Effects of different concentrations of Nitrogen and Potassium on morpho-physiological indices of ornamental kale

Ornamental Kales are one of the most important plants of the autumn season, they are the only ornamental plants in the green space in the cold season due to their tolerance to cold and frost. Nutrition and temperature are important factors affecting plant quality, especially in terms of plant height, canopy size and color, and leaf size and number. An experiment was conducted to investigate the interaction effect of different concentrations of nitrogen and potassium fertilizers on morpho-physiological indices of ornamental kale. The treatments include the interaction of concentrations of 125, 175 and 225 mg L-1 of nitrogen and potassium (from the source of urea and potassium sulfate, K2SO4) in the form of N:K ratios including 125:125, 125:175, 125:225, 175:125, 175:175, 175:225, 225:125, 2 25:175 and 225:225 and distilled water (as control). The results showed that the treatments had a significant effect on all the measured indices. The highest fresh and dry weight of the shoot was belonged to N:K treatment equal to 175:175. The highest number of leaves in the 125:125 treatment, the highest crown diameter in the 225:225 treatment, and the highest leaf chlorophyll content was belonged to 175 mg L-1 nitrogen along with different concentrations of potassium. The highest soluble sugar was observed in the treatments containing 175 and 225 mg L-1 of nitrogen and potassium, and the highest proline was observed in the 225:225 treatment. The highest amount of anthocyanin was belonged to the control and among the fertilization treatments, it was belonged to the level of 125 mg L-1 of potassium. Based on these observations and also considering the importance of canopy diameter in ornamental kale, the amount of 175 to 225 mg L-1 of nitrogen along with 225 mg L-1 of potassium can be suggested for the optimal growth of this plant.