Abstract: The aim of this study was to articulate the potential of medical computed tomographic (CT) scanning for analyzing soil structure (macroporosity, soil matrix density, number of macropores) and how these estimates compare with, and complement, traditional laboratory measurements (bulk density, total porosity, effective air-filled porosity, and air permeability). Undisturbed soil cores were sampled at two depths (0.35 and 0.7 m) in a long-term soil compaction experiment in southern Sweden 14 years after its establishment. Persistence of subsoil compaction was detectable by CT-estimated soil matrix density, bulk density, and total porosity. Vertical distribution of CT-estimated air-filled macroporosity between 0.25- and 0.45-m depth showed that biological activity effect on macroporosity was largest in the top of the soil columns from the compacted plots, whereas reduction of macroporosity was significant at the bottom of the same columns. This was not detectable by classical laboratory measurements. Variations in air permeability could be related to the CT-estimated number of pores but not to the CT-estimated air-filled macroporosity. Despite using a coarse resolution, the combination of visualization and traditional laboratory measurements proved valuable in identifying the persistent effects of subsoil compaction and the differences in soil structure among the two investigated subsoil layers. However, we recommend to systematically perform a sensitivity analysis to the segmentation threshold before any further analysis of CT-estimated parameters.
1Department of Agroecology, Aarhus University, Tjele, Denmark.
2School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR.
3Visualization Sciences Group, an FEI Company, Houston, TX.
4Department of Biotechnology, Aalborg University, Aalborg, Denmark.
5Agroscope Research Station ART, Department of Natural Resources and Agriculture, Zürich, Switzerland.
6Swedish University of Agricultural Sciences, Department of Soil and Environment, Uppsala, Sweden.
7Department of Nuclear Medicine and PET-Centre, Aarhus University Hospital, Aarhus, Denmark.
Address for correspondence: Dr. Mathieu Lamandé, Aarhus University, Blichers Allé 20, P.O. Box 50, DK-8830 Tjele, Denmark. E-mail: firstname.lastname@example.org
Financial Disclosures/Conflicts of Interest: This work is part of a Scandinavian cooperation on the effects of subsoil compaction on soil functions ( www.poseidon-nordic.dk). The study was financed in part by the international project Soil Infrastructure, Interfaces, and Translocation Processes in Inner Space (Soil-It-Is) funded by the Danish Research Council for Technology and Production Sciences and in part by the Danish Ministry of Food, Agriculture and Fisheries, and the Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (Formas) via the Nordic Joint Committee for Agricultural Research (NKJ). The contribution by Professor Dorthe Wildenschild was funded by the Aarhus University Research Foundation.
Received March 22, 2013.
Accepted for publication July 29, 2013.