To prepare Fertilizer A, 50 g of the homogenized plant residue was placed in a 250 mL beaker. Subsequently, 25 mL of 50% Nitric acid was added, and the mixture was heated at 120°C for 20 minutes. After cooling to 60°C, 10 g of wood ash was added while stirring for 10 minutes. The mixture was then transferred to an aluminum foil and oven-dried at 80°C for 24 hours, as illustrated in Figure .