Conservation agriculture is increasingly preferred to conventional methods due to its benefits in promoting more sustainable soil management. Our study aims to compare physical and morphological properties, at the microscale, of soils under long-term no tillage (NT) and minimum-tillage (MT) to adjacent ‘natural’ soils under long-term secondary forest (SF). Soil aggregates of c. 2 cm length were imaged by X-ray Computed Tomography (XCT). The three-dimensional (3D) images were segmented and analyzed in order to assess properties such as porosity, number of pores, degree of anisotropy, pore shape, volume classifications, Euler number for pore connectivity, and pore tortuosity. The pore architecture of soils under NT and MT, for c. 40 years, was similar to that from the SF in terms of imaged porosity, pore size, and shape distributions, as hypothesized in our study. However, we observed some important differences; for instance, SF had larger, more connected, and more complex pores, likely due to the greater biological activity. In addition, SF had more isotropic pores than NT and MT, i.e., without preferential flow paths for water redistribution. Therefore, we concluded that long-term conservation agriculture was efficient at reversing structural damage typically associated with conventional, intensive agriculture, but some large differences remain, particularly concerning the pore network complexity and connectivity.

Soils are dynamic and complex systems in their natural state, which are subjected to profound changes due to management. Additionally, agricultural soils are continuously exposed to wetting and drying (W-D) cycles, which can cause modifications in the complexity of their pores. Thus, we explore how successive W-D cycles can affect the pore network of an Oxisol under contrasting managements (conventional tillage—CT, minimum tillage—MT, no tillage—NT, and secondary forest—F). The complexity of the soil pore architecture was evaluated using a 3D multifractal approach combined with lacunarity, Shannon’s entropy, and pore geometric parameters. Our results showed that the multifractal approach effectively identified and quantified the changes produced in the soil pore architecture by the W-D cycles. The lacunarity curves revealed important aspects of the modifications generated by these cycles. Samples under F, NT, and MT suffered the most significant changes. Pore connectivity and tortuosity were largely affected by the cycles in F and NT. Our findings demonstrated that the 3D geometric parameters and normalized Shannon’s entropy are complementary types of analysis. According to the adopted management, they allowed us to separate the soil into two groups according to their similarities (F and NT; CT and MT).