Grassland Conversion To Croplands Impacted Soil Pore Parameters Measured Via X-Ray Computed Tomography

Soil porosity estimated conventionally cannot provide the spatial distribution and geometrical properties of pore networks. This on-farm study assessed the impacts of grassland-cropland conversion on soil pore characteristics. This study aimed to quantify the microscale changes in pores near the soil surface (0-10 cm) under grasslands converted to croplands managed with a rotation of corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] (CS); an integrated crop-livestock system (ICLS) of corn-soybean-oats (Avena sativa L.)-cover crops (CCs), with livestock grazing on corn and soybean residue after harvest and on CCs; and the native grassland (NG). Intact soil cores (diameter: 76.2 mm; length: 76.2 mm) were collected in three replications from CS, ICLS, and NG areas located adjacent to each other. Soil cores were scanned via X-ray computed tomography (CT) (pixel resolution: 0.226 by 0.226 mm; slice thickness: 0.5 mm). Soils under CS converted from NG significantly decreased CT-measured macroporosity eightfold. However, it increased sevenfold when CS was converted to ICLS. Higher connected porosity, connection probability, and macroporosity under ICLS and NG enhanced the saturated hydraulic conductivity (K-sat) compared with CS. The soil organic carbon (SOC) stock was increased by 13% at 0- to 10-cm depth, when soils under CS were converted to improved management (ICLS). Significant correlations of CT-measured pore parameters were found with K-sat. We conclude that CS converted from grasslands degraded SOC, pores, and other hydro-physical properties, which can be enhanced by integrating CCs and grazing on CCs and crop residues.