Flower yield and chemical composition of essential oil from Rosa damascena under foliar application of Ca(NO3)2 and seasonal variation

Rosa damascena is an important essential oil-bearing industrial crop. Rose essential oil is extremely precious natural ingredient in aromatic, cosmetic, food, and pharmaceutical industries. However, ecology and plant nutrition play major roles in flower yield and composition of oil. The main objective was to understand the effects of seasonal variation and foliar application of Ca(NO3)2 on R. damascena under the western Himalayan conditions. Thus, a field experiment was conducted with 12 treatment combinations involving two cropping seasons (2012–2013 and 2013–2014) and six levels of Ca(NO3)2 (water spray as control, Ca(NO3)2 at 2.5, 5.0, 7.5, 10.0 and 12.5 g L−1 of water). The first cropping season produced significantly higher flower yield (1044.55 g bush−1) than the second cropping season (699.89 g bush−1). Irrespective of the cropping seasons, the foliar application of Ca(NO3)2 at 10.0 g L−1 registered significantly higher flower yield (993.56 g bush−1) compared with the controlled treatment, but remained statistically at par with 7.5 and 12.5 g L−1. Although the essential oil content in flower was not affected by both the factors, the variations were observed in chemical compositions of essential oil. Analysed data revealed that the effect of seasonal variation on compositions of essential oil was more pronounced compared to the application of Ca(NO3)2. The PCA biplots also indicated the highly positive correlations among the major hydrocarbons. Despite the significant effects of seasonal variation on the accumulations of total N and P in leaves, insignificant results were found for K and Chl. The results suggest that flower yield and compositions of oil are governed by the environmental conditions; moreover, the higher flower yield can be obtained through the foliar application of Ca(NO3)2 under rainfed conditions.