Nitrogen, phosphorus, and potassium requirements for optimizing growth and flowering of the nobile Dendrobium as a potted orchid
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Experiments were conducted to determine how nitrogen (N), phosphorus (P), and potassium (K) rate and fertilizer termination time affect the growth and flowering of a Dendrobium nobile Lindl. hybrid, Dendrobium cv Red Emperor Prince. Nitrogen, P, and K were tested in separate experiments as a factorial combination of five rates and three termination dates (1 Sept., 1 Oct., and 1 Nov. 2005). Nitrogen and K rates were 0, 50, 100, 200, and 400 mgL1. Phosphorus rates were 0, 25, 50, 100, and 200 mgL1. Levels of the nutrients not being tested were held constant. For all nutrients, ending fertilization on 1 Sept. resulted in greater or similar pseudobulb thickness compared with ending fertilization on 1 Oct. or 1 Nov. Pseudobulbs grew taller as the N rate increased, peaking at 100 and 200 mgL1. There were interactions between the N rate and fertilizer termination time on all reproductive characteristics. For all fertilizer termination times, flower number increased once N was applied. When ended on 1 Nov., 200 and 400 mgL1 N caused a delay to reach anthesis. All P rates resulted in taller plants with equally more nodes when compared with 0 mgL1. As the K rate increased from 0 to 100 mgL1, plant height increased, with no further increase at higher rates. The number of leaves remaining increased as N and K rates increased up to 200 mgL1. Total flower number and flowering node number increased as the K rate increased to 100 mgL1 (terminated on 1 Sept.) or 50 mgL1 (terminated on 1 Oct. or 1 Nov.). In the fourth experiment, only N was ended at four termination times, whereas all other nutrients continued to be supplied until flowering. Control plants received all fertilizer elements until flowering. The duration of N application did not affect vegetative or flowering characteristics. No aerial shoots were observed as a result of prolonged application of N at all rates. In summary, 100 mgL1 N, 25 mgL1 P, and 100 mgL1 K are recommended for optimal vegetative growth and reproductive development of Dendrobium cv Red Emperor Prince.
