Masters Degrees (Agronomy)

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Browsing Masters Degrees (Agronomy) by browse.metadata.advisor "Hoffman, L. (Lynn) (Horticulturalist)"

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    Cultivation aspects of hydroponic cut tulip (Tulipa gesneriana) production in South Africa
    (Stellenbosch : Stellenbosch University, 2013-12) Derbyshire, Geline; Kempen, Estelle; Hoffman, L. (Lynn) (Horticulturalist); Stellenbosch University. Faculty of AgriSciences. Dept. of Agronomy.
    ENGLISH ABSTRACT: Tulip cut flowers are considered speciality flowers, but are cultivated on a limited scale in South Africa. Published research done on the cultivation aspects of Tulipa spp. in warm climates is sparse and insufficient. The production potential of this valued floriculture crop under South African conditions however prompts a need for research as profitable returns can only be realised when cut tulip producers deliver high quality tulips, both for the local and potentially the export market. Understanding how cut tulips react to different cultivation aspects under local conditions is key in developing successful and profitable forcing programs for cut tulip production in South Africa. In order to produce quality tulips it is vital that producers minimize the occurrence of physiological disorders by optimizing cultivation aspects such as nutrition, bulb quality and age, cultivar selection as well as postharvest treatments. To study the nutritional requirements of cut tulips produced in a hydroponic system under South African conditions two similar experiments were conducted, using early-forcing and late-forcing tulip bulbs respectively. In each experiment the effect of four different nutrient solution formulations (“Current SA”, “Standard Steiner”, “Europe”, “Europe+NH4”) and four different cut tulips cultivars (‘Leen van der Mark’, ‘Jan van Nes’, ‘Ill de France’, ‘Royal Virgin’) on growth, quality and vase life was evaluated. Results showed that although nutrient solutions did not significantly affect the scape growth of cut tulips, vase life was significantly affected by nutrient solution formulation for both early- and late-forcing bulbs. For early-forcing bulbs nutrient solution “Europe” produced tulips with a significantly longer vase life than other nutrient solutions and for late-forcing bulbs nutrient solution “Standard Steiner” produced tulips with a significantly longer vase life than other nutrient solutions. Cultivars differed significantly in terms of growth, quality and vase life for both early- and late-forcing bulbs. It was found that the cultivar ‘Leen van der Mark’ presented the longest stem length, greatest fresh weight and longest vase life of all cultivars evaluated for both early- and late-forcing bulbs and it seems to be a cultivar with a low risk in terms of quality and vase life for forcing hydroponically in warm climates. As stem topple, a physiological disorder which can be prevalent in hydroponically produced tulips, has been shown to be reduced by the application of calcium fertilizers, the next experiment was conducted to investigate the role of foliar sprays to reduce or eliminate this common disorder. Various foliar spray treatments, including calcium nitrate (CaNO3), CalTrain, NonTox Silica® and an untreated control, were evaluated for their effect on the occurrence of postharvest stem topple and the vase life of the two tulip cultivars ‘Jumbo Pink’ and ‘Strong Gold’ respectively. Trends indicated that foliar sprays containing calcium, “CaNO3” and “CalTrain”, reduced the incidence of postharvest stem topple. The vase life of hydroponically forced cut tulips was significantly increased by the use of foliar fertilizer sprays as compared to the control. The vase life of cut tulips is an important parameter directly affecting quality. In a final experiment, the efficacy of three postharvest treatments to extend the vase life and minimize postharvest stem elongation of the four cut tulip cultivars ‘Deshima’, ‘Synaeda Orange’, ‘White Marvel’ and ‘Margarita’ was evaluated. Treatments consisted of an untreated control, an overnight stem pulse of Chrysal BVBPlus, a four hour fumigation of Chrysal Ethylene Buster® (1-MCP) and a combination of the latter treatments. Vase life, postharvest stem elongation and vase-solution used were parameters measured. No statistically significant effects on any parameters measured could be identified between the various treatments. Trends observed suggest that treatments containing BVBPlus may prolong the vase life, minimize postharvest stem elongation and improve the usage of vase life solution of hydroponically produced cut tulips. BVBPlus thus shows potential for use as an essential postharvest treatment for cut tulips produced hydroponically under warm climate conditions, but further research is needed for conformation. This research is a first report on key agronomical aspects of the hydroponic cultivation of cut tulips in South Africa and aims to serve as a basis for future research, ultimately to support successful commercial cultivation of tulips on a larger scale in South Africa as well as internationally.