Thesis (MScAgric)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: The potential importance of soilless production, particularly in tomatoes, in an increasingly
water scarce South Africa prompts a need for research under local conditions. In soilless
production systems the application and availability of nutrients is closely linked to that of
water, necessitating the research of methods to increase water and fertiliser use efficiency in
soilless production systems, while diminishing environmental pollution and maintaining, or
ultimately improving, tomato yield and quality. Poor management of hydroponic fertigation
water results in pollution, and wastes precious water and expensive fertiliser. Pruning is an
important cultural practise for ensuring high productivity of hydroponic tomatoes. Adapting
pruning practises to climatic conditions could be a cheap and effective manner to improve
productivity without increasing inputs. Improving water and fertiliser use efficiency is crucial
to ensuring sustainable production of intensive crops, such as the tomato. Three experiments
were carried out to investigate the effects of pruning and fertilisation on growth and yield and
water and fertiliser use efficiency of hydroponic tomatoes.
In the first experiment the effect of EC (electrical conductivity), irrigation frequency
and growing media on water use, nutrient uptake, yield and quality of greenhouse tomato was
examined. A factorial design with split plots was used. Two EC treatments (1 and 2 mS.cm-1)
in factorial arrangement with 3 irrigation treatments (5x, 10x, 20x) were applied to the main
plots. Plants grown in different growing media (coir, sand, sawdust) represented the split
plots. Plants grown at EC 1 mS.cm-1 were still able to uptake sufficient nutrients to achieve
leaf nutrient contents associated with optimal production. Also, increasing the absolute
nutrient concentration had a small effect on nutrient uptake. The organic media, coir and
sawdust, reduced available N early in the tomato crop life, and tomatoes grown in coir had
reduced Ca uptake compared to plants grown in sand and sawdust. Coir grown plants used
more water compared to sand and sawdust grown plants. Plants grown at EC 1 mS.cm-1 used
less water compared to plants grown at EC 2 mS.cm-1. Tomatoes grown at an EC 1 mS.cm-1
did not differ significantly from higher EC plants in terms of marketable and green fruit yield.
Plants cultivated at the lower EC had significantly lower percentage soluble solids content
(Brix) compared to the higher EC treatment. The second experiment examined the effect of leaf and fruit pruning on fruit size,
total yield and marketable yield of tomatoes. Plants were grown using the high wire system
and pruned to two stems. Three different leaf pruning treatments were applied: no leaf
pruning, pruning every 2nd young leaf after 1m plant height, and pruning every 2nd young leaf
after 2m plant height. Two fruit pruning treatments were also applied: no fruit pruning and trusses pruned to 4 fruits. The experiment used a factorial design. Leaf pruning treatments
had no effect and this was probably due to too late a removal of young leaves. Fruit pruning
resulted in no significant difference between treatments in terms of marketable yield. Plants
with unpruned trusses did have a significantly higher total yield, higher early yield, lower
average marketable fruit weight, and higher yield of unmarketable fruit (particularly small
fruit compared to the pruned treatment). From these results it can be concluded that fruit
pruning isn’t necessary on short tomato crops but this may be different over a longer
cropping cycle.
The third experiment determined the combined effects of different EC and stem
pruning practices on nutrition, growth and early yield of hydroponically grown tomatoes in
coir. A factorial design was used, with two EC treatments (1 and 2 mS.cm-1) in factorial
arrangement with 2 stem pruning treatments (single and double). Stem pruning had little
effect on plant growth but did alter plant development. Plants pruned to two stems produced
significantly more trusses, but did not produce a significantly higher DM or leaf area
compared to single stem plants. Stem pruning’s major effect appears to be influencing fruit
load; this may in the long term result in differences in plant growth and nutrition. EC 1
mS.cm-1 plants produced significantly lower leaf area and organ dry masses but had a
significantly higher marketable yield compared to EC 2 mS.cm-1 plants. Over fertilisation in
young tomatoes can negatively impact on early yield, whereas lower fertiliser application in
early tomato growth improves early yield but limits canopy development which may limit
plant productivity in the long term. These differences in growth are believed to be primarily
related to differences in N and P nutrition. / AFRIKAANSE OPSOMMING: Die potensiële belang van grondlose produksietegnieke, veral by tamaties, in Suid-Afrika wat
toenemend meer water skaars raak, motiveer dat navorsing onder plaaslike toestande gedoen
moet word. By grondlose produksie stelsels word die toediening en die beskikbaarheid van
voedingstowwe nou gekoppel aan dié van water. Navorsing rakende metodes wat water en
kunsmis gebruiks doeltreffendheid sal verhoog en terselfdertyd besoedeling van die
omgewing voorkom asook die opbrengste en kwaliteit van tamaties behou of verbeter is dus
van uiterste belang. Swak bestuur van bemesting in hidroponiese stelsels gee aanleiding tot
water besoedeling en vermorsing van kosbare water en duur kunsmis. Snoei is 'n belangrike
kulturele praktyk om hoë produktiwiteit by hidroponiese tamaties te verseker. Die aanpassing
van snoei praktyke by klimaatstoestande is 'n goedkoop en doeltreffende manier om
produktiwiteit te verbeter sonder om insette te verhoog. Die verbetering van water en
kunsmis gebruiks doeltreffendheid is dus noodsaaklik om te verseker dat intensiewe gewasse,
soos tamaties, volhoubaar geproduseer word. Drie eksperimente is uitgevoer om die effek van
snoei en bemesting op die groei, opbrengs en water en kunsmis gebruiks doeltreffendheid van
hidroponiese tamaties te ondersoek.
In die eerste eksperiment is die effek van die EG, besproeiings frekwensie en
groeimedium op die water gebruik, voedingstofopname, opbrengs en kwaliteit van tamaties
ondersoek. 'n Faktoriaal ontwerp met gesplete plotte is gebruik. Twee EG behandelings (1 en
2 mS.cm-1), 3 besproeiings behandelings (5x, 10x, 20x per dag) en 3 groei media (kokos,
sand, saagsels) is ondersoek. Selfs by ‘n EG van 1 mS.cm-1 was die voedingstof opname van
plante vergelykbaar met waardes wat geassosieer word met blaar ‘n voedingstof inhoud wat
voorgeskryf vir optimale produksie. die verhoging van die absolute voedingstof konsentrasie
het ook 'n klein uitwerking op voedingstofopname gehad. In die organiese media - kokos en
saagsels – het die beskikbare N vroeg in die seisoen verminder, en die tamaties wat in kokos
gegroei het, het ook ‘n verminderde Ca opname getoon in vergelyking met die plante wat in
sand en saagsels gegroei het. Die plate wat in kokos gegroei het, het meer water gebruik in
vergelyking met plante wat in sand en saagsels gegroei het. Plante besproei met ‘n
voedingsoplossing van 1 mS.cm-1 EG het minder water gebruik as die plante wat besproei
met ‘n voedingsolossing by ‘n EG van 2 mS.cm-1. Tamaties wat gekweek word by 'n EG van
1 mS.cm-1 het nie beduidend verskil van hoër EG plante in terme van bemarkbare en groen
vrugte nie. Plante wat gekweek is by die laer EG het ‘n aansienlike laer persentasie oplosbare
vastestof inhoud (Brix) in vergelyking met die hoër EG-behandeling gehad. Die tweede eksperiment het die effek van blaar- en vrug snoei op die vruggrootte,
totale opbrengs en bemarkbare opbrengs van tamaties ondersoek. Plante is vertikaal opgelei
tot by die horisontale draad en na twee stamme gesnoei. Drie verskillende blaar snoei
behandelings is toegepas: geen blaar snoei, snoei elke 2de jong blaar na 1m plant hoogte en
snoei van elke 2de jong blaar na 2m plant hoogte. Twee vrug snoei behandelings is ook
toegepas: geen vrugte gesnoei en trosse gesnoei tot 4 vrugte. ‘n Faktoriale ontwerp is vir
hierdie eksperiment gebruik. Blaar snoei behandelings het geen effek gehad nie, waarskynlik
omdat die jong blare te laat verwyder was. Met die vrug snoei behandelings was daar geen
beduidende verskil tussen die behandelings in terme van bemarkbare opbrengs nie. Plante
waarvan die trosse nie gesnoei was nie het 'n aansienlik hoër totale opbrengs gelewer, asook
‘n hoër vroeë opbrengs maar ‘n laer gemiddelde bemarkbare vrug massa en ‘n hoër
persentasie onbemarkbare vrugte (baie klein vrugte in vergelyking met die gesnoeide
behandeling). Vanuit hierdie resultate kan daar afgelei word dat vrug snoei nie nodig is
tydens ‘n kort groeiperiode vir tamaties nie, alhoewel dit wel ‘n rol mag speel gedurende ‘n
langer groeiperiode.
Met die derde eksperiment is die gekombineerde effek van verskillende EG en stam
snoei praktyke op voeding, groei en vroeë opbrengs van hidroponies verboude tamaties
bepaal. 'n faktoriale ontwerp is gebruik, met twee EG behandelings (1 en 2 mS.cm-1) en 2
stam snoei behandelings (enkel en dubbel). Stam snoei het ‘n geringe uitwerking op die groei
van die plant gehad, maar het wel die ontwikkeling van plante verander. Plante gesnoei na
twee stamme het aansienlik meer trosse gehad, maar nie 'n hoër DM of blaar oppervlak as die
enkele stam plante nie. Stam snoei se grootste effek blyk te wees op die aantal vrugte per
plant en dit kan op die lang termyn lei tot verskille in die groei van plante en hul voeding. EG
1 mS.cm-1 plante het ‘n aansienlik laer blaaroppervlakte en droë massas geproduseer, maar
het 'n aansienlik hoër bemarkbare opbrengs in vergelyking met EG 2 mS.cm-1 plante gelewer.
Oorbemesting kan 'n negatiewe impak op die vroeë opbrengste van tamaties hê, terwyl laer
bemesting in die vroeë stadiums van groei vroeë opbrengs bevoordeel maar blaaroppervlak
ontwikkeling beperk wat dan ook produktiwiteit beperk in die lang termyn. Hierdie verskille
in groei word hoofsaaklik toegeskryf aan verskille in die N-en P-voeding.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/17940 |
| Date | 12 1900 |
| Creators | Fulton, Craig Mark |
| Contributors | Kempen, Estelle, Stellenbosch University. Faculty of AgriSciences. Dept. of Agronomy. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 81 p. : ill. |
| Rights | Stellenbosch University |
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