Fertilizer Requirement of Phalaenopsis During Reproductive Stages

In order to understand the effects of different concentrations of nitrogen, phosphorus, and potassium on flower quality and vegetative growth of Phalaenopsis amabilis, we treated mature plants with different nutrient solutions for two flowering cycles. During the first flowering cycle, flowering and flower quality were not affected by fertilization treatments; however, total leaf areas and number of new leaves were increased as the concentrations of nitrogen (0, 7.1, 14.3, 21.6 mM) and potassium (0, 2.1, 4.2, 6.4 mM) increased. Phosphorus concentration at 2.1 mM decreased shoot weight and increased leaf abscission. Increasing potassium from 0 mM to 6.4 mM increased fresh and dry weight of plants. Applying 0 mM nitrogen resulted in highest percentage of plants with leaf abscission. When nitrogen and potassium concentrations increased, leaf abscission decreased. During the second flowering cycle, days to spiking, days from spiking to bud visible, and days from spiking to first flowering were not affected by different concentrations of nitrogen, phosphorus, or potassium. The concentration of phosphorus had no effect on flower diameter and size. There was a positive relationship between the concentration of potassium and stalk diameter or number of flowers, although there were no differences between the treatments of 4.2 and 6.4 mM potassium. Increasing nitrogen concentration increased total fresh weight, total dry weight, total leaf areas and number of newly formed leaves. Less effects were found on the quality of flower and growth of Phal. amabilis by applying different concentrations of phosphorus, compared with those of nitrogen and potassium. In this study, nutrient solution with 14.3 mM nitrogen, 1.4 mM phosphorus and 6.4 mM potassium resulted in best flower quality and vegetative growth in Phal. amabilis.