Characterization and Evaluation of Biomass Waste Biochar for Turfgrass Growing Medium Enhancement in a Pot Experiment

The sustainable management of urban grasslands is crucial for resilient city ecosystems. With increasing urbanization, improving soil quality to support turfgrass growth has become a priority. This study evaluates biochar produced from Paulownia leaves (PLB), a low-cost byproduct of Paulownia cultivation, as a growing medium amendment. Raw leaves (PL) and PLB were characterized by SEM, FTIR, and elemental analysis to assess physicochemical changes. A three-month pot experiment under outdoor conditions was conducted with turfgrass plots exposed to different irrigation and fertilization regimes. Growing medium pH, moisture, electrical conductivity, cation exchange capacity, nutrient availability, grass chlorophyll content, and uptake were monitored. The application of PLB improved the growing medium structure, raised the pH by up to one unit, and enhanced pigment accumulation in turfgrass samples. When combined with nitrogen fertilizer, PLB significantly increased turfgrass visual quality, whereas under limited irrigation, PLB alone improved seedling establishment compared to controls. Statistical analysis confirmed significant treatment effects by ANOVA, and PCA provided a precise classification of treatment groups. These findings indicate that PLB can improve nutrient efficiency, turfgrass resilience, and organic waste management.