Assessment of hydro-physical properties of some crusting soils in four different soil form as revealed by micro-focus x-ray computed tomography in Limpopo Province, South Africa

Abstract

Most of the available knowledge about soil structure degradation through crust formation is limited to two-dimensional geometry. However, soil is a natural three-dimension body. The objective of the study is to assess soil crusting and hydro physical properties in four different soil form by using X-ray Computed Tomography, Characterizing micro-morphometric of crusting soil’s pore system, quantifying soil structure degradation through crusting development and visualizing hydro physical properties in all four-soil form. Micro X-ray Computed Tomography techniques can greatly add value to existing knowledge because they can reveal soil structure in three dimensions (3D). Undisturbed soil aggregates were obtained from two adjacent sampling locations namely Visibly Crusted (VC) and Not-Visibly Crusted (NVC). Four soil forms were studied in Limpopo province, South Africa at Vhembe Region under Thulamela and Collin Chabane local Municipality. Soil form studied are Dundee, located at (Tshamutoro village), Shortlands (Mukula Village), Hutton (University of Venda) and Glenrosa (Ha-Davhana village). The samples were scanned using Nikon XTH 225L micro-focus CT X-ray unit. The scans were reconstructed into three-dimensional volume data set of pore shapes, pore size and porosity among the soils using CT Pro software® and further analysed using VG Studio Max V3.0®. images were acquired after 30 minutes in each scan. The result of the study indicated that total porosity decreases with increase in depth, and the shape of the aggregates were dominated by regular pores that are susceptible to water erosion. Moreover, soil pores inform of mesopores, micropores, and macro pores were recorded using 3D images acquired .By visualizing hydro physical properties using images in 2D and 3D, it was possible to visualize arrangement of aggregates and their sizes helping to understand the erodibility of soil. In conclusion X-ray computed tomography is an effective tool to study the microstructure of soil aggregates.