Influence of fertilization and a high daily light integral on the growth and flowering of Phalaenopsis

Phalaenopsis growers are continuously trying to grow high quality crops with a shorter crop cycle. To this end growers are using a much higher daily light integral (DLI). It was hypothesized that in order to increase the DLI by a factor 1.5-2 and maintain a balance of resources for the plant, it is necessary to increase the mineral concentration in the nutrient solution. To this end a crop of six Phalaenopsis cultivars were grown at a DLI of 8-10 mol/m·d and 3 nitrogen concentrations (14, 20 and 26 mM), all at 2 EC levels (1.0 and 1.7 mS/cm), 6 treatments in total. The above ground biomass increased with increasing EC and nitrogen. The proportion of plants with 2 or more spikes decreased with increasing nitrogen at the cost of plants with 1 spike. Approximately 15% of the plants produced more than 2 spikes, irrelevant of the EC. Likely due to some nutritional imbalance, a number of the developing spikes became diseased with Fusarium solani, especially at 26 mM nitrogen in the nutrient solution. High levels of nitrogen initially had a positive effect on the growth of Phalaenopsis, but a more dynamic fertilization schedule, lowering the nitrogen concentration in the later developmental stages of Phalaenopsis, might be advisable. Based on the results of this trial with these cultivars, a nutrient solution with an EC 1.0 and 14 or 20 mM nitrogen appears to be the best choice. In this treatment, the highest number of spikes, virtually no problems with spike disease, and a good number of newly formed leaves with potential for flowering spikes was observed.