This study shows how combining three natural substances—rice husk biochar (a carbon-rich soil additive), Cassia fistula plant extract, and a beneficial fungus called Trichoderma harzianum—can effectively protect chickpea crops from a harmful soil disease called collar rot. The combination not only reduced disease occurrence from 64% to 35% but also improved plant growth and strengthened plants’ natural defense mechanisms. This eco-friendly approach offers farmers a sustainable alternative to chemical fungicides while improving soil health and crop productivity.