Gibberellic Acid Application to Enhance Seed Yield and Quality in Kenaf

What is it about?

Kenaf (H. cannabinus L.) is an economically important bast fibre crop whose seed production is often constrained by poor flowering, pod set and inconsistent seed quality under late-season cultivation in Bangladesh. This study aimed to evaluate the effect of foliar gibberellic acid (GA3) applications on growth, yield and seed quality of two improved varieties (BJRI Kenaf 4 and BJRI Kenaf 5) under a standardized top-cutting regime. A two-factor factorial field experiment was conducted in a randomized complete block design with three replications during the kharif-late season. Treatments comprised five GA3 concentrations (25, 50, 75, 100 and 125 ppm) with an untreated control (0), applied twice at 7 and 14 days after top-cutting (30 DAT).

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Why is it important?

Results indicated significant varietal, GA3 and interaction effects on plant growth, reproductive traits and seed quality. Plant height increased progressively up to 75 ppm GA3 (224–226 cm) before declining at higher concentrations. Branch number per plant peaked at 75–100 ppm (8.0–8.2 branches), with similar trends observed for pods per plant (50–52 pods), seeds per pod (28–29) and thousand-seed weight (32–32.5 g). Seed yield was maximized at 75 ppm GA3, reaching 1450–1470 kg ha-¹, representing a 70% increase over the untreated control. Seed quality attributes improved with GA3, with germination percentage (96–97%) and vigor index (≈2050) peaking at 100 ppm, while electrical conductivity of seed leachates was lowest at 75 ppm, indicating superior membrane integrity. Correlation analysis revealed strong positive associations between seed yield and plant height (r = 0.87), thousand-seed weight (r = 0.82), and vigor index (r = 0.76), highlighting their utility as selection criteria for yield improvement. Overall, moderate GA3 concentrations (50–75 ppm) were most effective for enhancing seed yield and quality in kenaf under top-topping management.

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