scholarly journals Effect of long-term irrigation and tillage practices on X-ray CT and gas transport derived pore-network characteristics

Soil Research ◽  
2019 ◽  
Vol 57 (6) ◽  
pp. 657
Author(s):  
Karin Müller ◽  
Nicola Dal Ferro ◽  
Sheela Katuwal ◽  
Craig Tregurtha ◽  
Filippo Zanini ◽  
...  
Keyword(s):  
Gas Transport ◽  
Greenhouse Gas Emission ◽  
Structural Characteristics ◽  
Network Connectivity ◽  
Total Porosity ◽  
Pore Network ◽  
Transport Parameters ◽  
X Ray ◽  
Tillage Practices

The gas transport parameters, diffusivity and air-filled porosity are crucial for soil aeration, microbial activity and greenhouse gas emission, and directly depend on soil structure. In this study, we analysed the effect of long-term tillage and irrigation practices on the surface structure of an arable soil in New Zealand. Our hypothesis was that topsoil structure would change under intensification of arable production, affecting gas exchange. Intact soil cores were collected from plots under intensive tillage (IT) and direct drill (DD), irrigated or rainfed. In total, 32 cores were scanned by X-ray computed tomography (CT) to derive the pore network >30µm. The cores were then used to measure soil-gas diffusivity, air-permeability and air-filled porosity of pores close to the resolution of the X-ray CT scans, namely ≥30µm. The gas measurements allow the calculation of pore-network connectivity and tortuosity parameters, which were compared with the CT-derived structural characteristics. Long-term irrigation had little effect on any of the parameters analysed. Total porosity tended to be lower under IT than DD, whereas the CT-derived porosity was comparable. Both the CT-derived mean pore diameter (MPD) and other morphological parameters, as well as gas measurement-derived parameters, highlighted a less developed structure under IT. The differences in the functional pore-network structure were attributed to SOC depletion and the mechanical disturbance through IT. Significant correlations between CT-derived parameters and functional gas transport parameters such as tortuosity and MPD were found, which suggest that X-ray CT could be useful in the prediction of gas transport.

Linking pore network structure derived by microfocus X-ray CT to mass transport parameters in differently compacted loamy soils

Soil Research ◽  
2019 ◽  
Vol 57 (6) ◽  
pp. 642
Author(s):  
Arjun Baniya ◽  
Ken Kawamoto ◽  
Shoichiro Hamamoto ◽  
Toshihiro Sakaki ◽  
Takeshi Saito ◽  
...  
Keyword(s):  
Mass Transport ◽  
Coordination Number ◽  
Structural Parameters ◽  
Network Connectivity ◽  
Pore Network ◽  
Gas Diffusion ◽  
Transport Parameters ◽  
X Ray ◽  
Surface Areas ◽  
X Ray Computed

Mass transport in soil occurs through the soil pore network, which is highly influenced by pore structural parameters such as pore-size distribution, porosity, pore tortuosity, and coordination number. In this study, we visualised the networks of meso- and macro-pores (typical pore radius r ≥ 10 μm) using microfocus X-ray computed tomography (MFXCT) and evaluated pore structural parameters of two loamy soils from Japan and New Zealand packed at different degrees of compaction. The effect of compaction on pore structural parameters and relationships between pore structural parameters and measured mass transport parameters were examined. Results showed a clear influence of compaction on pore structural parameters, with the MFXCT-derived mean pore radii and pore tortuosities decreasing and the mean pore coordination number increasing with increasing dry bulk density. Especially, pores with r > 80 µm became finer or were not well formed due to compaction. The MFXCT-derived pore structural parameters were not well correlated with the equivalent pore radii from measured water retention curves. However, volumetric surface areas and pore-network connectivity-tortuosity factors derived from MFXCT allowed a fair prediction of several important mass transport parameters such as saturated hydraulic conductivities, soil-gas diffusion coefficients, and soil-air permeabilities. Further studies are needed to link micro-pores with radii smaller than the X-ray CT resolution to meso- and macro-pores visualised by X-ray CT to improve the prediction of mass transport parameters in soil.

Comparison of soil CO2 emissions from three different tillage methods on chernozem soil

2021 ◽  
Author(s):  
Márton Dencső ◽  
Ágota Horel ◽  
Zsófia Bakacsi ◽  
Eszter Tóth
Keyword(s):  
Greenhouse Gas Emission ◽  
Environmental Parameters ◽  
Conventional Tillage ◽  
No Tillage ◽  
Chernozem Soil ◽  
Long Term Effects ◽  
Tillage Practices ◽  
The Difference ◽  
Tillage Methods

<p>Tillage practices influence soil CO<sub>2</sub> emissions, hence many research investigate the long-term effects of conservation and conventional tillage methods e.g. ploughing and no-tillage on soil greenhouse gas emission.</p><p>The experiment site is an 18-years-old long-term tillage trial established on chernozem soil. During 2020, we took weekly CO<sub>2 </sub>emission measurements in the mouldboard ploughing (MP), no-tillage (NT), and shallow cultivation (SC) treatments Tillage depth was 26-30 cm, 12-16 cm and 0 cm in the cases of MP, SC and NT respectively. The experiment was under wither oat cultivation.</p><p>We investigated the similarity in the CO<sub>2</sub> emission trends of SC to MP or NT treatments. Besides CO<sub>2</sub> emission measurements, we also monitored environmental parameters such as soil temperature (Ts) and soil water content (SWC) in each treatment.</p><p>During the investigated year (2020 January - December) SC had higher annual mean CO<sub>2</sub> emission (0.115±0.083 mg m<sup>-2</sup> s<sup>-1</sup>) compared to MP (0.099±0.089 mg m<sup>-2</sup> s<sup>-1</sup>) and lower compared to NT (0.119±0.100 mg m<sup>-2</sup> s<sup>-1</sup>). The difference of the CO<sub>2</sub> emissions was significant between SC and MP (p<0.05); however, it was not significant between SC and NT (p>0.05) treatments. The Ts dependency of CO<sub>2</sub> emission was moderate in all treatments. CO<sub>2</sub> emissions were moderately depended on SWC in MP and SC, and there was no correlation between these parameters in NT.</p><p>The annual mean CO<sub>2</sub> emission of the SC treatment was more similar to the NT, than to the MP treatment.</p>

scholarly journals Pore network structure linked by X-ray CT to particle characteristics and transport parameters

2016 ◽  
Vol 56 (4) ◽  
pp. 676-690 ◽  
Author(s):  
Shoichiro Hamamoto ◽  
Per Moldrup ◽  
Ken Kawamoto ◽  
Toshihiro Sakaki ◽  
Taku Nishimura ◽  
...  
Keyword(s):  
Network Structure ◽  
Pore Network ◽  
Transport Parameters ◽  
X Ray ◽  
Particle Characteristics

scholarly journals Pore morphology of polar firn around closure revealed by X-ray tomography

2018 ◽  
Author(s):  
Alexis Burr ◽  
Clément Ballot ◽  
Pierre Lhuissier ◽  
Patricia Martinerie ◽  
Christophe L. Martin ◽  
...  
Keyword(s):  
Sample Size ◽  
Morphological Evolution ◽  
Total Porosity ◽  
Pore Network ◽  
Geometrical Parameters ◽  
Age Difference ◽  
X Ray ◽  
Porosity Ratio ◽  
Pore Closure ◽  
Lock In

Abstract. Understanding the slow densification process of polar firn into ice is essential in order to constrain the age difference between the ice matrix and entrapped gases. The progressive microstructure evolution of the firn column with depth leads to pore closure and gas entrapment. Air transport models in the firn usually include a closed porosity profile based on available data. Pycnometry or melting-refreezing techniques have been used to obtain the ratio of closed to total porosity and air content in closed pores, respectively. X-ray computed tomography is complementary to these methods, as it enables to obtain the full pore network in 3D. This study takes advantage of this non-destructive technique to discuss the morphological evolution of pores on four different Antarctic sites. The computation of refined geometrical parameters for the very cold polar sites Dome C and Lock In (the two Antarctic plateau sites studied here) provides new information that could be used in further studies. The comparison of these two sites shows a more tortuous pore network at Lock In than at Dome C which should result in older gas ages in deep firn. A comprehensive estimation of the different errors related to X-ray tomography and to the sample variability has been performed. The procedure described here may be used as a guideline for further experimental characterization on firn samples. We show that the closed to total porosity ratio, which is classically used for the detection of pore closure, is strongly affected by the sample size, the image reconstruction and by spatial heterogeneities. In this work, we introduce an alternative parameter, the connectivity index, which is practically independent on sample size and image acquisition conditions, and that accurately predicts the close-off depth and density. Its strength also lies in its simple computation, without any assumption on the pore status (open or close). The close-off prediction is obtained for Dome C and Lock In, without any further numerical simulations on images (e.g. by permeability or diffusivity calculations).

Investigating hydrogel potentialities for improving soil pore network by using X-ray computed microtomography

2020 ◽  
Author(s):  
Ilaria Piccoli ◽  
Pozza Sara ◽  
Carlo Camarotto ◽  
Andrea Squartini ◽  
Giacomo Guerrini ◽  
...  
Keyword(s):  
Water Saturation ◽  
Food Additives ◽  
Total Porosity ◽  
Pore Network ◽  
Future Research ◽  
High Water Content ◽  
Swelling Properties ◽  
X Ray ◽  
Computed Microtomography ◽  
X Ray Computed

<p>Hydrogels (HGs) are conventionally defined as a natural or synthetic polymeric 3D networks with high hygroscopicity and water-swelling properties. Over the decades, HGs have been widely utilized in various fields of cosmetics, food additives, tissue engineering, drug delivery, and pharmaceuticals. Only recently HGs have been studied also for agronomic purpose. Indeed, their unique physical properties, including their porosity and swellability, make them ideal platforms for water and nutrient delivering. The aim of this study was to investigate the potentialities of two HGs, one formed by polyacrylamide and one by cellulose added with clay and humic acids, for improving soil porosity of three soil types (sandy “SD”, silty “SL” and clay “CL”). Soil pore network was characterized with X-ray computed microtomography (µCT) at 50 µm resolution and subsequent image analysis measuring  total porosity (TP), pore size distribution (PSD), mean diameter (MD), connectivity density and degree of anisotropy. Soil samples were at first saturated and then dried trough freezing and drying cycles with acetone at -80°c.</p><p>Preliminary results showed that at water saturation HG increased TP of four- and two-fold, respectively for SL and CL soil, MD of 40 (SD), 519 (SL) and 164 µm (CL) while no effects were found on other pore architecture indices (e.g., connectivity or anisotropy). The PSD analysis highlighted that HG increased the macroporosity fraction (e.g., pore > 0.8 mm) only in SL (+36%) and CL (+11%) while the other pore classes were not affected. Present study demonstrated that in fine-textured soils at high water content, HG might be a valuable tool to increase not simply the TP but, in particular, the macroporosity fraction which may play a key role in soil functioning and ecosystem services. Future research will investigate the HG performances under dynamic soil moisture conditions on water holding capacity and hydraulic conductivity (Research supported by Fondazione CARIPARO, InnoGel, Progetti Eccellenza 2017).</p>

scholarly journals An intercomparison of the pore network to the Navier–Stokes modeling approach applied for saturated conductivity estimation from X-ray CT images

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Bartłomiej Gackiewicz ◽  
Krzysztof Lamorski ◽  
Cezary Sławiński ◽  
Shao-Yiu Hsu ◽  
Liang-Cheng Chang
Keyword(s):  
Porous Media ◽  
Specific Surface ◽  
Total Porosity ◽  
Pore Network ◽  
Ct Images ◽  
Navier Stokes ◽  
X Ray ◽  
Average Value ◽  
Modeling Approaches ◽  
The Difference

AbstractDifferent modeling techniques can be used to estimate the saturated conductivity of a porous medium based on computed tomography (CT) images. In this research, two methods are intercompared: direct modeling using the Navier–Stokes (NS) approach and simplified geometry pore network (PN) modeling. Both modeling approaches rely on pore media geometry which was determined using an X-ray CT scans with voxel size 2 μm. An estimate of the saturated conductivity using both methods was calculated for 20 samples prepared from sand with diverse particle size distributions. PN-estimated saturated conductivity was found to be statistically equivalent to the NS-determined saturated conductivity values. The average value of the ratio of the PN-determined conductivity to the NS-determined conductivity (KsatPN/NS) was equal to 0.927. In addition to the NS and PN modeling approaches, a simple Kozeny-Carman (KC) equation-based estimate was made. The comparison showed that the KC estimate overestimated saturated conductivity by more than double (2.624) the NS estimate. A relationship was observed between the porous media specific surface and the KsatPN/NS ratio. The tortuosity of analyzed samples was estimated, the correlation between the porous media tortuosity and the specific surface of the samples was observed. In case of NS modelling approach the difference between pore media total porosity and total porosity of meshes, which were lower, generated for simulations were observed. The average value of the differences between them was 0.01. The method of NS saturated conductivity error estimation related to pore media porosity underestimation by numerical meshes was proposed. The error was on the average 10% for analyzed samples. The minimum value of the error was 4.6% and maximum 19%.

Two decades of no-till in the Oberacker long-term field experiment: Part II. Soil porosity and gas transport parameters

2016 ◽  
Vol 163 ◽  
pp. 130-140 ◽  
Author(s):  
Ingrid Martínez ◽  
Andreas Chervet ◽  
Peter Weisskopf ◽  
Wolfgang G. Sturny ◽  
Jan Rek ◽  
...  
Keyword(s):  
Field Experiment ◽  
Gas Transport ◽  
Soil Porosity ◽  
Transport Parameters ◽  
No Till ◽  
Term Field

scholarly journals X-ray micro-computed tomography characterized soil pore network as influenced by long-term application of manure and fertilizer

Geoderma ◽  
2021 ◽  
Vol 385 ◽  
pp. 114872
Author(s):  
Navdeep Singh ◽  
Sandeep Kumar ◽  
Ranjith P. Udawatta ◽  
Stephen H. Anderson ◽  
Lis W. de Jonge ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Pore Network ◽  
Micro Computed Tomography ◽  
X Ray

Correlating Gas Transport Parameters and X-Ray Computed Tomography Measurements in Porous Media

Soil Science ◽  
2013 ◽  
Vol 178 (2) ◽  
pp. 60-68 ◽  
Author(s):  
Muhammad Naveed ◽  
Shoichiro Hamamoto ◽  
Ken Kawamoto ◽  
Toshihiro Sakaki ◽  
Manabu Takahashi ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Porous Media ◽  
Gas Transport ◽  
Transport Parameters ◽  
X Ray ◽  
X Ray Computed

scholarly journals Macro- and microscale gaseous diffusion in a Stagnic Luvisol as affected by compaction and reduced tillage

2008 ◽  
Vol 17 (3) ◽  
pp. 252 ◽  
Author(s):  
A. SIMOJOKI ◽  
O. FAZEKAS-BECKER ◽  
R. HORN
Keyword(s):  
Soil Compaction ◽  
Soil Structure ◽  
Gas Transport ◽  
Near Field ◽  
Field Capacity ◽  
Conventional Tillage ◽  
Reduced Tillage ◽  
Tillage Practices ◽  
Conservation Treatment

Intensification of mechanical agriculture has increased the risk for soil compaction and deformation. Simultaneously, reduced tillage practices have become popular due to energy saving and environmental concerns, as they may strengthen and improve the functioning of structured soil pore system. Soil aeration is affected by both compaction and reduced tillage through changes in soil structure and in the distribution of easily decomposable organic matter. We investigated whether a single wheeling by a 35 000 kg sugar-beet harvester in a Stagnic Luvisol derived from loess near Göttingen, Germany, influenced the gas transport properties (air permeability, gaseous macro- and microdiffusivities, oxygen diffusion rate) in the topsoil and subsoil samples, and whether the effects were different between long-term reduced tillage and mouldboard ploughing. Poor structure in the topsoil resulted in slow macro- and microscale gas transport at moisture contents near field capacity. The macrodiffusivities in the topsoil under conventional tillage were slower compared with those under conservation treatment, and soil compaction reduced the diffusivities by about half at the soil depths studied. This shows that even one pass with heavy machinery near field capacity impairs soil structure deep into the profile, and supports the view that reduced tillage improves soil structure and aeration compared with ploughing, especially in the topsoil.;

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