Determining the nutritional requirements for optimizing flowering of the nobile dendrobium as a potted orchid
Bichsel, Rebecca Gayle
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Five experiments were conducted to determine how nitrogen (N), phosphorus (P), and potassium (K) rate and fertilizer termination time, duration of N application, and cold duration and light intensity affect growth and flowering of Dendrobium nobile Red Emperor ?Prince?. The N, P, and K experiments were a factorial combination of five nutrient rates and three termination dates (1 Sept., 1 Oct., and 1 Nov. 2005). N and K rates were 0, 50, 100, 200, and 400 mg?L-1. Phosphorus rates were 0, 25, 50, 100, and 200 mg?L-1. For all nutrients, terminating fertilization on 1 Oct. or 1 Nov. resulted in thinner pseudobulbs. Pseudobulbs grew taller as N rate increased, peaking at 100 and 200 mg?L-1. There were interactions between N rate and fertilizer termination time on all reproductive characteristics. For all fertilizer termination times, flower number increased once N was applied. When terminated on 1 Nov., 200 and 400 mg?L-1 N caused a delay for the first flower to reach anthesis. Plants required more days to full flower when supplied with 200 mg?L-1 N until 1 Oct. All P rates resulted in taller plants with equally more nodes compared to 0 mg?L-1. For all three termination times, plants that were not supplied with P bloomed later than those receiving P. Plants produced the most flowers when P fertilization was terminated on 1 Oct. Plants required fewer days to reach full flower at the 1 Sept. P termination time. As K rate increased from 0 to 100 mg?L-1, height increased, with no further increase at higher rates. Total flower number and flowering node number were the lowest at 0 mg?L-1 K. Leaf number increased as N and K rates increased up to 200 mg?L-1. Nitrogen application did not affect vegetative or flowering characteristics when one rate was applied at four termination dates. In the last experiment, plants cooled at 10 ?C for 2, 4, or 6 weeks with light or 4 weeks in darkness produced similar higher number of flowers per plant than those cooled in darkness for 2 or 4 weeks or those that remained in a greenhouse.