2D and 3D techniques to assess the structure and porosity of Oxisols and their correlations with other soil properties

Structure and porous geometry are dynamic soil parameters that control several soil processes and functions. This study details the differences in the structure of typical Oxisols regarding the clay amount, biological activity, and mineralogy. Combining 2D and 3D image analysis can provide detailed information about the soil structure and porous system. The objectives of this study were: (i) to describe the soil microstructure and degree of microaggregation; (ii) to quantify porosity, soil pore types, and soil pore size distribution using 2D and 3D techniques; and (iii) to better understand the relationship between the porous system and the biological, chemical, mineralogical, and physical properties of the soil. The study considered four Oxisols: Xantic Kandiustox (P1), Rhodic Haplustox (P2), Anionic Acrustox (P3), and Typic Hapludox (P4). The results showed that all Oxisols have some degree of microaggregation. The Rhodic Haplustox (P2) had the most pronounced degree of microaggregation, which reflects the greater biological activity and gibbsite/kaolinite ratio, and lower hematite/(hematite + goethite) ratio compared to the other Oxisols. The pore types found by 2D analysis were complex pores in P1 and P2 and rounded pores in P3 and P4. The 3D analysis showed that P2 and P3 have a more connected porous system compared to the other Oxisols, evidenced by the lower value of the Euler number. The best connectivity values of the porous system were congruent to improved saturated hydraulic conductivity measured in a separate sample set.

Automated summary

This study investigated the structure and porous system of four Oxisols by combining 2D and 3D image analysis. The results showed differences in microaggregation and pore types among the soil types, with Rhodic Haplustox exhibiting the most pronounced degree of microaggregation. The connectivity of the porous system was found to be related to the saturated hydraulic conductivity of the soils.