Cultivation aspects of hydroponic cut tulip (Tulipa gesneriana) production in South Africa

Derbyshire, Geline (2013-12)

Thesis (MScAgric)--Stellenbosch University, 2013.

Thesis

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.

AFRIKAANSE OPSOMMING: Tulp snyblomme word beskou as spesialiteitsblomme, maar word op 'n beperkte skaal in Suid-Afrika verbou. Gepubliseerde navorsing gedoen oor die verbouingsaspekte van Tulipa spp. in warm klimate is skraps en onvoldoende. Die potensiële belangrikheid van kennis aangaande verbouingsaspekte van hierdie gewas in warm klimate toon 'n behoefte aan navorsing onder plaaslike Suid-Afrikaanse toestande, aangesien winsgewende opbrengste slegs verwesenlik kan word wanneer sny tulp produsente ‘n hoë kwaliteit produk lewer aan beide die plaaslike en moontlik ook die uitvoermark. Die begrip van hoe hierdie gewas reageer op verskillende aspekte van verbouing onder plaaslike toestande is noodsaaklik vir suksesvolle en winsgewende sny-tulp produksie in Suid-Afrika. Om hoë kwaliteit tulpe te produseer, is dit van kritiese belang dat produsente die voorkoms van fisiologiese afwykings minimaliseer deur die optimalisering van verbouingsaspekte soos voeding, bolgehalte en ouderdom, kultivar keuse, sowel as na-oes behandelings. Om die voedingsbehoeftes te bestudeer van sny tulpe wat in hidroponiese stelsels onder Suid-Afrikaanse toestande gekweek word, was twee soortgelyke eksperimente uitgevoer, met behulp van vroeë-geforseerde en laat-geforseerde tulp bolle onderskeidelik. In elke eksperiment was die effek van vier voedingsopslossings (“Current SA”, “Standard Steiner”, “Europe”, “Europe+NH4”) en vier sny tulp kultivars (‘Leen van der Mark’, ‘Jan van Nes’, ‘Ill de France’, ‘Royal Virgin’) op groei, gehalte en vaaslewe geëvalueer. Resultate bevind het getoon dat hoewel voedingsoplossing formulasie geen beduidende effek op steel groei gehad het nie, was vaaslewe beduidend geaffekteer deur voedingsoplossing formulasie vir beide vroeë- en laat-geforseerde bolle. Vir vroeë-geforseerde bolle het die voedingsoplossing “Europe” tulpe produseer met ‘n beduidende langer vaaslewe as die ander voedingsoplossings en vir laat-geforseerde bolle het die voedingsoplossing “Standard Steiner” tulpe produseer met ‘n beduidende langer vaaslewe as die ander voedingsoplossings. Kultivars het beduidend verskil in terme van groei, kwaliteit en vaaslewe vir beide vroeë- en laat-geforseerde bolle. Daar was bevind dat die kultivar ‘Leen van der Mark’ die langste steel lengte, hoogste vars massa en die langste vaas lewe van al die kultivars vir beide vroeë- en laat-geforseerde bolle getoon het. ‘Leen van der Mark’ blyk ‘n kultivar te wees met ‘n lae risiko in terme van kwaliteit en vaas lewe asook geskik vir hidroponiese forsering onder warm klimaatstoestande. Aangesien die vermindering van steelkantel, ‘n fisiologiese afwyking wat heersend kan voorkom in hidroponiese gekweekte tulpe, bewys is deur die aanwending van kalsium bemesting, is ‘n volgende eksperiment onderneem om die rol van verskeie blaarbespuitings te evalueer om hierdie fisiologiese afwyking te verminder of te voorkom. Verskeie blaarbespuiting behandelings, insluitend kalsium nitraat (CaNO3), CalTrain, NonTox Silica® en 'n onbehandelde kontrole, is geëvalueer vir hul effek op die voorkoms van na-oes steelkantel en die vaas lewe van die twee tulp kultivars 'Jumbo Pink’ en ‘Strong Gold' onderskeidelik. Tendense het aangedui dat die kalsium-bevatttende blaarbespuitings , "CaNO3" en "CalTrain" wel die voorkoms van die na-oes steel kantel kon verminder. Die vaas lewe van hidroponies geforseerde sny tulpe is betekenisvol verhoog deur die gebruik van blaarbespuitings kunsmis soos in vergelyking met die kontrole. Die vaas lewe van sny tulpe is 'n belangrike parameter wat direk gehalte affekteer. In 'n laaste eksperiment, is die doeltreffendheid van drie na-oes behandelings geëvalueer om die vaas lewe van die vier sny tulp kultivars ‘Deshima', ‘Synaeda Orange', 'White Marvel' en 'Margarita' te verleng. Behandelings het bestaan uit 'n onbehandelde kontrole, 'n oornag steel puls van Chrysal BVBPlus, 'n vier uur beroking met Chrysal Ethylene Buster ® (1-MCP) en 'n kombinasie van die laaste behandelings. Vaas lewe, na-oes stamverlenging en vaas-oplossing verbruik, was parameters wat gemeet was. Geen statisties beduidende uitwerkings op enige parameters gemeet was geïdentifiseer tussen die onderskeie behandelings nie. Tendense waargeneem dui egter daarop aan dat behandelings wat BVBPlus bevat die vaas lewe kan verleng, na-oes stamverlenging verminder en die gebruik van vaas oplossing verbeter in sny tulpe wat hidroponies geproduseer is in ‘n warm klimaat. BVBPlus toon dus potensiaal as 'n noodsaaklike na-oes behandeling vir sny tulpe wat hidroponies gekweek is onder warm klimaatstoestande, maar verdere navorsing is nodig om dit te bevestig. Hierdie navorsing is 'n eerste verslaggewing oor belangrike agronomiese aspekte van die hidroponiese verbouing van sny tulpe in Suid-Afrika en het ten doel om te dien as 'n basis vir toekomstige navorsing, met die uiteindelike doel om die kommersiële suksesvolle verbouing van tulpe te ondersteun op 'n groter skaal in Suid-Afrika sowel as internasionaal.

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