Development of a Fire-Resilient Soil Amendment for Enhancing Post-Wildfire Soil Recovery, Nutrient Retention, and Plant Growth

Wildfires are increasingly frequent and severe disturbances that can degrade soil structure, alter hydrological behaviour, modify nutrient availability, and delay vegetation recovery. This study investigated the effects of controlled thermal exposure on the physical, chemical, and biological properties of four contrasting soil materials—clay, sand, peat moss, and vermiculite—with loamy soil used as a reference. Hydraulic behaviour was assessed using drainage time, filtrate volume, and calculated water retention. Changes in pH and the qualitative availability of nitrogen (N), phosphorus (P), and potassium (K) were evaluated using soil-testing kits. Green gram (Vigna radiata) was used as a biological indicator of post-fire plant establishment. Based on the comparative performance of individual components, two composite formulations were developed. Solution 2, comprising 30% clay, 30% vermiculite, 25% sand, and 15% peat moss, demonstrated the most favourable overall performance, particularly in plant growth and nutrient retention after thermal exposure, whereas Solution 1 showed slightly better hydrological performance. These findings indicate that combining soil components with complementary water-management, nutrient-retention, and biological properties may improve post-wildfire soil resilience. The proposed formulation represents a laboratory-scale proof of concept for post-fire restoration; field validation and quantitative chemical and physical characterization are required before practical deployment.