Effects of Nanocarbon-Fortified Fish Hydrolysate on the Morphophysiological Responses of Chilli (Capsicum annuum L.) under Drought Stress

Chilli (Capsicum annuum L.) is an economically important seasonal spice crop, and its productivity and harvest quality are highly constrained by drought stress under many cultivation conditions. This study aimed to evaluate the effectiveness of nanocarbon-enriched fish hydrolysate in enhancing drought tolerance in chilli plants. The MI2 chilli variety was cultivated in pots using a Randomized Complete Block Design with seven treatments and six replicates per treatment. Treatments included a commercial Albert nutrient solution (positive control I), an inorganic solid fertilizer (positive control II), fish hydrolysate alone at 2.5% (v/v), and enriched with carbon nanoparticles at concentrations of 25, 50, and 75 mg/L, and water as a negative control. Following transplanting, four foliar spray applications were applied at five-day intervals. After the fertilization phase, drought stress was imposed by withholding irrigation for seven consecutive days. Growth parameters, including plant height, leaf area, root length, root volume, and root dry weight, and physiological parameters such as chlorophyll content and leaf relative water content were recorded. Although positive control I exhibited the highest plant height (16.42 cm) and leaf area (10.92 cm2), nanocarbon-enriched fish hydrolysate treatments at 50 mg/L and 75 mg/L displayed higher root length, root volume, root dry weight, chlorophyll content, and relative water content compared to both positive controls and fish hydrolysate alone, demonstrating that nanocarbon incorporation improves the efficacy of fish hydrolysate. Therefore, nanocarbon-enriched fish hydrolysate could be recommended as a cost-effective, environmentally friendly, and sustainable strategy under limited water availability in chilli cultivation.