Evaluating Soil Tillage Practices Using X-Ray Computed Tomography and Conventional Laboratory Methods

Using x-ray computed tomography (CT) for non-destructive 3-D imaging and analysis of soil physical properties has been investigated for over 30 years. However, applying this system in soil science has remained a specialized research area using primarily low-resolution medical-grade x-ray CT units that were not designed for soil analysis applications. The main research objectives were to characterize and compare physical properties of soil core samples from long-term chisel plow (CP) and no-till (NT) agricultural field management sites using a high-resolution industrial-grade x-ray CT unit and two conventional soil laboratory method (SLM) soil macroporosity analysis procedures. Field research activities during 1999 included collecting four soil columns for each CP and NT soil management practice at the Iowa State University Northeast Research and Demonstration Farm at Nashua, Iowa. Findings from this study indicate that percent macroporosity and soil bulk density values were significantly higher and lower, respectively, for annual CP rowcrop (corn and soybean) versus annual NT rowcrop systems. Since the soil structure of perennial NT vegetation (native grasses and trees) is similar to CP, rowcrop practices could explain inconsistent soil hydraulic conductivity values from NT cropping systems. These results underscore the potential of x-ray CT as an effective soil porosity analysis tool and suggest the development of an online database of x-ray CT 3-D soil core images based on soil type and tillage system. This readily available information could aid scientists in soil structural analysis applications, potentially avoiding the limitations of x-ray CT unit cost and system availability issues.

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