Temporal and spatial variability in 3D soil macropore characteristics determined using X-ray computed tomography

Authors: BUDHATHOKI, SUMAN - Auburn University; LAMBA, JASMEET - Auburn University; SRIVASTAVA, PUNEET - University Of Maryland; MALHOTRA, KRITIKA - Auburn University; Way, Thomas - Tom; KATUWAL, SHEELA - University Of Arkansas

Submitted to: Journal of Soils and Sediments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/26/2022
Publication Date: 2/11/2022
Citation: Budhathoki, S., Lamba, J., Srivastava, P., Malhotra, K., Way, T.R., Katuwal, S. 2022. Temporal and spatial variability in 3D soil macropore characteristics determined using X-ray computed tomography. Journal of Soils and Sediments. 22:1263-1277. https://doi.org/10.1007/s11368-022-03150-x.
DOI: https://doi.org/10.1007/s11368-022-03150-x

Interpretive Summary: The flow of water through soil is important for providing infiltration to deliver rain and irrigation water to crop roots, and for reducing runoff water. However, this flow can have detrimental environmental effects, as it allows nutrients and other solutes to be transported by subsurface water flow away from the field area to which they are applied. X-ray computed tomography scans which are CT scans used in medicine, were used for measuring pores in soil and for determining the connectivity of soil pores. At a downslope location on a pasture, the soil had relatively few pores in the surface soil layer, compared to an upslope location. Results are expected to be useful in determining soil characteristics and conducting computer modeling, to minimize water quality degradation of streams, rivers, lakes, and other waterbodies.

Technical Abstract: The influence of soil macropores on the transport of water and solutes in subsurface flows has long been known. Preferential flow via soil macropores can have a large effect on water quality. Hence, it is important to quantify soil macropore characteristics to better understand preferential flow behavior in soils. Currently, little information exists on the changes in soil macroporosity in response to topographical position within a field and how macropore characteristics change temporally within a field. Therefore, the objective of this study was to use X-ray computed tomography (CT) and image analysis to quantify temporal and spatial variability in 3D soil macropore structure in a 0.40 ha pasture field. A total of 36 undisturbed soil columns, 150 mm in diameter and 500 mm in length, were collected during May and September of 2019. The macropore characteristics differed significantly between different topographical positions and sampling seasons, especially at the surface (0-100 mm) depth. The soil macropores at the downslope position were sparsely distributed in the surface soil layer. This was attributed to a relatively higher degree of grazing-induced compaction due to higher soil moisture at the downslope position, as compared to the upslope locations. In contrast, dense macropore networks were observed at the downslope positions for depths greater than 250 mm. The results of this study provide quantitative information on 3D soil macropore characteristics under varying topographical locations and time in a pasture field.