3D-visualization and quantification of soil porous structure using X-ray micro-tomography scanning under native pasture and crop-livestock systems

Abstract

Integrated crop-livestock system (ICLS) is expected to improve the soil structure and porosity, yet the studies quantifying the effect of ICLS on soil porosity is still limited. This study evaluated the long-term effect of on-farm integration of cover crops and livestock in the croplands converted from the native pasture on soil pore characteristics. The croplands included a traditionally used corn (Zea mays L.)-soybean (Glycine max (L.) Merr.) rotation of the region, referred as control, CNT and corn-soybean-cover crops with livestock grazing of corn and soybean residues and cover crops, referred as integrated crop-livestock system, ICLS. The native pasture (NP) was utilized as baseline to assess management induced changes in soil properties. Three intact soil core samples were collected from each land use - CNT, ICLS and NP. X-ray computed microtomography (μCT) at a resolution of 31.6 µm was used to assess soil pore structural parameters under all the three land uses. We found that CT- derived porosity was higher in NP (12.8%) and ICLS (8.2%) compared to the CNT (4.3%). Fractal dimension was higher in NP (2.5) compared to ICLS (2.4) and CNT (2.3). Soils under CNT had larger values of degree of anisotropy and tortuosity as compared to the NP and ICLS. The pores > 10 mm3 had the largest contribution to porosity, and these pores were significantly higher in ICLS than the CNT. Triaxial shaped pores occupied a bigger fraction of porosity and number of pores for all the treatments. Results of this study indicate that long-term adoption of ICLS improves soil pore properties which would enhance soil functional process and have positive implications for nutrient cycling, root growth, soil gas fluxes and water dynamics.