Vegetation growth promotion and overall strength improvement using biopolymers in vegetated soils

Planting vegetation is a sustainable and eco-friendly method for shallow slope stabilization. However, in water-limited regions, this method is facing challenges such as retarded vegetation growth, which leads to unprotected soils. Biopolymers, with potentials in both vegetation growth promotion and soil strength enhancement, are therefore tested in this study with regard to their possibility in assisting soil reinforcement with vegetation through vegetation cultivation and direct shear tests. Both sugar-based and protein-based biopolymers improved water availability to growing plants and nutrient uptake. The most suitable polysaccharide xanthan gum was adopted to further explore the effects of treatment conditions (i.e., blending content) and external environment (i.e., precipitation) on the vegetated soil performance. Under a variety of water supplies, xanthan gum with a medium blending content of 0.5% (i.e., with respect to dry soil mass) led to the most substantial improvement in the ability to resist shear loading. This indicates that the appropriate dosage of biopolymers used at the initial stage of plant growth should provide moderate bond strength between soil particles, while not impeding root penetration. Supported by the obtained results, biopolymers are suggested to be used in combination with plants for soil reinforcement for the best efficiency.