Effect of foliar-applied boron and sulphur on flowering phenology in Calendula officinalis L.

Abstract

The present investigation was carried out to evaluate the influence of foliar-applied Boron and Sulphur on the flowering phenology of Calendula officinalis L. The experiment was conducted in a factorial randomized block design with three levels of Boron (B?: 0%, B?: 0.1%, B?: 0.2%) and Sulphur (S?: 0%, S?: 0.1%, S?: 0.2%), applied as foliar sprays at the pre-flowering stage. Observations were recorded on days to first bud emergence, days to 50% flowering, and flowering duration across two consecutive seasons. The results revealed that combined foliar application of 0.2% Boron and 0.2% Sulphur (B?S?) significantly advanced bud initiation and 50% flowering, while also extending the overall flowering period compared to control (B?S?) and individual treatments. The enhancement in flowering traits may be attributed to the synergistic role of Boron in reproductive development and Sulphur in protein synthesis. These findings suggest that the integrated application of Boron and Sulphur can effectively optimize flowering behaviour in Calendula officinalis for ornamental or commercial cultivation.