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

Abstract 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 m 2  kg − 1 , and an average of 0.79 m 2  kg − 1 . Total and air-filled porosity was determined on the soil cores using traditional methods. Total porosity ranged from 41 to 60 m 3  100 m − 3 , and an average of 49 m 3  100 m − 3 . The air-filled porosity, at sampling/testing, ranged between 5 and 32 m 3  100 m − 3 , with an average of 15 m 3  100 m − 3 . The porosity determined from CT imagery ranged between 1 and 31 m 3  100 m − 3 , with an average of 4.5 m 3  100 m − 3 . The number of branches, junctions and end points averaged 298, 117 and 198 per cm 3 , 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 cm 3 .

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