Influence of Different NH4+/NO3- Ratios and Calcium Levels on Growth, Nutrients Concentration, and Quality of Rose Flower

This experiment was conducted to assess the effects of different NH4+/NO3- ratios and calcium levels on growth, nutrients concentration and quality of rose flower (Rosa hybrida L.(. Statistical design was factorial in a randomized complete block with four replications. Rose plants cultivar Vandentta were grown with three NH4+/NO3- ratios (0/100, 25/75 and 50/50) in combination with two levels of calcium (1.6 and 4.8 mM) under hydroponic conditions. The results revealed that, except for leaf chlorophyll content index, none of the vegetative growth indices were affected by NH4+/NO3- ratios and calcium levels in the nutrient solution. Application of ammonium in the nutrient solution resulted in increasing N, P and micronutrients and decreasing Ca and Mg in different parts of rose flower, respectively. Also, N, P, Fe, Cu and B in the different parts of rose flower were not affected by increasing the Ca concentration in the nutrient solution. However, application of Ca resulted in increasing Ca and decreasing K, Mg, Mn and Zn in the different rose parts, respectively. At the two flower harvesting dates, yield increased significantly by application of NH4+. Also there was no difference between NH4+/NO3- ratios of 25/75 and 50/50 in the yield. However, rose quality indices during post harvest were affected significantly (P≤0.01) by the previous application of ammonium and calcium. Increasing NH4+/NO3- ratio up to 50/50 significantly reduced the weight of flowering stem at the end of vase life, as well as the flower diameter and also vase life; whereas, calcium application up to 4.8 mM significantly increased all these quality indices. On the basis of this experiment, in view of the economic and flower quality indices, the application of 25 percent of nitrogen as NH4+ and increasing level of calcium in the nutrient solution up to 4.8 mM are recommended for cut rose production in hydroponic conditions.