The present study investigates the influence of zinc nanoparticle (ZnO NPs) application on the flowering and fruiting characteristics of guava (Psidium guajava L.) cv. 'Lucknow-49' in the sub-Himalayan Terai region of West Bengal, India. The experiment was conducted during 2020–2021 at the Instructional Farm, Department of Pomology and Post-Harvest Technology, Uttar Banga Krishi Viswavidyalaya, Pundibari, Cooch Behar, utilizing guava plants spaced at 4 × 4 m. A randomized block design (RBD) with three replications was used to evaluate the comparative efficacy of ZnO NPs at concentrations of 25, 50, 75, and 100 µg mL−1: traditional Zn-EDTA (1.0%), ZnSO4 (1.0%), and a water spray, respectively. Foliar applications were applied at three critical phenological stages: 30 days before flowering, 15 days after fruit set, and 30 days following the second spray. The results demonstrated that foliar application of ZnO NP at 25 µg mL−1 significantly reduced the number of days to flower bud emergence (23.89 days). By contrast, ZnO NP at 75 µg mL−1 extended the flowering duration (44.67 days) and maximized fruit yield (10.91 kg per plant). Based on these findings, the study concluded that foliar application of ZnO NPs at 75–100 µg mL−1 enhances flowering, fruiting, and quality traits in guava cv. 'Lucknow-49' grown in the sub-Himalayan Terai region of West Bengal.
Bhowmick et al. (2025) studied this question.