Paradelo, Herbón and Barral make urban soil visible as functional infrastructure. Studying sixty-four soils across different parent materials and land uses in Santiago de Compostela, they measure bulk density, porosity, water-holding capacity, aggregate stability, permeability, penetration resistance and erosion risk. Their key contribution is to show that “urban soil” is not a uniform degraded category: properties are heterogeneous and strongly conditioned by management. Compaction is widespread, yet urban agriculture can retain higher permeability and lower compaction than grasslands or forests, while coarse fragments may sustain preferential infiltration despite local degradation. Methodologically, field and laboratory measurements connect microscopic physical structure to city-scale water-cycle performance. The wider bridge reaches urban ecology and landscape architecture: soil sealing, organic matter, desire lines and maintenance practices become design variables. Ground is therefore not a passive substrate beneath urban form but a dynamic medium regulating infiltration, erosion, vegetation and hydrological resilience.
