The effect of different ratios of ammonium to nitrate and calcium levels on growth, concentration of nutrients and quality of roses

In order to study the effect of different ammonium to nitrate ratios and calcium levels on the growth, nutrient concentration and quality of rose (Rosa hybrida L.) under hydroponic conditions, this experiment was conducted as a factorial experiment in a randomized complete block design with two factors: ammonium to nitrate ratio and calcium in the nutrient solution with four replications on rose cultivar Vendetta plants for one year from 2006. The levels of the ammonium to nitrate ratio factor included three levels: 0:100, 25:75 and 50:50, and the levels of the calcium factor included two levels: 1.6 and 4.8 mM. The results showed that, except for the leaf chlorophyll index, none of the vegetative growth indices were affected by different ammonium to nitrate ratios and applied calcium levels. With increasing ammonium to nitrate ratio in the nutrient solution, the concentrations of nitrogen, phosphorus and trace elements in different parts of rose increased, and calcium and magnesium decreased. While increasing the calcium concentration in the nutrient solution had no effect on the concentrations of nitrogen, phosphorus, iron, copper and boron in different parts of rose, it led to a significant increase in calcium concentration and also a significant decrease in the concentrations of potassium, magnesium, manganese and zinc in different parts of rose. In both harvests, increasing the ammonium to nitrate ratio in the nutrient solution resulted in a significant increase in rose yield, although no significant difference was observed between the 25:75 and 50:50 ammonium to nitrate ratios. A study of flower quality indices in the postharvest period showed that by increasing the ammonium to nitrate ratio in the nutrient solution to a ratio of 50:50, the fresh weight of the flowering stem at the end of shelf life, the final flower diameter, and shelf life were significantly reduced. While increasing the calcium concentration in the nutrient solution to 4.8 mM led to an increase in all of the above indices compared to the 1.6 mM level. Based on the results of this research, from the point of view of economic production and quality indicators of roses in the post-harvest stage, the application of 25% of the total nitrogen consumed in the form of ammonium and also 4.8 mM calcium is recommended for the production of roses in hydroponic conditions.