Developing a nitrogen application curve for spray chrysanthemums grown in hydroponic system and its practical use in NFT system

Spray chrysanthemums 'Talk' (autumn-flowering type) were grown in a hydroponic system with N supply maintained at high levels. The plant growth, N uptake, and cut flower quality were subsequently evaluated in relation to 3 different planting dates. Fresh plant weight and N uptake increased throughout the growing period but at a decreasing rate towards harvest. Shoot lengths and weights ranged from 92~112cm and 85~97g, respectively. Comparison revealed that the cut flowers were longer and heavier than a standard of best grade in the market. Based on N uptake and plant growth, a down-regulated N application curve (NAC) was developed for producing economically marketable cut flowers. To produce a plant having two shoots of 70g, which is probably suitable for the market, 954~1142mg N fertilizer was computed to be appropriate. Using the NAC, spray chrysanthemum 'Talk' was grown in Nutrient Film Technique (NFT) system. Under 0.8 and 1.0 strengths of NAC, the mean shoot lengths and weights were ≥ 94.2 cm and ≥ 65.6g, respectively, yielding more than 64% of best grade cut flowers. At NAC 0.8 and 1.0 strengths, 90~100% N, 90~98% P and K of applied amounts were consumed, thus confirming an efficient uptake of these nutrients. Consequently, the nutrient application based on 0.8~1.0 strengths of NAC could produce economically marketable autumn-flowering spray chrysanthemums.