Forests · 2026
Soil Pore Architecture and Hydraulic Functioning of Native Forest and Sugarcane Systems with and Without Cover Crop Intercropping Revealed by X-Ray Computed Tomography
Awe, G. O., de Oliveira Ferreira, A., de Almeida, B. G., da Silva, W. R., Antonino, A. C. D., Reichert, J. M.
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Soil Pore Architecture and Hydraulic Functioning of Native F…
Abstract
Soil pore architecture and hydraulic functioning strongly regulate water flow and retention. However, despite the growing application of X-ray computed tomography (X-ray CT) in soil science, its application in characterizing the pore system and hydraulic functioning of native forest soils converted to sugarcane production systems in northeast Brazil is still poorly known. This study therefore quantified the soil structure, pore system, and hydraulic functioning of a native forest (NF) and an adjacent sugarcane field receiving vinasse and managed without intercropping (sole sugarcane (SG)) and with Brachiaria ruziziensis intercropping (SG + Bra intercrop) in northeastern Brazil, using conventional soil physical measurements and X-ray CT, in three soil layers (0–10, 10–20, and 20–40 cm). Soil physical and hydraulic properties, as well as soil water retention, were quantified. The native forest soil exhibited a uniformly sandy texture across all depths, whereas sugarcane systems ranged from loam to sandy textures in surface layers due to long-term management. Soil organic matter and total nitrogen in the 0–10 cm layer were approximately 75 and 65% higher, respectively, in sole Sole SG and SG + Bra intercrop than in NF. Soil bulk density increased with depth under sugarcane, reaching values about 10%–13% higher than NF in the 20–40 cm layer. Saturated hydraulic conductivity in the surface layer was higher in the NF, approximately five to nine times greater than in sole SG and SG + Bra intercrop, respectively. Conventional water retention analysis showed that sole SG and SG + Bra intercrop had greater total porosity (0.49–0.55 m3 m−3), microporosity (0.26–0.36 m3 m−3), field capacity (0.19–0.33 m3 m−3), and plant available water (0.09–0.15 m3 m−3) in the upper 20 cm compared with the NF (≤0.10 m3 m−3 available water). In contrast, X-ray CT revealed higher macroporosity (0.20–0.23 mm3 mm−3) and pore connectivity in the NF across all depths, with predominantly complex, inclined to near-horizontal pores and low anisotropy. Intercropping sugarcane with Brachiaria did not significantly alter (p > 0.05) bulk density, hydraulic conductivity, or CT-derived pore connectivity relative to sole sugarcane. The degree of anisotropy and fractal dimension derived from X-ray CT were significantly correlated (p < 0.05) with conventionally measured hydraulic properties. The X-ray computed tomography proved effective in linking pore-scale architecture to soil hydraulic functioning, providing insights beyond conventional measurements. The short-term inclusion of Brachiaria as a cover crop at 10 kg seed ha−1 did not result in significant improvements in soil pore structure, indicating that longer-term adoption and/or higher planting densities may be required to induce measurable changes in pore system architecture and soil hydraulic functioning.
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Soil pore architecture and hydraulic functioning strongly regulate water flow and retention. However, despite the growing application of X-ray computed tomography (X-ray CT) in soil science, its application in characterizing the pore system and hydraulic functioning of native forest soils converted to sugarcane production systems in northeast Brazil is still poorly known. This study therefore quantified the soil structure, pore system, and hydraulic functioning of a native forest (NF) and an adjacent sugarcane field receiving vinasse and managed without intercropping (sole sugarcane (SG)) and with Brachiaria ruziziensis intercropping (SG + Bra intercrop) in northeastern Brazil, using conventional soil physical measurements and X-ray CT, in three soil layers (0–10, 10–20, and 20–40 cm). Soil physical and hydraulic properties, as well as soil water retention, were quantified. The native forest soil exhibited a uniformly sandy texture across all depths, whereas sugarcane systems ranged from loam to sandy textures in surface layers due to long-term management. Soil organic matter and total nitrogen in the 0–10 cm layer were approximately 75 and 65% higher, respectively, in sole Sole SG and SG + Bra intercrop than in NF. Soil bulk density increased with depth under sugarcane, reaching values about 10%–13% higher than NF in the 20–40 cm layer. Saturated hydraulic conductivity in the surface layer was higher in the NF, approximately five to nine times greater than in sole SG and SG + Bra intercrop, respectively. Conventional water retention analysis showed that sole SG and SG + Bra intercrop had greater total porosity (0.49–0.55 m3 m−3), microporosity (0.26–0.36 m3 m−3), field capacity (0.19–0.33 m3 m−3), and plant available water (0.09–0.15 m3 m−3) in the upper 20 cm compared with the NF (≤0.10 m3 m−3 available water). In contrast, X-ray CT revealed higher macroporosity (0.20–0.23 mm3 mm−3) and pore connectivity in the NF across all depths, with predominantly complex, inclined to near-horizontal pores and low anisotropy. Intercropping sugarcane with Brachiaria did not significantly alter (p > 0.05) bulk density, hydraulic conductivity, or CT-derived pore connectivity relative to sole sugarcane. The degree of anisotropy and fractal dimension derived from X-ray CT were significantly correlated (p < 0.05) with conventionally measured hydraulic properties. The X-ray computed tomography proved effective in linking pore-scale architecture to soil hydraulic functioning, providing insights beyond conventional measurements. The short-term inclusion of Brachiaria as a cover crop at 10 kg seed ha−1 did not result in significant improvements in soil pore structure, indicating that longer-term adoption and/or higher planting densities may be required to induce measurable changes in pore system architecture and soil hydraulic functioning.
Soil pore architecture and hydraulic functioning strongly regulate water flow and retention. However, despite the growing application of X-ray computed tomography (X-ray CT) in soil science, its application in characterizing the pore system and hydraulic functioning of native forest soils converted to sugarcane production systems in northeast Brazil is still poorly known. This study therefore quantified the soil structure, pore system, and hydraulic functioning of a native forest (NF) and an adjacent sugarcane field receiving vinasse and managed without intercropping (sole sugarcane (SG)) and with Brachiaria ruziziensis intercropping (SG + Bra intercrop) in northeastern Brazil, using conventional soil physical measurements and X-ray CT, in three soil layers (0–10, 10–20, and 20–40 cm). Soil physical and hydraulic properties, as well as soil water retention, were quantified. The native forest soil exhibited a uniformly sandy texture across all depths, whereas sugarcane systems ranged from loam to sandy textures in surface layers due to long-term management. Soil organic matter and total nitrogen in the 0–10 cm layer were approximately 75 and 65% higher, respectively, in sole Sole SG and SG + Bra intercrop than in NF. Soil bulk density increased with depth under sugarcane, reaching values about 10%–13% higher than NF in the 20–40 cm layer. Saturated hydraulic conductivity in the surface layer was higher in the NF, approximately five to nine times greater than in sole SG and SG + Bra intercrop, respectively. Conventional water retention analysis showed that sole SG and SG + Bra intercrop had greater total porosity (0.49–0.55 m3 m−3), microporosity (0.26–0.36 m3 m−3), field capacity (0.19–0.33 m3 m−3), and plant available water (0.09–0.15 m3 m−3) in the upper 20 cm compared with the NF (≤0.10 m3 m−3 available water). In contrast, X-ray CT revealed higher macroporosity (0.20–0.23 mm3 mm−3) and pore connectivity in the NF across all depths, with predominantly complex, inclined to near-horizontal pores and low anisotropy. Intercropping sugarcane with Brachiaria did not significantly alter (p > 0.05) bulk density, hydraulic conductivity, or CT-derived pore connectivity relative to sole sugarcane. The degree of anisotropy and fractal dimension derived from X-ray CT were significantly correlated (p < 0.05) with conventionally measured hydraulic properties. The X-ray computed tomography proved effective in linking pore-scale architecture to soil hydraulic functioning, providing insights beyond conventional measurements. The short-term inclusion of Brachiaria as a cover crop at 10 kg seed ha−1 did not result in significant improvements in soil pore structure, indicating that longer-term adoption and/or higher planting densities may be required to induce measurable changes in pore system architecture and soil hydraulic functioning.
Findings
What changed what, as the paper reports it. Grouped by the measured property. The largest groups are open; open the others as you need them.
total soil organic matter
↑ 3= 14
- increase
sugarcane systems (sole SG and SG + Bra) vs. native forest (NF)significant · 0–10 cm · Giasa Plant · 0–10 cm; both sugarcane systems, with long-term vinasse.
Source · p. 9 “Soil total organic matter (TOM, Figure 5) in the 0–10 cm surface layer was higher (p \< 0.05) by about 76% for sugarcane (sole SG) and sugarcane + Brachiaria intercrop (SG + Bra) compared with native forest (NF).”
- increase
SG + Bra intercrop vs. native forest (NF)significant · 10–20 cm · 10–20 cm
Source · p. 9 “In the 10–20 cm layer, SG + Bra soil had the highest (p \< 0.05) TOM compared with both SG (by 64%) and NF (by 79%).”
- increase
SG + Bra intercrop vs. sole sugarcane (SG)significant · 10–20 cm · 10–20 cm
Source · p. 9 “In the 10–20 cm layer, SG + Bra soil had the highest (p \< 0.05) TOM compared with both SG (by 64%) and NF (by 79%).”
- no effect
sugarcane systems (sole SG and SG + Bra) vs. native forest (NF)not significant · 20–40 cm · 20–40 cm; Fig5 all uppercase A.
Source · p. 9 “For the deeper 20–40 cm layer, there was no significant difference (p \> 0.05) in SOM”
saturated hydraulic conductivity
↓ 2= 24
- decrease
sugarcane systems (sole SG and SG + Bra) vs. native forest (NF)significant · 0–10 cm · 0–10 cm; both sugarcane systems A vs NF B.
Source · p. 10 “with the NF having a Ksat about five and nine times those of sole SG and SG + Bra intercrop, respectively.”
- decrease
SG + Bra intercrop vs. native forest (NF)significant · 10–20 cm · 10–20 cm; Bra A vs NF B, sole SG AB excluded.
Source · p. 10 “For the 10–20 cm subsurface layer, NF also had the highest Ksat, about two and three times that of sole SG and SG + Bra intercrop, respectively, although the difference between the NF and sole SG was not significant (p \> 0.05).”
- no effect
sugarcane systems (sole SG and SG + Bra) vs. native forest (NF)not significant · 20–40 cm · 20–40 cm; all A.
Source · p. 10 “For the deeper 20–40 cm layer, the Ksat was lowest under NF by about 5 and 11% compared with sole SG and SG + Bra intercrop, respectively; however, the difference was not significant (p \> 0.05).”
- no effect
SG + Bra intercrop vs. sole sugarcane (SG)not significant · 0–40 cm · 0–40 cm; Fig7 shared pair letters.
Source · p. 26 “Intercropping sugarcane with Brachiaria ruziziensis did not lead to significant short-term improvements in either conventionally measured or X-ray computed tomography-derived soil physical parameters when compared with sole sugarcane.”
pore anisotropy
↑ 2= 24
- increase
sole sugarcane (SG) vs. native forest (NF)significant · 0–20 cm · 0–20 cm; Fig15 SG B versus NF A.
Source · p. 18 “Pore anisotropy (Figure 15a) in the 0–10 and 10–20 cm layers was significantly higher (p \< 0.05) in sole SG compared with NF and SG + Bra intercrop”
- increase
SG + Bra intercrop vs. native forest (NF)significant · 10–20 cm · 10–20 cm; Fig15 intercrop B versus NF A; surface AB excluded.
Source · p. 24 “The higher degree of anisotropy observed for both sole SG and SG + Bra intercrop compared with the NF shows more anisotropy behavior.”
- no effect
SG + Bra intercrop vs. sole sugarcane (SG)not significant · 0–40 cm · 0–40 cm; Fig15 shared uppercase pair letters.
Source · p. 18 “the difference in anisotropy between sole SG and SG + Bra intercrop was not significant (p \> 0.05).”
- no effect
sugarcane systems (sole SG and SG + Bra) vs. native forest (NF)not significant · 20–40 cm · 20–40 cm; Fig15 all A.
Source · p. 18 “For the 20–40 cm layer, there was no significant difference (p \> 0.05) in anisotropy among the NF and sugarcane cropping systems.”
total nitrogen
↑ 2= 13
- increase
sugarcane systems (sole SG and SG + Bra) vs. native forest (NF)significant · 0–10 cm · 0–10 cm; both sugarcane systems.
Source · p. 10 “Soil total nitrogen (TN) in the 0–10 cm surface layer of the native forest (NF) was lower (p \< 0.05) by about 65% compared to both sole SG and SG + Bra intercrop.”
- increase
SG + Bra intercrop vs. native forest (NF)significant · 10–20 cm · 10–20 cm; Fig6 Bra B, NF A; sole SG A excluded.
Source · p. 10 “In the 10–20 cm layer, the NF had a TN lower than sole SG and SG + Bra intercrop by 23 and 224%, respectively.”
- no effect
sugarcane systems (sole SG and SG + Bra) vs. native forest (NF)not significant · 20–40 cm · 20–40 cm; both sugarcane systems.
Source · p. 10 “For the deeper 20–40 cm layer, there was no significant difference (p \> 0.05) in TN”
bulk density
↑ 1= 23
- no effect
sugarcane systems (sole SG and SG + Bra) vs. native forest (NF)not significant · 0–20 cm · 0–20 cm; actual Fig7 A letters override misprinted p<.05 next to did not differ.
Source · p. 10 “Soil bulk density (BD, Figure 7) of both the 0–10 and 10–20 cm layers did not differ (p \< 0.05) among the sugarcane cropping systems and native forest”
- increase
sole sugarcane (SG) vs. native forest (NF)significant · 20–40 cm · 20–40 cm; SG B vs NF A; intercrop AB excluded from significant increase.
Source · p. 10 “For the 20–40 cm layer, sole SG and SG + Bra intercrop had a higher (p \< 0.05) BD than that of the NF by about 13 and 10%, respectively.”
- no effect
SG + Bra intercrop vs. sole sugarcane (SG)not significant · 0–40 cm · 0–40 cm; shared uppercase letters, Fig7.
Source · p. 21 “The non-significant influence of intercropping Brachiaria with sugarcane on BD”
CT total porosity
↓ 33
- decrease
SG + Bra intercrop vs. sole sugarcane (SG)significant · 0–10 cm · 0–10 cm; CT, A vs B.
Numbers
- treatment 0.13 vs. control 0.197 mm3 mm−3 (-34.01 %)
Source · p. 15 “Soil porosity derived from X-ray computed tomography (CT-porosity, Table 3) was reduced (p \< 0.05) in the 0–10 cm surface layer for intercropping sugarcane with Brachiaria compared with both NF (38%) and sole SG (34%).”
- decrease
SG + Bra intercrop vs. native forest (NF)significant · 0–10 cm · 0–10 cm; CT.
Numbers
- treatment 0.13 vs. control 0.209 mm3 mm−3 (-37.8 %)
Source · p. 15 “Soil porosity derived from X-ray computed tomography (CT-porosity, Table 3) was reduced (p \< 0.05) in the 0–10 cm surface layer for intercropping sugarcane with Brachiaria compared with both NF (38%) and sole SG (34%).”
- decrease
sugarcane systems (sole SG and SG + Bra) vs. native forest (NF)significant · 10–40 cm · 10–40 cm; Table3 values/letters contradict prose higher at10–20. Both sugarcane A versus NF B.
Numbers
- treatment 0.113 vs. control 0.232 mm3 mm−3 (-51.29 %) · 10–20 cm · sole SG
- treatment 0.135 vs. control 0.232 mm3 mm−3 (-41.81 %) · 10–20 cm · SG+Bra
- treatment 0.137 vs. control 0.209 mm3 mm−3 (-34.45 %) · 20–40 cm · sole SG
- treatment 0.138 vs. control 0.209 mm3 mm−3 (-33.97 %) · 20–40 cm · SG+Bra
Source · p. 15 “| Cropping system | Total porosity, mm 3 mm − 3 | | | | NF | 0.209 aB | 0.232 aB | 0.209 aB | | SG | 0.197 bB | 0.113 aA | 0.137 aA | | SG + Bra | 0.130 aA | 0.135 aA | 0.138 aA |”
total porosity from SWRC
↑ 1= 12
- increase
sole sugarcane (SG) vs. native forest (NF)significant · 0–10 cm · 0–10 cm; saturation-derived; SG B versus NF A. Bra AB not significant.
Numbers
- treatment 0.549 vs. control 0.392 m3 m−3 (+40.05 %) · 0–10 cm
Source · p. 13 “Soil total porosity (Pt, measured as the saturation water content—Table 2)”
Source · p. 13 “| Pt | NF | 0.392 aA | 0.424 aA | 0.468 aA | | | | SG | 0.549 bB | 0.465 abA | 0.402 aA | 0.031 |”
- no effect
sugarcane systems (sole SG and SG + Bra) vs. native forest (NF)not significant · 10–40 cm · 10–40 cm; Table2 all A.
Source · p. 13 “In the 10–20 and 20–40 cm layers, there were no differences (p \< 0.05) in Pt between the sugarcane cropping systems and native forest”
pore connectivity
↓ 1= 12
- decrease
sugarcane systems (sole SG and SG + Bra) vs. native forest (NF)significant · 0–40 cm · 0–40 cm; both sugarcane systems; Fig15 A vs NF B.
Source · p. 18 “Pore connectivity (Figure 15b) as revealed by X-ray computed tomography was significantly higher (p \< 0.05) in the NF in all the soil layers compared with the sugarcane cropping systems.”
- no effect
SG + Bra intercrop vs. sole sugarcane (SG)not significant · 0–40 cm · 0–40 cm; Fig15 SG and intercrop all A.
Source · p. 25 “the lack of significant differences between SG + Bra and sole SG indicates that, within the two-year timeframe and at the planting density used, Brachiaria primarily altered pore redistribution rather than creating new, continuous macropore networks.”
macroporosity from SWRC
= 11
- no effect
sugarcane systems (sole SG and SG + Bra) vs. native forest (NF)not significant · 0–40 cm · 0–40 cm; SWRC-derived macroporosity; Table2 all A.
Source · p. 13 “Soil macroporosity (Mac, Table 2) did not differ (p \> 0.05) between the sugarcane cropping systems and native forest in the three layers”
microporosity from SWRC
↑ 11
- increase
sugarcane systems (sole SG and SG + Bra) vs. native forest (NF)significant · 0–20 cm · 0–20 cm; both sugarcane systems; Table2 B vs A.
Numbers
- treatment 0.355 vs. control 0.125 m3 m−3 (+184 %) · 0–10 cm · sole SG
- treatment 0.212 vs. control 0.096 m3 m−3 (+120.8 %) · 10–20 cm · sole SG
- treatment 0.287 vs. control 0.125 m3 m−3 (+129.6 %) · 0–10 cm · SG + Bra
- treatment 0.259 vs. control 0.096 m3 m−3 (+169.8 %) · 10–20 cm · SG + Bra
Source · p. 13 “Both sole SG and SG + Bra_intercrop had higher (p \< 0.05) soil microporosity (Mic, Table 2) than the NF in both the 0–10 and 10–20 cm layers”
field capacity
↑ 11
- increase
sugarcane systems (sole SG and SG + Bra) vs. native forest (NF)significant · 0–20 cm · 0–20 cm; both sugarcane systems; Table2.
Numbers
- treatment 0.333 vs. control 0.102 m3 m−3 (+226.5 %) · 0–10 cm · sole SG
- treatment 0.188 vs. control 0.069 m3 m−3 (+172.5 %) · 10–20 cm · sole SG
- treatment 0.261 vs. control 0.102 m3 m−3 (+155.9 %) · 0–10 cm · SG + Bra
- treatment 0.237 vs. control 0.069 m3 m−3 (+243.5 %) · 10–20 cm · SG + Bra
Source · p. 14 “Soil water content at field capacity (FC, Table 2) of both the 0–10 and 10–20 cm layers was higher (p \< 0.05) in the SG and SG + Bra intercrop compared with NF.”
plant available water
↑ 11
- increase
sugarcane systems (sole SG and SG + Bra) vs. native forest (NF)significant · 0–20 cm · 0–20 cm; both sugarcane systems; Table2.
Numbers
- treatment 0.142 vs. control 0.049 m3 m−3 (+189.8 %) · 0–10 cm · sole SG
- treatment 0.091 vs. control 0.043 m3 m−3 (+111.6 %) · 10–20 cm · sole SG
- treatment 0.149 vs. control 0.049 m3 m−3 (+204.1 %) · 0–10 cm · SG + Bra
- treatment 0.094 vs. control 0.043 m3 m−3 (+118.6 %) · 10–20 cm · SG + Bra
Source · p. 14 “Soil available water (AW, Table 2) was significantly lower (p \< 0.05) in the 0–10 and 10–20 cm layers of the NF compared with both sugarcane cropping systems.”
CT macroporosity
↓ 11
- decrease
sugarcane systems (sole SG and SG + Bra) vs. native forest (NF)significant · 0–40 cm · 0–40 cm; CT; both sugarcane systems.
Source · p. 15 “Soil macroporosity derived by X-ray computed tomography (CT-Mac, Table 3) was higher (p \< 0.05) in the NF compared with both sole SG and SG + Bra intercrop in all three layers by 30%–55%.”
fractal dimension
↓ 11
- decrease
sugarcane systems (sole SG and SG + Bra) vs. native forest (NF)significant · 0–20 cm · 0–20 cm; Fig15 NF B vs both crops A.
Source · p. 18 “Fractal dimension (Figure 15c) showed NF had the highest (p \< 0.05) value in both 0–10 and 10–20 cm layers in comparison to both SG and SG + Bra intercrop”
Set-up
Treatments
- land use and cover crop intercropping
- native forest (NF)Broad-leaved forestsole sugarcane (SG)Sugar cane/Saccharum officinarumSG + Bra intercropIntercroppingsugarcane systems (sole SG and SG + Bra)Sugar cane/Saccharum officinarum
Measured
- total soil organic matterSoil organic matter
- Unit
- %
- Method
- Dry oxidation
- total nitrogen
- Unit
- %
- bulk density
- Unit
- g cm−3
- saturated hydraulic conductivity
- Unit
- cm h−1
- Method
- constant-head
- total porosity from SWRCTotal porosity
- Unit
- m3 m−3
- Method
- saturation water content
- macroporosity from SWRCMacroporosity
- Unit
- m3 m−3
- Method
- saturation minus water content at −6 kPa
- microporosity from SWRCMicroporosity
- Unit
- m3 m−3
- Method
- water content at −6 kPa
- field capacityVolumetric water content at field capacity
- Unit
- m3 m−3
- Method
- water content at −10 kPa
- plant available water
- Unit
- m3 m−3
- Method
- FC minus PWP at −1500kPa
- CT total porosityTotal porosity
- Unit
- mm3 mm−3
- Method
- X-ray CT
- CT macroporosityMacroporosity
- Unit
- mm3 mm−3
- Method
- X-ray CT
- pore anisotropy
- Method
- X-ray CT
- pore connectivity
- Method
- X-ray CT
- fractal dimension
- Method
- X-ray CT
Sites
Giasa Plant
- Location
- Pedras de Fogo, Paraíba, Brazil7.35° S, 35.03° W
- Climate
- AS
- Soil
- Quartzipsamments · USDA
- Land use
- sugarcane fieldArable land
| Depth | Texture | Clay | pH | Organic C | Bulk density |
|---|---|---|---|---|---|
| 0–25 cm | – | – | 5.3 | – | – |
| 25–50 cm | – | – | 4.8 | – | – |
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