Quantifying Pore Network Differences Between Cohesive and Non-Cohesive Soils via X-ray CT and Hydraulic Measurements

Abstract This study aimed to evaluate whether parameters obtained by X-ray Computed Tomography (CT), differentiate cohesive from non-cohesive horizons, and establish their relationship with soil hydro-physical properties. The study was conducted on Acrisols and Lixisols from northeastern Brazil, comparing cohesive and non-cohesive horizons of each soil profile. Undisturbed samples were collected to evaluate the pore network by X-ray CT and determine saturated hydraulic conductivity ( K sat ) (among these samples, 5 were collected horizontally and 5 were collected vertically), soil water retention curve, and soil aggregate stability. All cohesive horizons had higher values of micropores, ultramicropores, and cryptopores compared with non-cohesive horizons, except for the soil from Cruz das Almas (BA), which showed the opposite result. Mean weight diameter and aggregate/clod stability reveal a tendency for aggregates to be larger and more stable in cohesive horizons. The cohesive horizons of the Fortaleza (CE) and Goiana (PE) soils showed lower K sat , greater pore tortuosity, higher Euler number (indicating lower pore system connectivity), and higher frequency of pores in the 80-1000 µm range in relation to the non-cohesive horizons. The soil from Cruz das Almas (BA) showed no differences between the cohesive and non-cohesive horizons with regard to pore morphology evaluated by X-ray CT. Soil K sat was related negatively to almost all pore morphology parameters obtained by X-ray CT. Rendered images of the isolated pore volume revealed a striking visual difference, with cohesive horizons showing more isolated pores compared with non-cohesive horizons, except for the Cruz das Almas soil.