A quantification of soil porosity using X-ray Computed Tomography of a Drummer silty clay loam soil

X-Ray Computed Tomography (X-ray CT) facilitates the quantification of soil structure by measuring soil macro-pore size, distribution, and porosity. An investigation of the effects of ultra-flex tires operating at low and standard tire inflation pressures on a silty clay loam soil prepared with three tillage systems (deep tillage, 450mm; shallow tillage, 100mm and no-till) on soil porosity using X-Ray Computed Tomography was conducted in the Molecular Imaging Laboratory at the Beckman Institute, University of Illinois at Urbana-Champaign, USA. The soil samples were collected from the treatments in a split-plot, factorial randomized complete block design field experiment with five blocks. In this experiment tire inflation pressure and tillage system were the main treatment plots and the trafficked locations, named highly trafficked (between crop row 3 and 4) and un-trafficked locations (between crop row 4 and 5), were considered as sub-plots. Sixty (60) undisturbed soil cores were collected from the highly trafficked and un-trafficked locations and CT scans of the cores at the spatial resolution of 98 µm were then conducted. The results of the X-ray CT scanning of soil showed that the low inflation pressure tire system had a significant benefit by maintaining a higher number of macropores (105.2, P = 0.010) and CT measured macro-porosity (4.66%, P = 0.004) as compared to the standard inflation pressure tire of macropores of 75.8 and CT measured macro-porosity of 2.87%. The mean number of pores and CT measured macro-porosity were 80.8% and 70.8% greater in the un-trafficked as compared to the highly trafficked locations. Adding the X-ray CT measured macroporosity to the field capacity porosity of the silty clay loam soil (39%) results in a total porosity that was similar to that derived by classical soil physics.