Elucidating the Molecular Mechanisms and Comprehensive Effects of Sludge‐Derived Plant Biostimulants on Crop Growth: Insights from Metabolomic Analysis

Abstract The utilization of urban waste for land management plays a crucial role in reshaping material flows between human activities and the environment. Sewage sludge alkaline thermal hydrolysis (ATH) produces sludge‐derived plant biostimulants (SPB), which have garnered attention due to the presence of indole‐3‐acetic acid. However, there remains a gap in understanding SPB's molecular‐level effects and its comprehensive impact on crops throughout their growth cycle. In this study, non‐targeted and targeted metabolomic approaches are employed to analyze 51 plant hormones and 1,177 metabolites, revealing novel insights. The findings demonstrate that low concentrations of SPB exerted multiple beneficial effects on rice roots, leaves, and the root‐soil system, facilitating rapid cell division and enhancing antioxidant defense mechanisms. These results provide a vital foundation for understanding ATH metabolic pathways and advocating for widespread SPB application, offering significant implications for sustainable land management.