Witloof chicory (Cichorium intybus L. var.foliosum) - evaluation of new forcing techniques.

Konig, Roman (2002-03)

Thesis (DPhilAgric)--Stellenbosch University, 2002

Thesis

ENGLISH ABSTRACT: South Africa is one of the worlds leading producers of chicory (Cichorium intybus L.). Most of the chicory produced is used locally for the production of instant coffee. Witloof chicory, or Belgian endive, however, is a vegetable crop grown from the root of Cichorium intybus L. var. foliosum. This is done by placing the mature taproot in a controlled, dark environment after vernalization and supplying it with water and nutrients by means of hydroponics. Witloof chicory is new to the South African market and is only produced on a limited scale. Nonetheless, seeing that chicory is successfully grown on a large scale for the coffee industry it seemed reasonable to investigate the cultivation of this essentially unknown vegetable locally. The focus of this study was on the evaluation of new witloof production techniques during the second stage of witloof (chicon) cultivation, also called 'forcing'. To this end, locally grown witloof chicory roots were used in all trials. In order to establish the effects of several irrigation methods on lateral root formation and chicon quality, witloof chicory roots were forced using the conventional means of hydroponic irrigation as well as ebb-and-flood and aeroponic irrigation. Lateral root formation was significantly increased when either ebb-and-flood or aeroponic irrigation was applied compared to that obtained with the conventional method. This increase in lateral root formation was, however, to the detriment of chicon quality (QI), possibly as a result of competition for limited carbohydrate reserves. In an attempt to optimize the aeroponic irrigation method, roots were forced in non-vertical positions. Placing roots horizontally during forcing resulted in a significantly lower marketable chicon yield than where roots were placed vertically. The loss in yield was probably brought about by an increased fallout percentage rather than by a decrease in chicon production. Considering the pivotal role that sucrose plays in the development of the chicory head, sucrose was applied exogenously to the root before and/or during forcing. Dry matter chicon yield was negatively effected by exogenously applied sucrose. This could have been due to an increased incidence of fungal or bacterial infections or causative of roots absorbing less water resulting in the inability of the plant to utilize the applied sucrose during chicon development. Fungal and bacterial infections are known to have a detrimental effect on witloof chicory production. An environmentally friendly product for disease control, 'Desogerme SP®', was used to contain or reduce infection. Irrigation of roots with 'Desogerme SP®' containing nutrient solution increased chicon yield by 31%. From this study it became clear that some new production techniques applied had the potential of improving lateral root formation or quality during growth. However, the conventional way of irrigation remains the most effective compared to the other techniques applied, but could possibly be improved to some extent by incorporating 'Desogerme SP®' either as a pretreatment or in the nutrient solution. A breakthrough was made with the development of the quality index (QI). The ongoing limitation of statistically analyzing quality data of chicons sorted according to quality-classes was overcome by making use of this tool. Despite the fact that the index was developed specifically for use on witloof, it is has the potential of being applied to quality data of a wide variety of crops.

AFRIKAANSE OPSOMMING: Suid Afrika is een van die wêreld se grootste produsente van sigorei (Cichorium intybus L.). Die meeste plaaslik geproduseerde sigorei word vir die produksie van kitskoffie benut. Witloofsigorei, of Belgiese "endive", is egter 'n groentegewas wat vanaf die wortel van Cichorium intybus L. var. foliosum gekweek word. Dit word gedoen deur die volwasse penwortel na vemalisasie in 'n gekontroleerde, donker omgewing te plaas en met 'n hidrokultuurstelsel van water en voedingselemente te voorsien. Witloof is nuut op die Suid Afrikanse mark en word net op beperkte skaal geproduseer. Aangesien sigorei suksesvolop groot skaal vir die koffieindustrie geproduseer word, blyk dit logies om die moontlikhede te ondersoek om hierdie relatief onbekende groente plaaslik te kweek. Die fokus van hierdie studie was gerig op die evaluasie van nuwe produksietegnieke gedurende die tweede fase van witloofproduksie, wat ook as forsering bekend is. Plaaslik gekweekte witloof sigoreiwortels is vir alle eksperimente gebruik. Die invloed van 'n verskeidenheid besproeiingsmetodes is op sywortelproduksie en witloof krop-kwaliteit ondersoek. Witloofwortels is geforseer deur van 'n konvensionele hidrokultuur-stelsel gebruik te maak wat met 'n ebb-en-vloed en 'n lugsproei sisteem vergelyk is. Sywortel-produksie was betekenisvol hoër waar ebb-en-vloed of lugsproei sisteme toegepas is. Hierdie verbetering in sywortel-ontwikkeling was egter tot nadeel van krop-kwaliteit, vermoedelik as gevolg van die allokasie van koolhidrate na sywortels, eerder as na die groeipunt. In 'n poging om die lugsproei besproeiingsmetode te verbeter en om swamsiektes te verminder, is wortels in nie-vertikale posisies geforseer. Wortels wat gedurende forsering horisontaal ingetafel was, het 'n betekenisvol laer opbrengs van bemarkbare kroppe getoon as wortels wat vertikaal geplaas was. Die verlies aan opbrengs kon toegeskryf word aan 'n verhoging van afval, aangesien geen betekenisvolle afname in vars krop-gewig gevind is nie. Aangesien sukrose 'n belangrike rol in die ontwikkeling van die witloofkrop speel, is sukrose voor en tydens forsering aan die wortels toegedien. Droë materiaal krop-opbrengs is negatief deur die toediening van sukrose beïnvloed. Dit kon moontlik as gevolg van 'n verhoogde voorkoms van swam- of bakteriese infeksies gewees het of 'n aanduiding wees dat behandelde wortels minder water geabsorbeer het en die toegediende sukrose nie kon gebruik gedurende krop-ontwikkeling me. Swam- en bakteriese infeksies is bekend vir hul negatiewe uitwerking op witloofproduksie. 'n Omgewingsvriendelike middel, 'Desogerme SP®' is gebruik om siektes te beheer ofte verminder. Wortels wat met 'n 'Desogerme SP®' bevattende voedingsoplossing besproei is, het 'n 31% verhoging in krop-opbrengs getoon. Uit data wat gedurende hierdie studie ingesamel is, blyk dit duidelik dat sommige van die nuwe produksietegnieke wel die potensiaal het om sekere planteienskappe te verbeter. In geheel gesien bly die konvensionele metode van besproeiing die mees effektiewe, wanneer dit vergelyk word met die ander wat getoets is. Die konvensionele metode kan moontlik verbeter word as 'Desogerme SP®' as 'n vooraf-behandeling of as deel van die voedingsoplossing geïnkorporeer word. 'n Deurbraak is met die ontwikkeling van 'n kwaliteitsindeks (QI) gemaak. Ernstige beperkings word met statistiese ontledings van kwaliteitsdata ervaar waar kroppe volgens kwaliteitskiasse gesorteer word. Hierdie probleme is met behulp van die QI oorkom. Ongeag die feit dat die indeks spesifiek vir gebruik by witloof ontwikkel is, het dit die potensiaal om toepassing te vind by 'n wye reeks landboukundige produkte.

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