Functional performance of constructed technosols as a soil management solution for urban green infrastructure

Urban green infrastructure (UGI) requires functional soils, yet sourcing fertile topsoil and natural aggregates can create environmental trade-offs. This study evaluated the performance of waste-derived constructed Technosols for UGI using an 18-month mesocosm experiment under semi-arid urban conditions. Four Technosol mixtures were assembled from locally available waste streams, including excavated subsoil (ExS), crushed concrete (CC), green-waste compost (GWC), together with a sand-gravel control. Mesocosms were planted with Lavandula angustifolia and subjected to two irrigation regimes (6 vs 12 mm wk^-1). Physical, chemical, and biological soil indicators were measured and integrated into function-based performance scores. The ExS-rich loamy sand Technosol (TE; 35% ExS, 35% CC) improved key soil properties relative to the sand-gravel control. Bulk density by 0.18 g cm^-3, while microporosity (22.7 vs 8.4%) and plant-available water increased by 6.3%. Near-saturated hydraulic conductivity remained high (11 cm h^-1) relative to the sand-gravel control. TE also increased cation exchange capacity (29.4 vs 12.2 meq 100 g^-1) and soil organic carbon (31.2 vs 19.2 g kg^-1). Across mixtures, the higher irrigation regime increased shoot biomass by 26% and root biomass by 39%. Functional performance scores were higher in ExS-rich mixtures for nutrient provision, nutrient cycling, water regulation and carbon storage. These results show that replacing coarse mineral fractions with locally available excavated subsoil combined with recycled mineral materials and green-waste compost can rapidly develop key soil quality attributes in Technosols. Waste-derived Technosols therefore represent a promising strategy to design functional soils for semi-arid urban green infrastructure. Long-term field validation across vegetation types is needed to refine design thresholds and evaluate large-scale deployment.