X-ray Microtomography for Investigating Pore Space and Its Relation to Water Retention and Conduction in Highly Weathered Soils

Thaís Nascimento Pessoa (), Talita Rosas Ferreira, Luiz Fernando Pires, Miguel Cooper, Daniel Uteau, Stephan Peth, Carlos Manoel Pedro Vaz and Paulo Leonel Libardi
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Thaís Nascimento Pessoa: Department of Soil Science, University of São Paulo-“Luiz de Queiroz” College of Agriculture, Pádua Dias Avenue, 11, Piracicaba 13418-900, Brazil
Talita Rosas Ferreira: Brazilian Synchrotron Light Laboratory (LNLS), Brazilian Center for Research in Energy and Materials (CNPEM), Campinas 13083-970, Brazil
Luiz Fernando Pires: Laboratory of Physics Applied to Soils and Environmental Sciences, State University of Ponta Grossa, Ponta Grossa 84030-900, Brazil
Miguel Cooper: Department of Soil Science, University of São Paulo-“Luiz de Queiroz” College of Agriculture, Pádua Dias Avenue, 11, Piracicaba 13418-900, Brazil
Daniel Uteau: Department of Soil Science, Faculty of Ecological Agriculture, University of Kassel, 37213 Witzenhausen, Germany
Stephan Peth: Institute of Soil Science, Leibniz Universität Hannover, 30419 Hannover, Germany
Carlos Manoel Pedro Vaz: Embrapa Agricultural Instrumentation, São Carlos 13560-970, Brazil
Paulo Leonel Libardi: Department of Soil Science, University of São Paulo-“Luiz de Queiroz” College of Agriculture, Pádua Dias Avenue, 11, Piracicaba 13418-900, Brazil

Agriculture, 2022, vol. 13, issue 1, 1-14

Abstract: Soil structure controls soil hydraulic properties and is linked to soil aggregation processes. The aggregation processes of Oxisols are controlled mainly by clay mineralogy and biological activity. Computed microtomography (µCT) may be a tool for improving the knowledge of the hydraulic properties of these soils. Thus, this study brings an advance in the use of 3D image analysis to better comprehend the water behavior in tropical soils. In this work, three Oxisols were studied with the objective to (i) characterize the soil water retention curve (SWRC), the corresponding pore size frequency, and the saturated hydraulic conductivity (K sat ); (ii) use µCT to obtain, based on 3D images of soil structure and pore size distribution; and (iii) correlating parameters from SWRCs, K sat , and µCT with other physical-hydric, chemical, and mineralogical attributes. Rhodic Haplustox—P1, Anionic Acrustox—P2, and Typic Hapludox—P3 were the three studied Oxisols. The differences among the SWRCs were related to the microgranular and block type’s structure morphology, which modified the soil pore space. The pore size frequency was calculated from SWRCs for pores with diameters of 87 ± 2 μm in P1, 134 ± 11μm in P2, and 175 ± 18 μm in P3. Pore size distribution from µCT was determined for the range of 20–100 µm, mainly with the highest percentages: 12 ± 1.09% for P1 and 12 ± 1.4% for P2. Pore connectivity was assessed from images by calculating Euler Numbers (EN), with the differences related to the biggest pore (EN bigpore ): P1 (−44,223 ± 10,096) and P2 (−44,621 ± 12,573) showed more connected pores (EN bigpore ) in comparison to P3 (−11,597 ± 6935). The parameter EN bigpore was decisive in understanding the water retention and conduction processes of the studied soils. The better-connected pore space increased K sat in P1 (220 ± 0.05 mm h −1 ) and P2 (189 ± 0.1 mm h −1 ) in comparison to P3 (20 ± 0.3 mm h −1 ) and modified the shape of SWRCs.

Keywords: soil water retention curve; pore size distribution; pore connectivity; iron and aluminum oxides; microaggregates (search for similar items in EconPapers)
JEL-codes: Q1 Q10 Q11 Q12 Q13 Q14 Q15 Q16 Q17 Q18 (search for similar items in EconPapers)
Date: 2022
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