Enhancing stable Technosols formation through iron tailing-amended sludge composting and plant colonization

Soil is a non-renewable resource essential for environmental sustainability and food production. Intensive human activities have consumed vast land resources, promoting development of Technosols-engineered soil-like materials produced from organic and mineral wastes. However, most Technosols have limited structural stability and carbon sequestration capacity. Here, we propose a route to form stable Technosols through co-composting of iron tailings (IT) and waste sludge followed by pioneer plant colonization, and investigated underlying mechanisms. Fresh organic fractions in sludge promoted water-stable macroaggregate formation during composting, while IT supplied Fe/Al-bearing minerals for structural consolidation. Pioneer plant colonization stimulated rhizosphere microbial activity, further reinforcing aggregation. Consequently, the Technosols showed 27-51% higher water-stable aggregates, 429-528% higher mineral-associated organic carbon content, and 15-38% lower electrical conductivity. Spectroscopy and high-resolution mass spectrometry analyses revealed enhanced transformations of aromatic, oxidized, and nitrogen-rich dissolved organic matter, favoring carbon and nitrogen preservation. Microbial analysis showed enrichment of taxa related to mineral weathering, recalcitrant carbon turnover, and plant growth promotion, and these were associated with improved aggregate stabilization. These findings provide a promising way for waste resource recovery and stable Technosols formation with implications for soil utilization.