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 like retarded vegetation growth, which leads to unprotected soils. Biopolymer, with potentials in both vegetation growth promotion and soil strength enhancement, is therefore tested in this paper with regard to its 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 condition (i.e., blending content) and external environment (i.e., precipitation) on the vegetated soil performances. Under a variety of water supply, 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 biopolymer used at the initial stage of plant growth, should provide moderate bond strength between soil particles, whilst not impeding root penetration. Supported by the obtained results, biopolymer is suggested to be used in combination with plants for soil reinforcement for the best efficiency.