X-ray Computed Tomography in Agricultural Systems

A special issue of Agriculture (ISSN 2077-0472). This special issue belongs to the section "Agricultural Technology".

Deadline for manuscript submissions: closed (20 November 2022) | Viewed by 5373

Special Issue Editors

Laboratory of Physics Applied to Soils and Environmental Sciences, Department of Physics, State University of Ponta Grossa, Ponta Grossa 84030-900, Brazil
Interests: X-ray microtomography; nuclear techniques in agriculture; soil pore size distribution; soil physics; water retention curve
Laboratory of Physics Applied to Soils and Environmental Sciences, Department of Physics, State University of Ponta Grossa, Ponta Grossa 84.030-900, Brazil
Interests: X-ray microtomography; soil structure; image analysis; soil pore size distribution; soil pore function; soil physics; water retention

Special Issue Information

Dear Colleagues,

In recent decades, a growing interest in techniques for analyzing the internal structure of soil samples has emerged. Usually, most of the performed studies on soil physics are restricted to analyzing macroscopic soil properties, such as bulk density, porosity, and water retention and infiltration properties. Nonetheless, for understanding or modeling the dynamics of the soil water and the soil aeration, information related to the pore size and shape distributions, pore connectivity, pore tortuosity, pore anisotropy, and pore system complexity are required. In this sense, X-ray microtomography is a technique allowing the study of the soil's inner structure at the micrometric scale. Furthermore, the reconstruction of 3D images permits the simulation of numerous processes inside the soil. Additionally, some CT scanning systems and techniques make it possible to follow physical processes as they happen in the soil (4D tomography). Soil structure modifications due to contrasting tillage systems and uses, continuous wetting and drying cycles, irrigation processes, crop rotation, and compaction are also viable using the microtomographic technique. This Special Issue aims to publish articles related to microtomography in studies involving the investigation of the structure of soils under different agricultural management and when submitted to soil–plant interaction processes.

Prof. Dr. Luiz Fernando Pires
Prof. Dr. Fábio Augusto Meira Cássaro
Guest Editors

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Keywords

  • soil structure
  • soil managements
  • computed tomography
  • image analysis
  • soil pore architecture
  • soil aggregates
  • soil pore functions

Published Papers (3 papers)

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Research

20 pages, 4328 KiB  
Article
Representative Elementary Volume as a Function of Land Uses and Soil Processes Based on 3D Pore System Analysis
by José V. Gaspareto, Jocenei A. T. de Oliveira, Everton Andrade and Luiz F. Pires
Agriculture 2023, 13(3), 736; https://doi.org/10.3390/agriculture13030736 - 22 Mar 2023
Cited by 1 | Viewed by 1569
Abstract
Representative elementary volume (REV) is required for representative measurements of soil physical properties. However, questions may arise whether REV depends on how the soil structure is modified or whether processes in the soil affect REV. Here, we explore REV dependence for contrasting land [...] Read more.
Representative elementary volume (REV) is required for representative measurements of soil physical properties. However, questions may arise whether REV depends on how the soil structure is modified or whether processes in the soil affect REV. Here, we explore REV dependence for contrasting land uses (conventional tillage, no-tillage, and minimum tillage) and applying wetting and drying (W-D) cycles. The effect of different subvolume selection schemes (cube and core) on REV was also investigated. For this study, high-resolution three-dimensional images obtained using the X-ray Computed Tomography (XCT) technique were analyzed. The micromorphological properties measured were porosity (P), fractal dimension (FD), degree of anisotropy (DA), and pore connectivity (C). The results show that REV depends mainly on the land uses for P and C (both selection schemes). The core method showed lower REV due to the larger volume analyzed than that in the cube method. It was not possible to define a REV for DA. The REV obtained using the cube method was more sensitive to changes in the scale of analysis, showing an increasing trend with applied W-D cycles for P and FD. Our results indicate that REV cannot be considered static since land uses and processes influence it. Full article
(This article belongs to the Special Issue X-ray Computed Tomography in Agricultural Systems)
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14 pages, 2253 KiB  
Article
X-ray Microtomography for Investigating Pore Space and Its Relation to Water Retention and Conduction in Highly Weathered Soils
by Thaís Nascimento Pessoa, Talita Rosas Ferreira, Luiz Fernando Pires, Miguel Cooper, Daniel Uteau, Stephan Peth, Carlos Manoel Pedro Vaz and Paulo Leonel Libardi
Agriculture 2023, 13(1), 28; https://doi.org/10.3390/agriculture13010028 - 22 Dec 2022
Cited by 1 | Viewed by 1710
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 [...] Read more.
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 (Ksat); (ii) use µCT to obtain, based on 3D images of soil structure and pore size distribution; and (iii) correlating parameters from SWRCs, Ksat, 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 (ENbigpore): P1 (−44,223 ± 10,096) and P2 (−44,621 ± 12,573) showed more connected pores (ENbigpore) in comparison to P3 (−11,597 ± 6935). The parameter ENbigpore was decisive in understanding the water retention and conduction processes of the studied soils. The better-connected pore space increased Ksat 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. Full article
(This article belongs to the Special Issue X-ray Computed Tomography in Agricultural Systems)
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14 pages, 3810 KiB  
Article
A Comparison of the Differences in Soil Structure under Long-Term Conservation Agriculture Relative to a Secondary Forest
by Luiz F. Pires, Talita R. Ferreira, Fábio A. M. Cássaro, Hannah V. Cooper and Sacha J. Mooney
Agriculture 2022, 12(11), 1783; https://doi.org/10.3390/agriculture12111783 - 27 Oct 2022
Cited by 5 | Viewed by 1355
Abstract
Conservation agriculture is increasingly preferred to conventional methods due to its benefits in promoting more sustainable soil management. Our study aims to compare physical and morphological properties, at the microscale, of soils under long-term no tillage (NT) and minimum-tillage (MT) to adjacent ‘natural’ [...] Read more.
Conservation agriculture is increasingly preferred to conventional methods due to its benefits in promoting more sustainable soil management. Our study aims to compare physical and morphological properties, at the microscale, of soils under long-term no tillage (NT) and minimum-tillage (MT) to adjacent ‘natural’ soils under long-term secondary forest (SF). Soil aggregates of c. 2 cm length were imaged by X-ray Computed Tomography (XCT). The three-dimensional (3D) images were segmented and analyzed in order to assess properties such as porosity, number of pores, degree of anisotropy, pore shape, volume classifications, Euler number for pore connectivity, and pore tortuosity. The pore architecture of soils under NT and MT, for c. 40 years, was similar to that from the SF in terms of imaged porosity, pore size, and shape distributions, as hypothesized in our study. However, we observed some important differences; for instance, SF had larger, more connected, and more complex pores, likely due to the greater biological activity. In addition, SF had more isotropic pores than NT and MT, i.e., without preferential flow paths for water redistribution. Therefore, we concluded that long-term conservation agriculture was efficient at reversing structural damage typically associated with conventional, intensive agriculture, but some large differences remain, particularly concerning the pore network complexity and connectivity. Full article
(This article belongs to the Special Issue X-ray Computed Tomography in Agricultural Systems)
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