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Nutritional status of geologically different vineyards in HelderbergShange, Philisiwe Lawrancia 12 1900 (has links)
Thesis (MscAgric (Viticulture and Oenology))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Little scientific information regarding the effect of different geological parent materials on
grapevine performance is currently available in South Africa. This aspect is of special
significance for the Helderberg area, where parent material may change from granite to shale
over a short distance. This results in shale- as well as granite-derived soils often occurring
within the same vineyard. The objectives of this study were to (i) quantify the nutritional status
and other soil properties of different parent materials (shale and granite) and overlying soils (ii)
investigate the impact of geological differences in the soil on the vine nutritional status and
certain vine parameters. This study was done over two seasons (2006/2007 and 2007/2008).
Two Sauvignon blanc and two Cabernet Sauvignon vineyard blocks were selected at two
different localities for each cultivar in the Helderberg area, South Africa. Shale- and granitederived
soils were identified within each block.
Kaolinite was the dominant mineral, whereas quartz and feldspar were sub-dominant. Traces of
mica were also present in some shale- and granite-derived soils. Granite- contained significantly
higher contents of coarse sand than shale-derived soils, whilst the opposite occurred in terms of
fine sand. These differences affected the water holding capacity, in general making it higher in
shale- than granite-derived soils. Shale-derived soils had higher concentrations of total K but
granite-derived soils had a higher ability to release K as they contained higher concentrations of
soluble K. The Q/I parameters, potential buffering capacity of K (PBCK) and equilibrium activity
ratio of K (ARK) showed no consistent responses to geological differences.
Potassium concentrations were higher in the leaf blades (obtained before harvest in 2007) from
Sauvignon blanc grapevines on granite- than on shale-derived soils. Potassium concentrations
in the Cabernet Sauvignon juice (obtained in 2007) tended higher in juice from granite- than
from shale-derived soils. In 2008, K concentrations tended higher in juice from shale- than from
granite-derived soils for both cultivars. The pH of the Sauvignon blanc juice (obtained in 2008)
tended higher in juice from shale-than from granite-derived soils, thus corresponding with the K
concentrations in the juice in this season. Nitrogen concentrations were higher in Cabernet
Sauvignon juice (obtained in 2007) and Sauvignon blanc juice (obtained in 2008) from shalethan
from granite-derived soils. In terms of vine water status, vines on granite-derived soils
appeared more stressed than those on shale-derived soils in both seasons at one of the
vineyards.
In these Sauvignon blanc and Cabernet Sauvignon vineyards, the K nutritional status was not
affected by geology in a consistent manner but there were some noticeable tendencies for a
specific cultivar during certain seasons. On account of vines being planted on shale- and
granite-derived soils within the same block, soil preparation was done similarly for both soils,
and they were exposed to similar irrigation schedules, canopy management strategies and
climatic conditions. Therefore, there is a high probability that all these practices may have
negated the effect of geology on the K status of soils and especially on juice K concentration at
the time of harvest. It was clear that seasonal differences and fertilisation affected the nutritional
status of the vines more than geology. / AFRIKAANSE OPSOMMING: In Suid-Afrika is daar tans min wetenskaplike inligting oor die effek van verskillende geologiese
moedermateriale op die prestasie van wingerd beskikbaar. Hierdie aspek is veral van belang in
die Helderberg-area, waar moedermateriaal oor ‘n baie kort afstand van graniet na skalie kan
wissel. Dit lei daartoe dat skalie-, sowel as granietgronde, dikwels binne dieselfde wingerd
voorkom. Die doelwitte van die studie was om: (i) die voedingstatus en ander grondkundige
eienskappe van die verskillende moedermateriale (skalie en graniet) en oorliggende gronde te
kwantifiseer (ii) die impak van geologiese verskille in die grond op wingerd se voedingstatus en
sekere wingerdkundige parameters, te ondersoek. Hierdie studie is oor twee seisoene
(2006/2007 en 2007/2008) gedoen. Twee Sauvignon blanc en twee Cabernet Sauvignon
wingerdblokke is geselekteer by twee verskillende lokaliteite vir elke kultivar in die Helderbergarea,
Suid-Afrika. Beide skalie- en granietgrond is binne elke blok geïdentifiseer.
Kaoliniet was die dominante mineraal, met kwarts en veldspaat sub-dominant, terwyl spore van
mika ook in beide skalie- en granietgronde gevind is. Granietgronde het betekenisvol hoër
hoeveelhede growwe sand bevat, terwyl skaliegronde meer fyn sand bevat het. Hierdie verskille
het ‘n effek op waterhouvermoë gehad en daartoe gelei dat waterinhoude oor die algemeen
hoër was vir skaliegronde. Skaliegronde het groter hoeveelhede totale K bevat, maar
granietgronde se vermoë om K vry te stel was hoër, omdat hulle ‘n hoër konsentrasie oplosbare
K bevat het. Die Q/I parameters, potensiële buffervermoë vir K (PBCK) en ewewig
aktiwiteitsverhouding vir K (ARK), is nie op ‘n konsekwente wyse deur geologiese verskille
beïnvloed nie.
Vir die Sauvignon blanc wingerde was kalium konsentrasies in blaarskywe (gemonster voor oes
in 2007) hoër vir graniet- as vir skaliegronde. Kalium konsentrasies in die sap vanaf Cabernet
Sauvignon (gemonster in 2007) het hoër geneig vir granietgronde. In 2008 het die kalium
konsentrasies, vir beide kultivars, hoër geneig in sap vanaf skaliegronde. Gedurende dié
seisoen het die pH van sap ook hoër geneig vir Sauvignon blanc vanaf skaliegronde, wat dus
ooreenstem met die K inhoud van die sap. Stikstof konsentrasies was hoër in sap vanaf
skaliegronde vir Cabernet Sauvignon (2007) en vir Sauvignon blanc (2008). In terme van die
wingerde se waterstatus, het stokke op die granietgrond, by een van die lokaliteite, geneig om
gedurende beide seisoene onder groter stremming te wees op graniet as op skaliegrond.
In hierdie Sauvignon blanc en Cabernet Sauvignon wingerde, is K voedingstatus nie op ‘n
konsekwente wyse deur geologie geaffekteer nie, maar gedurende sommige seisoene was daar
wel duidelike tendense vir ‘n spesifieke kultivar. Omdat die stokke binne dieselfde blok op
skalie- en graniet gronde geplant is, was grondvoorbereiding eenders vir die twee grondtipes
terwyl besproeiingskedule, lowerbestuur en klimaatstoestande ook identies was. Daar is dus ‘n
hoë waarskynlikheid dat al hierdie faktore daartoe kon bygedra het dat die effek van geologie
op die K status van van gronde versluier is, veral die effek op die K inhoud van sap teen oestyd.
Dit was duidelik dat seisoenale klimaatsverskile en bemestingspraktyke ’n groter effek as
geologie op die voedingstatus van die wingerd gehad het.
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Source and identity of insect contaminants in export consignments of table grapesPryke, James Stephen 03 1900 (has links)
Thesis (MScAgric (Conservation Ecology and Entomology)--University of Stellenbosch, 2005. / The South African table grape industry exports approximately 60% of the table
grapes produced. A major threat to the export of these grapes is the phytosanitary risk
that insect pests pose. This study was conducted in the Hex River Valley, South
Africa’s main table grape producing area. The aim of this study was to reduce the
number of phytosanitary rejections from insects on table grapes from the Hex River
Valley. Thus the main objectives of the study were to identify the most important
phytosanitary pests in the Hex River Valley; the determination of their presence in the
vineyards with possible means to control them; and to assess the possibility of using
postharvest quarantine treatments in the Western Cape. Further aims were to
determine the effect of different colour harvesting crates on the phytosanitary pests and
whether the phytosanitary pests infested the grapes via packhouses.
The most important phytosanitary pests of table grapes of the Hex River Valley
are in order of importance: Phlyctinus callosus (Schonherr) (Coleoptera: Curculionidae),
Epichoristodes acerbella Walker (Lepidoptera: Tortricidae), Planococcus ficus
(Signoret) (Hemiptera: Pseudococcidae), Ceratitis capitata (Wiedemann) (Diptera:
Tephritidae), Gonocephalum simplex Fabricius (Coleoptera: Tenebrionidae) and
Dysdercus fasciatus Signoret (Hemiptera: Pyrrhocoridae). 12.71% of rejections were
from species that were not identified, while a further 33% of the rejections were possibly
identified incorrectly.
Phytosanitary control of P. callosus appeared to be far more effective using
Plantex® than pesticides. Weather conditions appeared to affect the abundance of P.
callosus, especially warm weather, while bunches harboured less P. callosus later in
the day. Control of E. acerbella with DiPel® (Bacillus thuringiensis var. kurstaki)
appeared to at least reduce the population within the vineyards, and so its use is
recommended. P. ficus is a non-actionable species for the USA market and is not
listed as a phytosanitary pest for the Israeli market and so should not be causing any
phytosanitary rejections. C. capitata appeared to be successfully controlled by the fruit
fly sterile release program and the cold sterilisation it currently undergoes. G. simplex
caused few rejections. It is still unclear where this pest infests the grapes, as it was found in both the field and in the packhouses. D. fasciatus occurrence on grapes was
probably accidental. It was shown that picking during the early and late parts of the
day, when this species was less active, reduced its occurrence in bunches. Gryllus
bimaculatus (De Geer) (Orthoptera: Gryllidae), although not reported as a reason for
rejections in table grapes for the past two years, was an actionable species that was
present in large numbers in the Hex River Valley. There was a strong correlation
between increasing quantities of pesticides and higher abundances of G. bimaculatus.
It appeared to be an indicator of the overuse of pesticides. Results of this study
showed that infestation by the phytosanitary pests came from neighbouring vineyards.
The creation of barriers to prevent the movement of these pests between vineyards is
suggested.
Methyl bromide is the most commonly used postharvest quarantine treatment.
Owing to the ozone-depleting properties of methyl bromide, it is scheduled to be
outlawed in many countries from 2005. Alternative postharvest treatments are
irradiation, extreme temperatures, forced air, vapour-heat treatments and the use of
controlled atmospheres. Irradiation treatments appeared to control the pests at doses
that do not damage the grapes. Controlled atmosphere treatments also have a high
probability of success, although more research is required on this treatment. Low
temperature treatments are relatively cheap as most exported fruit already undergoes
cold storage, and appears to control species in the families Pseudococcidae and
Tephritidae, although further research is required for the other pest.
Colour or location of the harvesting crates in the vineyards appeared not to
influence the number of phytosanitary pests collected, as they were not attracted to
these crates.
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