Optimization Vetiver Root Growth Using Modular and Root Biostimulants Combination in Soil Bioengineering Method for Slope Reinforcement

Abstract

The degradation of slope stability caused by earth-cutting activities during highway construction is a geotechnical problem that requires systematic, sustainable management. Conventional concrete-based slope stabilization methods, while structurally effective, generate significant CO₂ emissions, thereby contradicting the principles of sustainable development. This study aims to examine the effectiveness of soil bioengineering methods that integrate vetiver (Chrysopogon zizanioides) with modular jute fiber geotextiles, arbuscular mycorrhizal fungi (AMF) biostimulants, and soil moisture control to optimize root system development for slope stabilization. The study was conducted on a laboratory scale with eight treatment combinations covering variations in the use of jute fiber modular units, application of mycorrhizal biostimulants, and two soil moisture regimes (25–35% and 35–45%), with observations at 30, 60, and 90 days after planting (DAP). The parameters analyzed included vegetation biometrics, side root area ratio (RAR_side), root tensile strength, and shear strength of vegetated soil. The results showed that the combination of jute fiber modules and a mycorrhizal biostimulant produced the highest root growth response, with root length reaching ±54 cm and RAR values up to 29% at 90 DAP, and a strong positive correlation between root length and RAR_side (R² = 0.9216). The highest root tensile strength was obtained in the treatment combining modular geotextiles and a mycorrhizal biostimulant at a soil moisture content of 25–35%, reaching 72.5 MPa at a root diameter of 0.4 mm. At 90 days after sowing, treatment A1 achieved the highest cohesion value of 7.70 ± 0.32 kPa, with a root weight of 4.24 ± 0.07 grams, representing an increase of approximately 3.6 times compared to the control. The research results indicate that synergy among modular geotextiles, mycorrhizal biostimulants, and optimal moisture management has the potential to be an effective, environmentally friendly slope-stabilization solution for highway infrastructure projects in Indonesia.