Soil pore system evaluated from gas measurements and CT images: A conceptual study using artificial, natural and 3D‐printed soil cores

Abstract

Combining digital imaging, physical models and laboratory measurements is a step further towards a better understanding of the complex relationships between the soil pore system and soil functions. Eight natural 100‐cm3 soil cores were sampled in a cultivated Stagnic Luvisol from the topsoil and subsoil, which we assumed had contrasting pore systems. Artificial 100‐cm3 cores were produced from plastic or from autoclaved aerated concrete (AAC). Eight vertical holes of each diameter (1.5 and 3 mm) were drilled for the plastic cylinder and for one of the two AAC cylinders. All natural and artificial cores were scanned in an X‐ray CT scanner and printed in 3D. Effective air‐filled porosity, true Darcian air permeability, apparent air permeability at a pressure gradient of 5 hPa and oxygen diffusion were measured on all cores. The active pore system characteristics differed between topsoil (sponge‐like, network of macropores of similar size) and subsoil (dominated by large vertical macropores). Active soil pore characteristics measured on a simplified pore network, that is, from artificial and printed soil cores, supported the fundamental differences in air transport by convection and diffusion observed between top‐ and subsoil. The results confirm the suitability of using the conceptual model that partitions the pore system into arterial, marginal and remote pores to describe effects of soil structure on gas transport. This study showed the high potential of using 3D‐printed soil cores to reconstruct the soil macropore network for a better understanding of soil pore functions.

Anisotropy of subsoil pore characteristics and hydraulic conductivity as affected by compaction and cover crop treatments

“…The similar magnitude of anisotropy found among treatments for k a and PO1 indicates that before compaction, airflow mainly happened through vertical pores, which were then reduced in volume after compaction but remained functional for airflow (Schäffer et al., 2008). This finding supports the characterization of agricultural subsoils advanced by the conceptual model of Arah and Ball (1994) and confirmed by Lamandé, Schjønning, Dal Ferro, and Morari (2020), namely that they are dominated by vertical (bio)pores that govern the air transport.…”

Challenges and approaches in assessing the interplay between microorganisms and their physical micro-environments

“…Additive manufacturing is the process of printing successive layers of material on top of each other, although the methods of achieving this vary (see Ngo et al [39] for an overview). Soil structural information acquired by X-ray CT has been subsequently used for printing three-dimensional soil-mimetic structures, in either Nylon 12 or resin with paraffin wax to preserve pore structure [30] , [41] . Hyphal growth of fungi within the pores of the printed structures has also been demonstrated, showing that the structures support microbial growth and exploration [41] .…”

Methods for Studying Bacterial–Fungal Interactions in the Microenvironments of Soil

“…Another interesting method for simulating soil microstructure is 3-D printing. Soil-like structures of nylon 12 or resin with parafilm wax [107,108] can be used to study the exploration and interaction strategies of different microbial inoculates, and may give future insight on BFI in these microhabitats. Some general precautions and limitations should be considered when setting up a microcosm experiment with synthetic soil manufacturing.…”