Efficacy of Various Nutrition Regimes on Growth, Flowering, and Seed Yield of Calendula officinalis

Effects of fertilization with N, P, or K alone or in various combinations were studied on production performance and seed yield of calendula (Calendula officinalis), a popular bedding plant used extensively in Pakistan. Plants fertilized with NPK or with treatments containing N had vigorous growth due to greater plant height, higher number of leaves and lateral branches per plant, greater stem and plant diameter, and higher leaf chlorophyll contents. Plants supplied with N alone or along with P or K produced earliest flowering and had greater number of flowers and seed yield/plant. Fertilization had no effect on flower diameter or fresh or dry weight of flowers. In a second study, different levels of NPK were tested to optimize calendula production. Application of 20:10:10 or 10:20:10 g·m^-2 NPK resulted in vigorous plant growth with highest plant height and diameter; number of leaves, lateral branches and flowers; earliest flowering; and highest seed yield. Higher concentration of N at 20 g m^-2 along with 10 g·m^-2 each of P and K produced higher leaf chlorophyll contents than 10:10:10 or 20:20:20 g·m^-2 NPK. However, the different NPK levels produced similar flower and stem diameter. Results demonstrated that nitrogen is vital for quality calendula flower and seed production and growers may use 20:10:10 g·m^-2 NPK for optimal flower and seed yield of calendula.