Revealing soil hydraulic parameters via X–ray tomography depends on the relationship between soil pore structure and saturated hydraulic conductivity

Changshu City, Jiangsu Province, China. Quantification of pore morphological parameters by X–ray tomography coupled with hydrological characteristic analysis can reveal the characteristic differences in water and solute leaching and transport among different land uses in plain river networks. The soil pore characteristics were analyzed by tomography (CT) image scanning, and the water conductivity and holding capacity were determined. The interrelationships between pore structure and hydraulic properties of rice–wheat rotation and pear orchard fields were also discussed. New hydrological insights for the region: Soil pore diameters in the whole profile of the two land uses were concentrated in the ranges of 0.55–2 and 0.55–4 mm, respectively. The degree of anisotropy was distributed between 0.22 and 0.39, which means high spatial variation in two fields. The CT–identified porosity within 0–30 cm layer of pear orchard field was 3.5 times higher than that of rice–wheat rotation field. The soil saturated hydraulic conductivity ( K s ) was positively correlated with > 0.25 mm aggregate, connectivity density, fractal dimension, and CT–identified porosity and negatively correlated with bulk density. K s was mainly affected by soil pore characteristics. Alternating drying–wetting conditions and frequent tillage result in low porosity and low water conductivity in surface layer, demonstrating high water retention. This study is conducive to further research on water movement and groundwater pollutants migration of regional agricultural. X-ray tomography revealing soil hydraulic parameters depends on the relationship of soil pore structure and saturated conductivity. • Soil pore morphological and hydraulic properties were analyzed simultaneously. • Soil pore structure directly affected the hydraulic properties. • K s was improved through changing soil pore structure. • Pore structure had more variations under two land uses than hydraulic properties.