Microtomografia na caracterização do sistema poroso do solo sob integração lavoura- pecuária

Abstract

X-ray microtomography (MICRO-CT) analysis has proven to be a powerful tool in the study of porous systems in recent decades. There are numerous studies using MICRO-CT that analyze the properties of soil pores under different land uses. However, studies analyzing the effects of integrated systems at the micrometer scale are still scarce. The present study aims to analyze the effects of different soil management systems in a clayey Oxisol under integrated crop-livestock (ICL) integration. Samples were collected from the soil surface layer (0-0.20 m). The investigated treatments were: conventional tillage system (CT), minimum tillage system (MT), no-tillage system (NT), and no-tillage system with subsoiling (NT+S). In addition to the management systems, different uses of ryegrass were analyzed as cover crop (C), grazing (G), and silage (S). Soil samples were scanned using a MICRO-CT system with a voxel size of 50 μm. After scanning, the images were reconstructed in three dimensions (3D) for three distinct planes: coronal, sagittal, and axial. The properties analyzed by MICRO-CT were porosity, fractal dimension, degree of anisotropy, pore connectivity, tortuosity, and pore shape. This study is based on the following hypotheses: (i) ICL management systems affect the micromorphological properties of the soil; (ii) the use of vegetation cover improves soil porous system properties; (iii) different reconstruction planes do not affect the results of the analyzed properties. Soil tillage systems showed significant differences in soil morphological properties. MT(C) presented the highest values of assessed porosity, connectivity, volume, and number of rod-shaped pores, indicating a more favorable porous structure for water infiltration and redistribution processes. On the other hand, CT(S) presented the highest fractal dimension, the highest number of ellipsoidal-shaped pores, and a lower presence of spheroidal and disk-shaped pores, indicating a more complex porous system. NT(S) showed higher tortuosity and lower pore connectivity, indicating that the silage practice may negatively influence soil aeration and water transport. The degree of anisotropy and number of spheroidal and disk-shaped pores exhibited higher values for NT and NT+S systems, regardless of ryegrass use. However, overall, anisotropy was low, suggesting isotropic systems. No statistical differences were observed between treatments in terms of spheroidal and disk-shaped pore volumes, indicating greater resilience to changes in these shapes. Regarding the reconstruction planes (coronal, sagittal, and axial) of the images, no statistical differences were observed regarding the studied planes. However, it is suggested to use the plane that allows analyzing the largest volume of soil. This study provides an understanding of the micromorphological implications associated with different soil management practices, emphasizing that MT(C) appears to be the most suitable porous system.