Soil pore characteristics assessed from X-ray micro-CT derived images and correlations to soil friability

X-ray computed tomography (CT) scanning technology has, in recent decades, been shown to be a very powerful technique to visualize and quantify soil structure. The objective of this project was to quantify soil pore characteristics, on undisturbed field moist soil, using a high resolution X-ray CT scanner and link then these results to soil friability assessed using the drop shatter method. Minimally disturbed soil cores were taken from selected treatments in a long-term rotation and tillage treatment experiment located on a silt loam at the Elora Research Station near Elora, Ontario, Canada. Soil cores varied in porosity and pore characteristics. A drop shatter test was used as a reference procedure to quantify soil friability. The top 40 mm of the 80 mm high soil samples were scanned using a X-ray micro-CT scanner. The selected region of interest (36 × 36 × 36 mm) was reconstructed with a voxel size of 60 μm. Estimated surface area, produced from the drop-shatter test, varied between 0.2 and 1.62 m2 kg− 1, and an average of 0.79 m2 kg− 1. Total and air-filled porosity was determined on the soil cores using traditional methods. Total porosity ranged from 41 to 60 m3 100 m− 3, and an average of 49 m3 100 m− 3. The air-filled porosity, at sampling/testing, ranged between 5 and 32 m3 100 m− 3, with an average of 15 m3 100 m− 3. The porosity determined from CT imagery ranged between 1 and 31 m3 100 m− 3, with an average of 4.5 m3 100 m− 3. The number of branches, junctions and end points averaged 298, 117 and 198 per cm3, respectively. We found significant and strong correlations between the soil pore characteristics assessed on the whole soil cores and the characteristics of the air-filled pores determined using high-resolution X-ray computer tomography (CT). Our study confirmed a significant correlation between soil friability, expressed by surface area produced by standardized drop-shatter, and soil pore characteristics. The strongest correlations were found with porosity, surface area and number of junctions per cm3.

► Quantification of soil pore characteristics using X-ray microCT scanning. ► Good correlation between pore characteristics assessed using different methods. ► Quantification of friability using drop-shatter test. ► Soil friability correlated well with soil pore characteristics.