Efficacy of humic acid and seaweed extracts on growth, yield and biochemical properties of Chili

Chilli is a significant horticultural crop in Bangladesh, contributing to spice production and the rural economy. This investigation aimed to evaluate the effect of humic acid and seaweed extracts as bio-stimulants on plant growth, yield, and biochemical properties of chilli (var. Hira 1701 Supreme). There were four treatments in this research: T0 (control), T1 (recommended fertilizer + humic acid), T2 (recommended fertilizer + seaweed extract), and T3 (recommended fertilizer + both seaweed extract and humic acid). The results indicated that T2 possessed the highest values in the most studied parameters, including plant height (60.13 cm), number of leaves (98.75), number of branches (13.25), number of flowers (37.63), fruit length (7.92 cm), seeds per fruit (79.75), yield per plot (1156.5 g), yield per hectare (7.23 ton), plant fresh weight (187.50 g⁻¹ Plant), plant dry weight (41.00 g⁻¹ Plant), vitamin C (177.80 mg 100 g⁻¹ FW), total phenolic content (164.87 mg 100 g⁻¹ FW), total flavonoid content (35.95 mg 100 g⁻¹ FW), crude protein content (8.63%), and total soluble solids content (5.80 °Brix). While T1 and T3 also performed better than the control (T0), T2 consistently outperformed all other treatments. Correlation analysis revealed strong positive associations among yield, plant physiology, and key biochemical traits, indicating their interdependence. Moreover, PCA-based biplot analysis clearly separated the treatments and confirmed that T2 showed a strong correlation with enhanced agronomic performance and superior nutritional quality. These findings show that seaweed extract foliar spray with the recommended fertilizer is superior to humic acid alone for enhancing chilli growth, productivity,