Soil & Water Res., X:X | DOI: 10.17221/47/2025-SWR

Multi-objective optimisation and synergistic mechanisms of expansive soil improvement using organic fertiliser, slow-release fertiliser, and rice strawOriginal Paper

Yonggang Huang1*, Hongri Zhang2,3*, Xinzhong Wang1, Yuexing Wu1, Xianliang Tan1, Kang Xiong4
1 School of Civil Engineering, Hunan City University, Yiyang, Hunan, P.R. China
2 Guangxi Transportation Science & Technology Group Co., Ltd. Nanning, Guangxi, P.R. China
3 Shanghai Jiao Tong University, Shanghai, P.R. China
4 Huai'an Water Resources Survey and Design Institute Co., Ltd. Yiyang Branch, Yiyang, Hunan, P.R. China

This study systematically investigated the synergistic improvement of expansive soil using organic fertiliser (OF), slow-release fertiliser (SRF), and rice straw (RS) through Box-Behnken design (BBD) and response surface methodology (RSM). Key findings include: the quadratic models demonstrated high statistical significance (root density: R² = 0.765, F = 25.84; shear strength: R² = 0.885, F = 18.65; swelling rate: R² = 0.20, F = 15.23; all P < 0.001) with low prediction errors (root content: ± 0.08 mg/cm3; shear strength: ± 0.58 kPa; swelling rate: ± 0.38%); The combination of 12.30% OF + 0.7 kg/m3 SRF + 0.4% RS achieved 58% improvement in shear strength, 32% improvement in root content, 42.7% reduction in swelling rate; OF exhibited negative linear effects on root density (β = – 0.18, P = 0.002) with >10% dosage reducing root growth by 9.0%; SRF showed positive linear impacts on shear strength (β = +0.25, P = 0.001) and root density (β = + 0.12, P = 0.023); RS enhanced shear strength below 0.5% (β = + 0.08, P = 0.042) but impaired root density due to pore clogging (β = – 0.15, P = 0.008). The optimised formulation, validated by triplicate centre-point tests (coefficient of variation ≤ 2.1%), is recommended for slope stabilisation while limiting OF to ≤ 10% to prevent performance degradation. This data-driven approach provides actionable insights for balancing agricultural waste utilisation and geotechnical performance in expansive soil improvement.

Keywords: agricultural waste recycling; expansive soil; shear strength; swelling potential; synergistic effect; threshold effect

Received: April 21, 2025; Revised: October 15, 2025; Accepted: October 15, 2025; Prepublished online: January 4, 2026 

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    References

    1. Candiot L.V., De Z.M., Camara M.S., Goicechea H.C. (2014): Experimental design and multiple response optimization using the desirability function in analytical methods development. Talanta, 124: 123-138. Go to original source... Go to PubMed...
    2. Chen D.J., Wang G.Y., Ouyang M., Yang Y.Q. (2024): Experimental study on the influence of organic fertilizer application on expansive soil with vetiver grass planting [Online ahead of print]. Journal of China & Foreign Highway. Retrieved from http://kns.cnki.net/kcms/detail/43.1363.U.20240403.1548.002.html.
    3. Chen S., Huang J., Guo R., Ma H., Guo J., Ling N., Xu Q., Wang M., Shen Q., Guo S. (2025). Soil net carbon balance depends on soil C : N : P stoichiometry. Soil & Tillage Research, 245: 106298. Go to original source...
    4. Feng X.S., Xu G.Z., Ji F., Zhang D., Ding Y.X. (2020). Study on foundation bearing capacity considering the reinforcement effect of rice straw bundles. Sichuan Building Science, 46: 8.
    5. Fu C.L., Zeng Z.T., Mo H.Y. (2019): Experimental study on the engineering characteristics of lime-modified expansive soil. Journal of Guangxi University (Natural Science Edition), 44: 524-533.
    6. Fu J.L. (2018): Experimental Study on the Mechanical Characteristics of Expansive Soil Reinforced by Vetiver Root System [PhD. Thesis]. Changsha, Changsha University of Science and Technology.
    7. GB/T 50123-2019 (2019): Standard for Geotechnical Testing Method. Ministry of Housing and Urban-Rural Development of the People's Republic of China
    8. Huang Y.G., Rao Y.Z. (2016): Prediction of slope stability based on response surface method. Journal of Jiangxi University of Science and Technology, 37: 68-71.
    9. Huang Y.G., Deng P., Wang G.Y., Zhang H.R. (2024): Effects of vetiver root on cracking of expansive soils and its mechanistic analysis. Scientific Reports, 14: 19737. Go to original source... Go to PubMed...
    10. Jones L.D., Jefferson I. (2018): Global case studies of expansive soil problems. In: Petry T.M., Shackelford C.D. (eds.): Expansive Soils: Problems and Practice. London, ICE Publishing: 45-78.
    11. Li R.F., Wang G.Y., Zhang Y.J., Huang Y.G. (2020): Experimental study on the influence of vetiver root system planting on the characteristics of expansive soil. Journal of Highway and Transportation Research and Development, 37: 43-52.
    12. Lu L.D. (2022): Delaying application time of slow-release fertilizer increases soil rhizosphere nitrogen content, root activity, and grain yield of spring maize. Acta Agronomica Sinica (English Edition), 10: 1798-1806. Go to original source...
    13. Luo Y., Li G.H., Zhang H. (1996): Effects of organic cationic compounds on improving the properties of expansive soils. Chinese Journal of Geotechnical Engineering, 18: 40-44.
    14. Nelson J.D., Chao K.C., Overton D.D. (2015): Geotechnical Engineering for Transportation Projects. 1st Ed. Reston, American Society of Civil Engineers.
    15. Rao Y.Z., Huang Y.G. (2016): Study on optimization of blasting parameters based on response surface optimization method. Mining Research and Development, 36: 46-49.
    16. Su B.W., Zhang H., Zhang Y.L., Shao S.S., Mouazen A.M., Jiao H. (2023): Soil C : N : P stoichiometry succession and land use effect after intensive reclamation: A case study on the Yangtze River floodplain. Agronomy, 13: 1133. Go to original source...
    17. Wang C.S., Zhang G.H., Chen S.Q. (2024): Seasonal variations of soil functions affected by straw incorporation in croplands with different degradation degrees. Soil and Tillage Research, 246: 106789. Go to original source...
    18. Wang D.X., Zhang Z.W., Wang X.Q., Zhou W.L. (2022): Pavement performance and micro-mechanism of cement-modified expansive soil under dry-wet and freeze-thaw cycles. Journal of Central South University (Science and Technology), 53: 306-316.
    19. Wang G.Y., Huang Y.G., Li R.F., Chang J.M., Fu J.L. (2020a): Influence of vetiver root on strength of expansive soil-experimental study. PLoS ONE, 15: e0244818. Go to original source... Go to PubMed...
    20. Wang G.Y., Huang Y.G., Li R.F., Chang J.M., Fu J.L. (2020b): Influence of vetiver root system on mechanical performance of expansive soil: Experimental studies. Advances in Civil Engineering, 2020: 2027172. Go to original source...
    21. Wu H.L., Pan L.L., Xue G.Q., Gu H.D., Zhu N., Wang F., Tang Q. (2018): Effects of fiber reinforcement on mechanical properties of soil. Forest Engineering, 34: 80-86.
    22. Xu G.X., Wang Z.F., Gao M., Tian D., Huang R., Liu J., Li J.F. (2017): Effects of Straw and Biochar Return in Soil on Soil Aggregate and Carbon Sequestration. Huan Jing Ke Xue, 39: 355-362.
    23. Xu H.B., Song X.J., Wang P. (2019): Experimental study on the strength and deformation characteristics of cement-modified expansive soil. South-to-North Water Transfer and Water Science & Technology, 17: 172-177.
    24. Xue Z.F., Wang L., Zheng W.J. (2020): Shear characteristics of loess reinforced with agricultural waste straw. Journal of Yangtze River Scientific Research Institute, 37: 180-186.
    25. Yu H.P., Yu Z.H. (2017): Nutrient release characteristics of five fertilizers with different processes. Journal of Zhejiang Agricultural Sciences, 58: 1961-1964.
    26. Zhao X.L., E S. Z., Yuan J.H., Wu B.M., Shao Q., Zhao T.X., Lu G.B, Zhang P., Liu Y.N. (2024): Nutrient slow-release mechanisms of slow-release fertilizers and research progress. Journal of Ecological Industry Science and Phosphorus-Fluorine Engineering, 39: 42-48.
    27. Zhao Z.X., Ran C., Meng X.Y., Bai T.Q., Zhao M.M., Guo L.Y., Shao X.W., Geng Y.Q. (2023): Effects of straw returning on distribution of soil aggregates and content of organic carbon in saline-sodic rice areas. Journal of Jilin Agricultural University, 45: 582-591.

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