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Assessing the influence of the rhizosphere on soil hydraulic properties using X-ray computed tomography and numerical modelling

Daly, Keith R.; Mooney, Sacha J.; Bennett, Malcolm J.; Crout, Neil M.J.; Roose, Tiina; Tracy, Saoirse R.


Keith R. Daly

Professor of Soil Physics

Interim Pro-Vice Chancellor For Research & Knowledge Exchange

Tiina Roose

Saoirse R. Tracy


© 2015 © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology. Understanding the dynamics of water distribution in soil is crucial for enhancing our knowledge of managing soil and water resources. The application of X-ray computed tomography (CT) to the plant and soil sciences is now well established. However, few studies have utilized the technique for visualizing water in soil pore spaces. Here this method is utilized to visualize the water in soil in situ and in three-dimensions at successive reductive matric potentials in bulk and rhizosphere soil. The measurements are combined with numerical modelling to determine the unsaturated hydraulic conductivity, providing a complete picture of the hydraulic properties of the soil. The technique was performed on soil cores that were sampled adjacent to established roots (rhizosphere soil) and from soil that had not been influenced by roots (bulk soil). A water release curve was obtained for the different soil types using measurements of their pore geometries derived from CT imaging and verified using conventional methods, such as pressure plates. The water, soil, and air phases from the images were segmented and quantified using image analysis. The water release characteristics obtained for the contrasting soils showed clear differences in hydraulic properties between rhizosphere and bulk soil, especially in clay soil. The data suggest that soils influenced by roots (rhizosphere soil) are less porous due to increased aggregation when compared with bulk soil. The information and insights obtained on the hydraulic properties of rhizosphere and bulk soil will enhance our understanding of rhizosphere biophysics and improve current water uptake models.


Daly, K. R., Mooney, S. J., Bennett, M. J., Crout, N. M., Roose, T., & Tracy, S. R. (2015). Assessing the influence of the rhizosphere on soil hydraulic properties using X-ray computed tomography and numerical modelling. Journal of Experimental Botany, 66(8), 2305-2314.

Journal Article Type Article
Acceptance Date Nov 25, 2014
Online Publication Date Mar 4, 2015
Publication Date 2015-04
Deposit Date Mar 9, 2017
Publicly Available Date Mar 9, 2017
Journal Journal of Experimental Botany
Print ISSN 0022-0957
Electronic ISSN 1460-2431
Publisher Oxford University Press
Peer Reviewed Peer Reviewed
Volume 66
Issue 8
Pages 2305-2314
Keywords Bulk soil, image-based homogenization, matric potential, rhizosphere, soil pores, water release characteristic, X-ray computed tomography
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