3D‐visualization and analysis of macro‐ and meso‐porosity of the upper horizons of a sodic, texture‐contrast soil

Abstract

SummaryThe lower E and upper B horizons of sodic, texture-contrast soils are a formidable barrier to most annual and many perennial crops. The research presented here is part of a wider study into the nature of subsoil constraints to root exploration. The aim of this study was to characterize in three dimensions the macroand meso-porosity across the E horizon-Btn horizon interface of a sodic, texture-contrast soil using X-ray computed tomography (CT). Intact soil cores of 50-cm length and 15-cm diameter were scanned with a medical CT X-ray machine. The pore volume reconstructed from these scans had a resolution of 0.3 Â 0.3 Â 0.4 cm (in the x, y, z dimensions, respectively). This resolution allowed visualization and quantification of the macroporosity of the intact cores. Undisturbed samples of 1.5-cm diameter and 4-cm length were carefully excised from the interface and scanned with micro-CT X-ray equipment. The reconstructed pore volumes had an isotropic resolution of 19 mm that allowed analysis of the mesoporosity just on the boundary between the E and Btn horizons. Mesoporosity decreased across the interface and increased lower in the Btn horizon. The distribution of the pores at the macro-and meso-scales showed the importance of the smaller pores in the A and E horizons, whereas most of the porosity in the Btn horizon was attributed to the larger pores. Pores in this sodic, texture-contrast soil were not distributed homogeneously at either the macro-or meso-scale. A greater proportion of the pores in the E-B interface were horizontal than in the upper A1, upper E and lower Btn horizons. Some 'coiling' of the pores was also apparent in the interface. The shape of some pores (long tubular pores) suggested formation by roots as they drilled through the soil. The orientation of these pores was a function of physical (and possibly chemical) impedance at the interface.

Quantitative evaluation of pore characteristics of sodic soils reclaimed by flue gas desulphurization gypsum using X‐ray computed tomography

“…Therefore, the lower pore length density was considered to be another feature of sodic soil. The tortuosity measured in this study was smaller than those of 1.5–2.5 reported by Jassogne et al (), 1.34–1.70 by Luo, Lin, and Li (), and 1.96–2.05 by Zhou et al () but larger than those of 1.12–1.17 by Perret, Prasher, Kantzas, and Langford () and 1.25 by Katuwal et al (). Zhou et al () attributed the higher tortuosity to the complex aggregates and its irregular spatial structure.…”

“…The results showed that the proportion of vertical porosity was mostly smaller (p < .05) than that of horizontal porosity for all pores (Table 2), and the proportion of horizontal porosity of the three types of sodic soils were obviously higher than those of cultivated soils reported by previous studies (Jassogne et al, 2007;Katuwal et al, 2015;Luo, Lin, & Li, 2010), indicating that high proportion of horizontal pores was the most typical feature of the pore structure of the investigated sodic soils.…”

Quantitative evaluation of pore characteristics of sodic soils reclaimed by flue gas desulphurization gypsum using X‐ray computed tomography

“…Therefore, the lower pore length density was considered to be another feature of sodic soil. The tortuosity measured in this study was smaller than those of 1.5–2.5 reported by Jassogne et al (), 1.34–1.70 by Luo, Lin, and Li (), and 1.96–2.05 by Zhou et al () but larger than those of 1.12–1.17 by Perret, Prasher, Kantzas, and Langford () and 1.25 by Katuwal et al (). Zhou et al () attributed the higher tortuosity to the complex aggregates and its irregular spatial structure.…”

“…The results showed that the proportion of vertical porosity was mostly smaller (p < .05) than that of horizontal porosity for all pores (Table 2), and the proportion of horizontal porosity of the three types of sodic soils were obviously higher than those of cultivated soils reported by previous studies (Jassogne et al, 2007;Katuwal et al, 2015;Luo, Lin, & Li, 2010), indicating that high proportion of horizontal pores was the most typical feature of the pore structure of the investigated sodic soils.…”

Influence of Root Distribution on Preferential Flow in Deciduous and Coniferous Forest Soils

“…Additionally, organic remains of root material and active microbial populations can improve the circumstances for macropores. These channels can also provide paths for new fine root growth with small mechanical resistance and high availability of water, air, and nutrients [21,78]. In our study, coarse roots seem to play a small role (less than 10% of total root occurrence for the entire soil profile; Figure 4).…”

X-ray computed microtomography in the evaluation of the porous system of soils

“…Pore inclination and tortuosity represent the need for root branching in the search for nutrients and water. In addition, pore inclination is strongly related to water infiltration in the soil; horizontal pores, especially on soil surface, lead to a significant reduction in water infiltration (Jassogne et al, 2007).…”

Quantitative evaluation of pore characteristics of sodic soils reclaimed by flue gas desulphurization gypsum using X‐ray computed tomography

“…Therefore, the lower pore length density was considered to be another feature of sodic soil. The tortuosity measured in this study was smaller than those of 1.5–2.5 reported by Jassogne et al (), 1.34–1.70 by Luo, Lin, and Li (), and 1.96–2.05 by Zhou et al () but larger than those of 1.12–1.17 by Perret, Prasher, Kantzas, and Langford () and 1.25 by Katuwal et al (). Zhou et al () attributed the higher tortuosity to the complex aggregates and its irregular spatial structure.…”

“…The results showed that the proportion of vertical porosity was mostly smaller (p < .05) than that of horizontal porosity for all pores (Table 2), and the proportion of horizontal porosity of the three types of sodic soils were obviously higher than those of cultivated soils reported by previous studies (Jassogne et al, 2007;Katuwal et al, 2015;Luo, Lin, & Li, 2010), indicating that high proportion of horizontal pores was the most typical feature of the pore structure of the investigated sodic soils.…”

Influence of Root Distribution on Preferential Flow in Deciduous and Coniferous Forest Soils

“…Additionally, organic remains of root material and active microbial populations can improve the circumstances for macropores. These channels can also provide paths for new fine root growth with small mechanical resistance and high availability of water, air, and nutrients [21,78]. In our study, coarse roots seem to play a small role (less than 10% of total root occurrence for the entire soil profile; Figure 4).…”

X-ray computed microtomography in the evaluation of the porous system of soils

“…Pore inclination and tortuosity represent the need for root branching in the search for nutrients and water. In addition, pore inclination is strongly related to water infiltration in the soil; horizontal pores, especially on soil surface, lead to a significant reduction in water infiltration (Jassogne et al, 2007).…”

Quantitative evaluation of pore characteristics of sodic soils reclaimed by flue gas desulphurization gypsum using X‐ray computed tomography

“…Therefore, the lower pore length density was considered to be another feature of sodic soil. The tortuosity measured in this study was smaller than those of 1.5–2.5 reported by Jassogne et al (), 1.34–1.70 by Luo, Lin, and Li (), and 1.96–2.05 by Zhou et al () but larger than those of 1.12–1.17 by Perret, Prasher, Kantzas, and Langford () and 1.25 by Katuwal et al (). Zhou et al () attributed the higher tortuosity to the complex aggregates and its irregular spatial structure.…”

“…The results showed that the proportion of vertical porosity was mostly smaller (p < .05) than that of horizontal porosity for all pores (Table 2), and the proportion of horizontal porosity of the three types of sodic soils were obviously higher than those of cultivated soils reported by previous studies (Jassogne et al, 2007;Katuwal et al, 2015;Luo, Lin, & Li, 2010), indicating that high proportion of horizontal pores was the most typical feature of the pore structure of the investigated sodic soils.…”

Influence of Root Distribution on Preferential Flow in Deciduous and Coniferous Forest Soils

“…Additionally, organic remains of root material and active microbial populations can improve the circumstances for macropores. These channels can also provide paths for new fine root growth with small mechanical resistance and high availability of water, air, and nutrients [21,78]. In our study, coarse roots seem to play a small role (less than 10% of total root occurrence for the entire soil profile; Figure 4).…”

X-ray computed microtomography in the evaluation of the porous system of soils

“…Pore inclination and tortuosity represent the need for root branching in the search for nutrients and water. In addition, pore inclination is strongly related to water infiltration in the soil; horizontal pores, especially on soil surface, lead to a significant reduction in water infiltration (Jassogne et al, 2007).…”