Quantification of soil macroporosity and its relationship with soil properties

Image analysis was used to estimate macroporosity (pores greater than or eq ual to 0.54 mm in diameter) of undisturbed soil columns obtained from a fie ld under no-till for 5 years. A high resolution x-ray Image Intensifier (XR II)-based CT scanner was used to investigate soil macroporosity at differen t depths in the soil column. Total macroporosity in the A and B horizons av eraged 3.70 and 1.94%, respectively, and was consistently lower in the B-ho rizon. The relative contributions of macroporosity to the total porosity in the A and B horizons were 7.76 and 4.92%, respectively. There was a statis tically significant decreasing trend of macroporosity through the combined A and B horizon depth (0-400 mm) and in the A horizon (depth 0-200 mm), but not in the B-horizon (depth 200-400 mm). Saturated hydraulic conductivity correlated significantly with the total macroporosity of the A and the B ho rizons, within the A horizon, bulk density also significantly correlating w ith total macroporosity.