Biochar-based mediation of urease-producing bacteria for enhanced sandy soil stabilization and plant growth adaptability

Wind erosion is a major driver of sandy soil degradation in arid and semi-arid regions. Improving soil structural stability while maintaining conditions favorable for vegetation establishment remains a key challenge for sandy-land management and revegetation. In this study, poorly graded sandy soil from Northwest China was treated with biochars (BCs) derived from corn straw, pine sawdust, and walnut shells, with or without H₂O₂ oxidative modification, in combination with microbially induced carbonate precipitation (MICP). Their effects on bacterial immobilization, CaCO₃ precipitation, soil mechanical properties, nutrient conservation, and plant growth were systematically evaluated. BC addition enhanced MICP performance by providing porous surfaces and active interfaces for urease-producing bacterial immobilization, reducing bacterial desorption, and promoting CaCO₃ precipitation and composite cementation. These effects improved soil strength, disintegration resistance, and nutrient retention. H₂O₂ modification further enhanced bacterial immobilization, CaCO₃ formation, and soil stabilization. However, stronger mineral cementation also increased root penetration resistance, limiting early germination and root elongation. Plant responses varied with BC feedstock. Modified pine sawdust and walnut shell BCs reduced aboveground and belowground biomass by 4.57–23.39% after 60 d, whereas modified corn straw BC decreased belowground biomass by only 3.27% while increasing aboveground biomass by 5.99%. Considering both structural stability and plant growth performance, oxidatively modified corn straw BC showed the best overall performance among the tested treatments. These findings demonstrate the potential of BC-assisted MICP for stabilizing sandy soil while maintaining plant growth under the tested conditions and provide a basis for its further evaluation as a wind-erosion-mitigation strategy in arid and semi-arid regions.