Agronomy · 2026
Chlorella vulgaris Enhances Soil Aggregate Stability in Rice Paddy Fields and Arable Land Through Alterations in Soil Extracellular Polymeric Substances
Huang, S., Jiang, X., Liu, H., Jiang, H., Cheng, J., Jiang, H., Yu, S., Chen, S.
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Chlorella vulgaris Enhances Soil Aggregate Stability in Rice…
Abstract
Microalgal amendments can improve soil structure by regulating extracellular polymeric substances (EPSs). However, the mechanisms underlying this process in red soils (characterized by high clay content and susceptibility to acidification) under different farming practices remain unclear. This study examined how Chlorella vulgaris (C. vulgaris) amendment influences EPS composition to enhance soil aggregate stability under arable land and rice paddy farming. A five-month pot experiment using a completely randomized design was conducted to investigate the effects of Chlorella vulgaris amendment on soils cultivated with Pennisetum × sinese and rice, two economically important crops commonly grown in South China. At the end of the experiment, Chlorella vulgaris amendment substantially increased both the mean weight diameter (MWD) and geometric mean diameter (GMD) of soil aggregates under both farming systems. Excitation–emission matrix (EEM) fluorescence spectroscopy revealed distinct changes in soil EPS components between the two farming types. Under arable land farming, humic-like and protein-like EPSs were dominant in Chlorella vulgaris-amended treatments, with fluorescence intensities more than doubling compared to the control. Conversely, under rice paddy farming, soil fulvic acid was the main component and showed a moderate increase. Partial least squares path modeling (PLS-PM) demonstrated that protein-like and humic-like EPSs had the strongest direct effects on aggregate stability in arable land red soil, while fulvic acid was the key factor in rice paddy red soil. The present study demonstrates that Chlorella vulgaris amendment improves aggregate stability in red soils through farming-specific, EPS-mediated pathways, providing a quantitative framework for researchers and land managers seeking to apply microalgal amendments for red soil enhancement and sustainable land management.
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Microalgal amendments can improve soil structure by regulating extracellular polymeric substances (EPSs). However, the mechanisms underlying this process in red soils (characterized by high clay content and susceptibility to acidification) under different farming practices remain unclear. This study examined how Chlorella vulgaris (C. vulgaris) amendment influences EPS composition to enhance soil aggregate stability under arable land and rice paddy farming. A five-month pot experiment using a completely randomized design was conducted to investigate the effects of Chlorella vulgaris amendment on soils cultivated with Pennisetum × sinese and rice, two economically important crops commonly grown in South China. At the end of the experiment, Chlorella vulgaris amendment substantially increased both the mean weight diameter (MWD) and geometric mean diameter (GMD) of soil aggregates under both farming systems. Excitation–emission matrix (EEM) fluorescence spectroscopy revealed distinct changes in soil EPS components between the two farming types. Under arable land farming, humic-like and protein-like EPSs were dominant in Chlorella vulgaris-amended treatments, with fluorescence intensities more than doubling compared to the control. Conversely, under rice paddy farming, soil fulvic acid was the main component and showed a moderate increase. Partial least squares path modeling (PLS-PM) demonstrated that protein-like and humic-like EPSs had the strongest direct effects on aggregate stability in arable land red soil, while fulvic acid was the key factor in rice paddy red soil. The present study demonstrates that Chlorella vulgaris amendment improves aggregate stability in red soils through farming-specific, EPS-mediated pathways, providing a quantitative framework for researchers and land managers seeking to apply microalgal amendments for red soil enhancement and sustainable land management.
Microalgal amendments can improve soil structure by regulating extracellular polymeric substances (EPSs). However, the mechanisms underlying this process in red soils (characterized by high clay content and susceptibility to acidification) under different farming practices remain unclear. This study examined how Chlorella vulgaris (C. vulgaris) amendment influences EPS composition to enhance soil aggregate stability under arable land and rice paddy farming. A five-month pot experiment using a completely randomized design was conducted to investigate the effects of Chlorella vulgaris amendment on soils cultivated with Pennisetum × sinese and rice, two economically important crops commonly grown in South China. At the end of the experiment, Chlorella vulgaris amendment substantially increased both the mean weight diameter (MWD) and geometric mean diameter (GMD) of soil aggregates under both farming systems. Excitation–emission matrix (EEM) fluorescence spectroscopy revealed distinct changes in soil EPS components between the two farming types. Under arable land farming, humic-like and protein-like EPSs were dominant in Chlorella vulgaris-amended treatments, with fluorescence intensities more than doubling compared to the control. Conversely, under rice paddy farming, soil fulvic acid was the main component and showed a moderate increase. Partial least squares path modeling (PLS-PM) demonstrated that protein-like and humic-like EPSs had the strongest direct effects on aggregate stability in arable land red soil, while fulvic acid was the key factor in rice paddy red soil. The present study demonstrates that Chlorella vulgaris amendment improves aggregate stability in red soils through farming-specific, EPS-mediated pathways, providing a quantitative framework for researchers and land managers seeking to apply microalgal amendments for red soil enhancement and sustainable land management.
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.
MWD
↑ 1= 12
- increase
active C. vulgaris vs. CK—blank controlsignificant · 0–15 cm · Institute of Eco-environmental and Soil Sciences greenhouse; soil from Zengcheng District · Arable Z5/Z10/Z20, paddy Z10/Z20 vs CK; final sampling
Source · p. 6 “Active C. vulgaris addition significantly enhanced aggregate stability indices and increased macroaggregate proportions in both farming systems”
- no effect
ZL—heat-inactivated C. vulgaris suspension vs. CK—blank controlnot significant · 0–15 cm · Institute of Eco-environmental and Soil Sciences greenhouse; soil from Zengcheng District · Both farming systems, final sampling; ZL and CK share letters in Figure1
Source · p. 14 “while heat-inactivated treatment showed no effect;”
Source · p. 6 “with no significant effect from heat-inactivated treatment.”
GMD
↑ 1= 12
- increase
active C. vulgaris vs. CK—blank controlsignificant · 0–15 cm · Institute of Eco-environmental and Soil Sciences greenhouse; soil from Zengcheng District · Arable Z5/Z10/Z20; paddy Z10 only vs CK, final sampling; Figure1 letters qualify broad text
Source · p. 6 “Active C. vulgaris addition significantly enhanced aggregate stability indices and increased macroaggregate proportions in both farming systems”
- no effect
ZL—heat-inactivated C. vulgaris suspension vs. CK—blank controlnot significant · 0–15 cm · Institute of Eco-environmental and Soil Sciences greenhouse; soil from Zengcheng District · Both farming systems, final sampling
Source · p. 6 “ZL showed no significant effect on GMD or R0.25 compared to CK”
R0.25
↑ 1= 12
- increase
active C. vulgaris vs. CK—blank controlsignificant · 0–15 cm · Institute of Eco-environmental and Soil Sciences greenhouse; soil from Zengcheng District · Arable Z5/Z10/Z20, paddy Z10/Z20 vs CK; final sampling
Source · p. 6 “Active C. vulgaris addition significantly enhanced aggregate stability indices and increased macroaggregate proportions in both farming systems”
- no effect
ZL—heat-inactivated C. vulgaris suspension vs. CK—blank controlnot significant · 0–15 cm · Institute of Eco-environmental and Soil Sciences greenhouse; soil from Zengcheng District · Both farming systems, final sampling
Source · p. 6 “ZL showed no significant effect on GMD or R0.25 compared to CK”
OM
↑ 11
- increase
active C. vulgaris vs. CK—blank controlsignificant · 0–15 cm · Institute of Eco-environmental and Soil Sciences greenhouse; soil from Zengcheng District · Z20 vs CK, both farming systems; March–July2024, final sampling
Numbers
- treatment 31.03 vs. control 21.21 g/kg (+46.3 %) · arable Z20
- treatment 39.28 vs. control 29.51 g/kg (+33.11 %) · paddy Z20
Source · p. 5 “In arable land, OM under Z20 was 46.30% higher than CK”
Source · p. 5 “Z20 increased OM by 33.11% compared to CK”
TN
↑ 11
- increase
active C. vulgaris vs. CK—blank controlsignificant · 0–15 cm · Institute of Eco-environmental and Soil Sciences greenhouse; soil from Zengcheng District · Z20 vs CK, both farming systems; final sampling. Arable TN values printed unusually high; no correction inferred.
Numbers
- treatment 22.31 vs. control 17.76 g/kg (+25.62 %) · arable Z20
- treatment 1.98 vs. control 1.27 g/kg (+55.91 %) · paddy Z20
Source · p. 5 “Across both farming systems, OM, TN, TP, AP, AK, and pH increased significantly with higher C. vulgaris addition rates”
TP
↑ 11
- increase
active C. vulgaris vs. CK—blank controlsignificant · 0–15 cm · Institute of Eco-environmental and Soil Sciences greenhouse; soil from Zengcheng District · Z20 vs CK in both farming systems, final sampling
Numbers
- treatment 2.01 vs. control 1.03 g/kg (+95.15 %) · arable Z20
- treatment 2.38 vs. control 1.56 g/kg (+52.56 %) · paddy Z20
Source · p. 5 “Across both farming systems, OM, TN, TP, AP, AK, and pH increased significantly with higher C. vulgaris addition rates”
AP
↑ 11
- increase
active C. vulgaris vs. CK—blank controlsignificant · 0–15 cm · Institute of Eco-environmental and Soil Sciences greenhouse; soil from Zengcheng District · Z20 vs CK in both farming systems; final sampling
Numbers
- treatment 0.23 vs. control 0.12 g/kg (+91.67 %) · arable Z20
- treatment 0.15 vs. control 0.11 g/kg (+36.36 %) · paddy Z20
Source · p. 5 “Across both farming systems, OM, TN, TP, AP, AK, and pH increased significantly with higher C. vulgaris addition rates”
AK
↑ 11
- increase
active C. vulgaris vs. CK—blank controlsignificant · 0–15 cm · Institute of Eco-environmental and Soil Sciences greenhouse; soil from Zengcheng District · Arable Z20 and paddy Z5 vs CK; final sampling. Paddy Z10/Z20 not significant.
Numbers
- treatment 0.83 vs. control 0.44 g/kg (+88.64 %) · arable Z20
- treatment 0.37 vs. control 0.23 g/kg (+60.87 %) · paddy Z5
Source · p. 5 “Across both farming systems, OM, TN, TP, AP, AK, and pH increased significantly with higher C. vulgaris addition rates”
pH
↑ 11
- increase
active C. vulgaris vs. CK—blank controlsignificant · 0–15 cm · Institute of Eco-environmental and Soil Sciences greenhouse; soil from Zengcheng District · Z20 vs CK, both systems, final sampling
Numbers
- treatment 6.23 vs. control 4.81 (+29.52 %) · arable Z20
- treatment 5.43 vs. control 4.97 (+9.256 %) · paddy Z20
Source · p. 5 “Soil pH under Z20 was significantly higher than CK in both arable land”
Source · p. 6 “and rice paddies (p = 0.005).”
MBC
↑ 11
- increase
active C. vulgaris vs. CK—blank controlsignificant · 0–15 cm · Institute of Eco-environmental and Soil Sciences greenhouse; soil from Zengcheng District · Arable Z10/Z20; paddy Z5/Z10/Z20 vs CK; final sampling
Numbers
- percent_change 64.67 · arable Z20
- percent_change 25.53 · paddy Z20
Source · p. 6 “MBC and MBN increased with higher C. vulgaris addition rates in both farming systems (Figure 3).”
MBN
↑ 11
- increase
active C. vulgaris vs. CK—blank controlsignificant · 0–15 cm · Institute of Eco-environmental and Soil Sciences greenhouse; soil from Zengcheng District · Z5/Z10/Z20 vs CK, both farming systems; final sampling
Numbers
- percent_change 215.9 · arable Z20
- percent_change 134.5 · paddy Z20
Source · p. 6 “MBC and MBN increased with higher C. vulgaris addition rates in both farming systems (Figure 3).”
EPS humic-like fluorescence intensity
↑ 11
- increase
active C. vulgaris vs. CK—blank controlsignificant · 0–15 cm · Institute of Eco-environmental and Soil Sciences greenhouse; soil from Zengcheng District · Arable only, C1; Z5/Z10/Z20 vs CK, final sampling
Source · p. 9 “In arable land, C. vulgaris addition significantly increased the fluorescence intensity of all three components”
Source · p. 7 “C1 = humic-like substances;”
EPS fulvic-like fluorescence intensity
↑ 11
- increase
active C. vulgaris vs. CK—blank controlsignificant · 0–15 cm · Institute of Eco-environmental and Soil Sciences greenhouse; soil from Zengcheng District · Arable C2 Z5/Z20; paddy C1 all active vs CK, final sampling; arable Z10 shares letter with CK
Source · p. 9 “In arable land, C. vulgaris addition significantly increased the fluorescence intensity of all three components”
Source · p. 9 “In rice paddies, C. vulgaris addition significantly increased C1 fluorescence intensity and its relative proportion”
EPS protein-like fluorescence intensity
↑ 11
- increase
active C. vulgaris vs. CK—blank controlsignificant · 0–15 cm · Institute of Eco-environmental and Soil Sciences greenhouse; soil from Zengcheng District · Arable only C3, Z5/Z10/Z20 vs CK, final sampling
Source · p. 9 “In arable land, C. vulgaris addition significantly increased the fluorescence intensity of all three components”
Source · p. 7 “C3 = protein-like substances.”
EPS-carbohydrates (EPS-C)
↑ 11
- increase
active C. vulgaris vs. CK—blank controlsignificant · 0–15 cm · Institute of Eco-environmental and Soil Sciences greenhouse; soil from Zengcheng District · Arable Z5/Z20; paddy Z5/Z10/Z20 vs CK; final sampling. EPS-C denotes carbohydrates. Arable Z10 and ZL share control letters.
Numbers
- percent_change 63.64 · arable Z20
- percent_change 48.65 · paddy Z5
- percent_change 25.76 · paddy Z10
- percent_change 53.26 · paddy Z20
Source · p. 11 “Active C. vulgaris addition increased both EPS-C and EPS-N content”
EPS-proteins (EPS-N)
↑ 11
- increase
active C. vulgaris vs. CK—blank controlsignificant · 0–15 cm · Institute of Eco-environmental and Soil Sciences greenhouse; soil from Zengcheng District · Paddy Z20 vs CK only, final sampling. EPS-N denotes proteins. Figure6 letters do not support arable increase despite prose.
Source · p. 11 “Active C. vulgaris addition increased both EPS-C and EPS-N content”
Set-up
Treatments
- Chlorella vulgaris amendmentMicrobial inoculant
- active C. vulgarisMicrobial inoculantCK—blank controlNo microbial inoculationZL—heat-inactivated C. vulgaris suspensionOrganic fertilizer
Measured
- OMSoil organic matter
- Unit
- g/kg
- Method
- colorimetry
- TNTotal Nitrogen
- Unit
- g/kg
- TPTotal Phosphorus
- Unit
- g/kg
- Method
- Mo-Sb colorimetric
- APAvailable phosphorus
- Unit
- g/kg
- AKExchangeable/available potassium
- Unit
- g/kg
- pH
- MWDWater-stable aggregate mean weight diameter (MWD)
- Unit
- mm
- GMDAggregate geometric mean diameter
- Unit
- mm
- R0.25Water-stable macroaggregates
- Unit
- %
- >2 mm macroaggregate proportionWater-stable macroaggregates
- Unit
- %
- MBCMicrobial biomass Carbon
- Unit
- mg/kg
- MBNMicrobial biomass Nitrogen
- Unit
- mg/kg
- EPS humic-like fluorescence intensityHumic substance carbon
- Unit
- RU
- Method
- CER extraction; EEM-PARAFAC fluorescence, semi-quantitative humic-like component
- EPS fulvic-like fluorescence intensityFulvic acid carbon
- Unit
- RU
- Method
- CER extraction; EEM-PARAFAC fluorescence, semi-quantitative fulvic-like component
- EPS protein-like fluorescence intensityProtein-like compounds
- Unit
- RU
- Method
- CER extraction; EEM-PARAFAC fluorescence
- EPS-carbohydrates (EPS-C)Extracellular polymeric substance saccharide
- Unit
- µg/g
- Method
- CER extraction; Figure6 axis defines EPS-C as carbohydrates, not elemental carbon
- EPS-proteins (EPS-N)Soil protein content
- Unit
- µg/g
- Method
- CER extraction; Figure6 axis defines EPS-N as proteins, not elemental nitrogen
Sites
Institute of Eco-environmental and Soil Sciences greenhouse; soil from Zengcheng District
- Location
- Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences23.18° N, 113.36° EZengcheng District, Guangzhou City, Guangdong Province (soil collection)
- Climate
- 21–22 °C mean annual temperature1,500 mm annual precipitation
- Soil
- red soil · Chinese
- Management on the whole site
- farmyard manureManure
| Depth | Texture | Clay | pH | Organic C | Bulk density |
|---|---|---|---|---|---|
| 0–20 cm | – | – | 5.07 | 20.7 g/kg | – |
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