Abstract. Monitoring soil structure is of paramount importance due to its key role in the critical zone as the foundation of terrestrial life. Variations in the arrangement of soil components significantly influence its hydro-mechanical properties, and therefore its impact on the surrounding ecosystem. In this context, soil compaction resulting from inappropriate agricultural practices not only affects soil ecological functions, but also decreases the water-use efficiency of plants by reducing porosity and increasing water loss through superficial runoff and enhanced evaporation. In this study, we compared the ability of electric and electromagnetic geophysical methods, i.e. Electrical Resistivity Tomography and Frequency-domain Electromagnetic Method, to assess the effects of compaction on agricultural soil. The objective was to highlight the electro-magnetic response caused by both heavy plastic soil deformations generated by a super-heavy vehicle and the more common tractor tramlines. DC-current prospecting has finer spatial resolution and allows a tomographic approach, requiring higher logistic demands and the need for ground galvanic contact. On the other hand, contactless electromagnetic induction methods can be quickly used to define the distribution of electrical conductivity in the shallow subsoil in an easier way. Results, validated with traditional soil characterization techniques (i.e. penetration resistance, bulk density and volumetric water content on collected samples), show the pros & cons of both techniques and how differences in their spatial resolution heavily influence the ability to characterize compacted areas with good confidence. This work aims at contributing to the methodological optimization of agro-geophysical acquisitions and data processing, in order to obtain accurate soil models through a non-invasive approach.

中文翻译：

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用于土壤压实评估的电磁和直流地球物理学


摘要。监测土壤结构至关重要，因为它在作为陆地生命基础的关键区域中发挥着关键作用。土壤成分排列的变化显着影响其水力力学特性，从而影响周围生态系统。在这种情况下，不适当的农业做法导致的土壤板结不仅影响土壤生态功能，而且还通过减少孔隙度并通过表面径流和蒸发增加而增加水分流失，从而降低植物的水分利用效率。在这项研究中，我们比较了电和电磁地球物理方法（即电阻率断层扫描和频域电磁法）评估压实对农业土壤影响的能力。目的是强调超重型车辆和更常见的拖拉机有轨电车线路产生的重塑性土壤变形引起的电磁响应。直流电勘探具有更精细的空间分辨率，并允许采用断层扫描方法，需要更高的后勤要求和地面电接触。另一方面，非接触式电磁感应方法可以快速地以更简单的方式定义浅层土中的电导率分布。使用传统土壤表征技术（即收集样品的渗透阻力、容重和体积含水量）进行验证的结果显示了这两种技术的优缺点，以及它们空间分辨率的差异如何严重影响以良好的置信度表征压实区域的能力。 这项工作旨在促进农业地球物理采集和数据处理的方法优化，以便通过非侵入性方法获得准确的土壤模型。