X-ray computed tomography - Measured pore characteristics and hydro-physical properties of soil profile as influenced by long-term tillage and rotation systems

Soil hydro-physical properties and pore characteristics are crucial for crop production as they determine water, air, and nutrients transfer. Long-term tillage and crop rotation studies provide valuable insights into the effects of management practices on various soil properties. Because of the inherent differences between the surface and sub-surface soils, the impact of management systems can be pronounced differently at different soil depths. Though many studies have reported the tillage and rotation effects on soil hydro-physical properties, their vertical impacts to a depth of 40 cm were less explored. This study aims to assess the impact of long-term tillage and crop rotations on soil hydro-physical properties and pore characteristics to a depth of 40 cm utilizing the Xray Computed Tomography (XCT) technique. Intact soil cores of 7.6 cm height x 7.6 cm null were collected from tillage [no-till (NT); reduced-till (RT); conventional-till (CT)] and crop rotation [continuous corn (CC) - Zea mays L. and corn-soybean (CS) - Glycine max [Merr.] L.] plots of 0-40 cm depth (each sample for 10 cm increment). The XCT scanning allowed us to investigate the soil pore size distribution, porosity, number of branches, and average branch length. Measured hydro-physical properties in the study include bulk density (rho b), plant available water content (PAW), saturated hydraulic conductivity (Ksat), and water retention. XCT image analysis revealed that NT with CC/CS rotation increased the number of macropores at surface and sub-surface depths. However, the number of mesopores was higher with NT x CS. In addition, NT lowered the rho b by 9.6 % and increased the PAW by 28 % compared to the CT. Ksat was higher under NT x CS at 0-10 cm and had a strong positive correlation with the XCT-measured number of macropores. Therefore, we conclude that NT with CS rotation can potentially improve soil pore characteristics and hydro-physical properties, leading to enhanced soil function.