“…Soils with a large number of disconnected pores are normally characterised by large tortuosity values, which was confirmed by the values for CT (Borges et al, 2018), and likely to have reduced hydraulic conductivity and gaseous diffusion in comparison to soils with higher pore connectivity. Ferreira et al (2018) observed for a Brazilian Dystrudept silty-clay soil that residual pores are characterised by high tortuosity values when compared to connected porous systems, as observed in our work. We found the soil under long-term ZT had lower EPC values, which indicates better pore connectivity.…”
Section: Discussionsupporting
confidence: 87%
“…), Acircular (Ac.) or Acircular-Planar (AP) (Pires et al, 2017; Ferreira et al, 2018). When one of the axes of a specific pore could not be determined by this approach due to their extreme complexity, they were considered non-classified pores (NC).Fig.…”
Zero-tillage (ZT) is being increasingly adopted globally as a conservationist management system due to the environmental and agronomic benefits it provides. However, there remains little information on the tillage effect on soil pore characteristics such as shape, size and distribution, which in turn affect soil physical, chemical and biological processes. X-ray micro Computed Tomography (μCT) facilitates a non-destructive method to assess soil structural properties in three-dimensions. We used X-ray μCT at a resolution of 70 μm to assess and calculate the shape, size and connectivity of the pore network in undisturbed soil samples collected from a long-term experiment (~30 years) under zero tillage (ZT) and conventional tillage (CT) systems in Botucatu, Southeastern Brazil. In both systems, a single, large pore (>1000 mm
3
) typically contributed to a large proportion of macroporosity, 91% in CT and 97% in ZT. Macroporosity was higher in ZT (19.7%) compared to CT (14.3%). However the average number of pores was almost twice in CT than ZT. The largest contribution in both treatments was from very complex shaped pores, followed by triaxial and acircular shaped. Pore connectivity analysis indicated that the soil under ZT was more connected that the soil under CT. Soil under CT had larger values of tortuosity than ZT in line with the connectivity results. The results from this study indicate that long-term adoption of ZT leads to higher macroporosity and connectivity of pores which is likely to have positive implications for nutrient cycling, root growth, soil gas fluxes and water dynamics.
“…Soils with a large number of disconnected pores are normally characterised by large tortuosity values, which was confirmed by the values for CT (Borges et al, 2018), and likely to have reduced hydraulic conductivity and gaseous diffusion in comparison to soils with higher pore connectivity. Ferreira et al (2018) observed for a Brazilian Dystrudept silty-clay soil that residual pores are characterised by high tortuosity values when compared to connected porous systems, as observed in our work. We found the soil under long-term ZT had lower EPC values, which indicates better pore connectivity.…”
Section: Discussionsupporting
confidence: 87%
“…), Acircular (Ac.) or Acircular-Planar (AP) (Pires et al, 2017; Ferreira et al, 2018). When one of the axes of a specific pore could not be determined by this approach due to their extreme complexity, they were considered non-classified pores (NC).Fig.…”
Zero-tillage (ZT) is being increasingly adopted globally as a conservationist management system due to the environmental and agronomic benefits it provides. However, there remains little information on the tillage effect on soil pore characteristics such as shape, size and distribution, which in turn affect soil physical, chemical and biological processes. X-ray micro Computed Tomography (μCT) facilitates a non-destructive method to assess soil structural properties in three-dimensions. We used X-ray μCT at a resolution of 70 μm to assess and calculate the shape, size and connectivity of the pore network in undisturbed soil samples collected from a long-term experiment (~30 years) under zero tillage (ZT) and conventional tillage (CT) systems in Botucatu, Southeastern Brazil. In both systems, a single, large pore (>1000 mm
3
) typically contributed to a large proportion of macroporosity, 91% in CT and 97% in ZT. Macroporosity was higher in ZT (19.7%) compared to CT (14.3%). However the average number of pores was almost twice in CT than ZT. The largest contribution in both treatments was from very complex shaped pores, followed by triaxial and acircular shaped. Pore connectivity analysis indicated that the soil under ZT was more connected that the soil under CT. Soil under CT had larger values of tortuosity than ZT in line with the connectivity results. The results from this study indicate that long-term adoption of ZT leads to higher macroporosity and connectivity of pores which is likely to have positive implications for nutrient cycling, root growth, soil gas fluxes and water dynamics.
“…The visualization, processing and analysis of images were carried out through commercial software AVIZO 9.0 [ 29 ]. The data was denoised with the median filter, which was the frequently adopted approach to process images for noise reducing and edge retaining [ 30 , 31 ].…”
Section: Methodsmentioning
confidence: 99%
“…The soil porosity was determined according to the following equation [ 29 ]: where V p is soil pore volume, whereas V t stands for volume of soil samples. V p and V t can be derived through Volume Fraction of Avizo 9.0.…”
The main forms of poly-γ-glutamic acid (γ-PGA) applied in agriculture include agricultural γ-PGA and γ-PGA super absorbent polymer (SAP). Laboratory experiments were conducted with a check treatment CK (no γ-PGA added) and two different forms of γ-PGA added to sandy loam soil (T and TM stand for γ-PGA and γ-PGA SAP) at four different soil mass ratios (0.05% (1), 0.10% (2), 0.15% (3) and 0.20% (4)) to determine their effects on sandy loam soil hydro-physical properties. Both of them could reduce the cumulative infiltration of soil water. The total available water (TAW) which the soil water content (SWC) from field water capacity (FC) to permanent wilting point (PWP) after γ-PGA added into sandy loam soil had no significant different compared with CK, and the TAW was highest at the treatment of γ-PGA with 0.10% addition amount into sandy loam soil. However, the TAW of sandy loam soil increased dramatically with the γ-PGA SAP addition amount increasing. TM3 had the highest soil water absorption among the treatments with γ-PGA SAP. The T1 to T4 treatments with γ-PGA addition slightly prolonged retention time (RT) when SWC varied from FC to PWP compared with CK. For γ-PGA SAP addition treatments, the time for SWC varied from FC to PWP was 1.48 times (TM1), 1.88 times (TM2), 2.01 times (TM3) and 2.87 times (TM4) longer than that of CK, respectively. The results of this study will provide further information for the use of these materials in agricultural application.
“…The resulting image stack was first processed with the Avizo software to correct for ring artifacts and reduce the noise as well as increase the contrast of the images using smoothing wave and enhancement filtering (cf. Li et al 2017;Ni et al 2017;Ferreira et al 2018). As the olivine is slightly denser than the low-Ca pyroxene, olivine should appear slightly brighter than the pyroxene.…”
Mineralogically zoned chondrules are a common chondrule type in chondrites. They consist of olivine cores, surrounded by low-Ca pyroxene rims. By serial sectioning porphyritic chondrules from carbonaceous, ordinary, and enstatite chondrites, we demonstrate that the 2-D textural appearances of these chondrules largely depend on where they are cut. The same chondrule may appear as a porphyritic pyroxene (PP) chondrule when sectioned through the low-Ca pyroxene rim, and as a porphyritic olivine-pyroxene (POP) or porphyritic olivine (PO) chondrule when sectioned close or through its equator. Chondrules previously classified into PP/POP/PO chondrules might therefore not represent different types, but various sections through mineralogically zoned chondrules. Classifying chondrule textures into PP, POP, and PO has therefore no unequivocal genetic meaning, it is merely descriptive. Sectioning effects further introduce a systematic bias when determining mineralogically zoned chondrule fractions from 2-D sections. We determined correction factors to estimate 3-D mineralogically zoned chondrule fractions when these have been determined in 2-D sections: 1.24 for carbonaceous chondrites, 1.29 for ordinary chondrites, and 1.62 for enstatite chondrites. Using these factors then shows that mineralogically zoned chondrules are the dominant chondrule type in chondrites with estimated 3-D fractions of 92% in CC, 52% in OC, and 46% in EC.
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