质含量和质地随累积降雨的变化。在模拟降雨事件期间,还记录了土壤流失、飞溅和径流。结果表明,随着降雨量的增加,径流量和泥沙质量增加,而飞溅和渗透量减少。抗剪强度增加,直到降雨量达到 200 毫米。 导致结壳形成的降雨对水力特性具有快速而强烈的影响,随着降雨持续时间的增加,非饱和水力传导率降低,高降雨强度比低强度的影响更大。这与降雨引起的骨料分解过程有关,这一点得到了显微 CT 的证实。从显微 CT 图像中,我们发现孔隙率在 50 mm 降雨后达到最小值,而堆积密度达到最大值。然后,致密的地壳被进一步的降雨事件部分去除/溶解。在相对较高和较低的降雨强度下,地壳厚度约为 3.19 和 4.85 mm,地壳层的平均孔隙度分别比下垫层小约 24 % 和 27 %。总之,降雨事件对地壳形成有显著影响,其中早期对地壳形成的影响最大。地壳在高降雨强度下迅速形成,但在较长时间的低降雨强度下会形成较厚的地壳。地壳的厚度随着降雨量的增加而增加,但其孔隙率并没有相应地降低。
更新日期:2025-01-04
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