Thesis (MScAgric)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Shiraz/110R grapevines, growing in a fine sandy loam soil in the Breede River Valley,
were subjected to ten different drip irrigation strategies during the 2006/07, 2007/08
and 2008/09 seasons. Grapevines of the control treatment (T1) were irrigated at 30%
to 40% plant available water (PAW) depletion throughout the growing season.
Grapevines of three treatments were irrigated at 70% to 80% PAW depletion from bud
break until véraison (i.e. when ca. 95% of grape berries have changed colour),
followed by either irrigation at 30% to 40% PAW depletion (T2) or a continuous deficit
irrigation (CDI) strategy (T3) or irrigation at 70% to 80% PAW depletion (T4) during
ripening. The CDI strategy was obtained by applying ca. half the volume of water that
was applied to the control. This allowed the soil to dry out gradually between
physiological stages (i.e. bud break and véraison or véraison and harvest).
Grapevines of three further treatments were irrigated at ca. 90% PAW depletion from
bud break until véraison, followed by irrigation at 30% to 40% PAW depletion (T5) or a
CDI strategy (T6) or irrigation at ca. 90% PAW depletion (T7) during ripening.
Grapevines of two treatments were irrigated by means of a CDI strategy from bud
break until véraison. For both treatments, the soil water content (SWC) was allowed
to dry out gradually until ca. 90% PAW depletion was reached. After véraison, the
SWC of the one treatment was maintained at ca. 90% PAW depletion by applying only
four small irrigations of three hours each during ripening (T8). The soil of the other
treatment, received an irrigation at véraison to refill the SWC to field capacity (T9)
followed by the CDI strategy during ripening. Grapevines of the tenth treatment were
irrigated at ca. 90% PAW depletion between bud break and véraison followed by a
partial profile refill (PPR) strategy during ripening (T10). In order to obtain the PPR
strategy, SWC was only maintained between 40% and 60% PAW depletion.
Evapotranspiration varied between 3.5 mm/day and 0.1 mm/day for driest and wettest
treatments, respectively, during the period between December and February. This
was substantially less than the volumes required for full surface irrigation. For
irrigations applied at 30% to 40% PAW depletion (T1), 70% to 80% PAW depletion
(T4) and ca. 90% PAW depletion (T7) levels throughout the season, crop coefficients
for the Penman-Monteith reference evapotranspiration (ETo) were 0.4, 0.2 and 0.1,
respectively. Under the given conditions, the different irrigation strategies did not have any effect
on root distribution and density. Shoot growth of grapevines exposed to high to
severe water deficits in the pre-véraison period stopped before mid December.
Shoots of grapevines that were exposed to high or severe water deficits before
véraison followed by more frequent irrigation during ripening showed active
re-growth. These trends occurred during all the seasons.
The level of PAW depletion reflected strongly in the plant water potential in the
grapevines. Leaf water potential was influenced by the prevailing atmospheric
conditions, whereas stem water potential was less sensitive to atmospheric
conditions, but responded more directly to soil water availability. Due to the good
relationships between pre-dawn leaf, mid-day leaf, mid-day stem and total diurnal
water potential, it was possible to re-classify the water status in terms of previous
classifications for these water potentials based on pre-dawn measurements. Water
constraints in T1, T2 and T5 grapevines were classed as experiencing no stress,
whereas the T7 and T8 ones experienced strong to severe water constraints before
harvest.
High frequency irrigation strategies during ripening delayed sugar accumulation due
to dilution of sugar in the larger berries. Except for the wettest strategy, and where
grapevines were subjected to the CDI strategy throughout the season, berry mass
increased during ripening, i.e. from véraison to harvest. Water deficits had a negative
effect on berry mass, bunch size and yield. Where higher soil water depletion levels
were allowed, irrigation strategies had a positive effect on the irrigation water
productivity of grapevines compared to the frequently irrigated or CDI strategies.
Higher water constraints in grapevines, particularly during ripening, improved
sensorial wine colour and enhanced some of the more prominent wine aromas, e.g.
spicy and berry. Grapevines that were irrigated at a high frequency during ripening
produced wines with diluted character flavours and aromas and inferior overall
quality. Under the given conditions, sensorial wine colour and spicy character were
the dominant factors in determining overall sensorial wine quality. / AFRIKAANSE OPSOMMING: Shiraz/110R wingerdstokke in ‘n fyn sandleem grond in die Breede Rivier vallei is
gedurende die 2006/07, 2007/08 en 2008/09 seisoene met tien verskillende
drupbesproeiingstrategieë besproei. Wingerdstokke van die kontrole (B1) is deur die
seisoen by 30% to 40% plant beskikbare water (PBW) onttrekking besproei. Drie
behandelings is tussen bot en deurslaan (wanneer ca. 95% van die korrels verkleur
het) by 70% tot 80% PBW onttrekking besproei, gevolg deur besproeiing by 30% tot
40% PBW onttrekking (B2), ‘n deurlopende tekort besproeiing (DTB) strategie (B3) of
besproeiing by 70% tot 80% PBW onttrekking (B4) gedurende rypwording. In die
geval van die DTB strategie is ongeveer die helfte van die volume water toegedien
wat by die kontrole toegedien is. Laasgenoemde strategie het die grond toegelaat om
geleidelik tussen fisiologiese fases (i.e. tussen bot en deurslaan of tussen deurslaan
en oes) uit te droog. Drie ander behandelings is by ca. 90% PBW onttrekking tussen
bot en deurslaan besproei, gevolg deur besproeiing by 30% tot 40% PBW onttrekking
(B5) of ‘n DTB strategie (B6) of besproeiing by ca. 90% PBW onttrekking (B7)
gedurende rypwording. Wingerdstokke van twee ander behandelings is d.m.v. ‘n
DTB strategie vanaf bot tot deurslaan besproei. Beide behandelings se
grondwaterinhoud (GWI) was toegelaat om geleidelik uit te droog tot ca. 90% PBW
onttrekking bereik was. Na deurslaan was die GWI van die een behandeling naby ca.
90% PBW onttrekking gehandhaaf deur slegs vier klein besproeiings van drie uur elk
gedurende rypwording toe te pas (B8). Die grond van die ander behandeling het
tydens deurslaan ‘n besproeiing ontvang om die GWI tot by veldkapasiteit te hervul
(B9) en is tydens rypwording weer d.m.v. ‘n DTB strategie besproei. Stokke van die
tiende behandeling is tussen bot en deurslaan by ca. 90% PBW onttrekking besproei,
gevolg deur besproeiing d.m.v. ‘n gedeeltelike profiel hervul (GPH) strategie tydens
rypwording (B10). Om ‘n GPH strategie toe te kon pas, is tussen 40% en 60% PBW
ontrekking gehandhaaf.
Evapotranspirasie het tussen 3.5 mm/dag en 0.1 mm/dag vir onderskeidelik die
natste en droogste behandelings tussen Desember en Februarie gevarieer. Dit was
aansienlik laer as volumes wat vir voloppervlak besproeide wingerde benodig word.
In die geval van besproeiing by 30% tot 40% PBW onttrekking (B1), 70% tot 80%
PBW onttrekking (B4) en ca. 90% PBW onttrekking (B7) deur die loop van die seisoen was die gewasfaktore vir die verwysingverdamping (ETo) 0.4, 0.2 en 0.1
onderskeidelik.
Onder die gegewe toestande het die verskillende besproeiingstrategië geen effek op
die worteldigtheid en –verspreiding gehad nie. Lootgroei van wingerdstokke wat aan
hoë tot baie hoë watertekorte blootgestel was voor deurslaan, het voor middel
Desember gestop. Lote van wingerdstokke wat aan hoë tot baie hoë watertekorte
voor deurslaan blootgestel is, gevolg deur besproeiing teen ’n hoë frekwensie tydens
rypwording, het aktiewe hergroei getoon.
Die PBW ontrekkingspeil het sterk in die plantwaterpotensiale van wingerdstokke
weerspieël. Blaarwaterpotensiaal is deur heersende klimaatstoestande beïnvloed,
terwyl stamwaterpotensiaal minder sensitief teenoor die klimaat was, maar meer
direk deur die beskikbaarheid van grondwater beïnvloed is. Vanweë die goeie
verband tussen voordagbreek blaar-, mid-dag blaar-, mid-dag stam- en totale
daaglikse waterpotensiaal, was dit moontlik om water status van die stokke te
her-klassifiseer in terme van vorige vir waterpotensiaalklassifikasies wat op
voordagbreek waardes gebasseer is. Waterspanning in B1, B2 en B5 stokke is as
geen spanning geklassifiseer, terwyl dié van B7 en B8 voor oes in die hoë tot baie hoë
klasse geval het.
Hoë frekwensie besproeiing strategieë gedurende rypwording kan suikertoename
a.g.v. die groter korrels vertraag. Met die uitsondering van die natste strategie, asook
waar stokke volgens die DTB strategie deur die seisoen besproei is, het korrelmassa
gedurende rypwording toegeneem. Watertekorte het ’n negatiewe effek op
korrelmassa, trosgrootte en produksie gehad. Besproeiingstrategieë waar ’n hoë
mate van grondwateronttrekking voor besproeiings toegelaat is, het ’n positiewe effek
op die besproeiingwaterproduktiwiteit van wingerd in vergelyking met gereelde
besproeiings of ‘n DTB strategie gehad.
Watertekorte, veral gedurende rypwording, het ’n verbetering in sensoriese wynkleur
en meer prominente wyn aromas, tot gevolg gehad. Besproeiing teen hoë
frekwensies gedurende rypwording, het wyne met ’n afgewaterde smaak en aroma
karakters asook ’n swak algehele gehalte produseer. Sensoriese wynkleur en
spesery karakter die dominante faktore in die bepaling van algehele kwaliteit.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/17866 |
| Date | 12 1900 |
| Creators | Lategan, Eugene Lourens |
| Contributors | Hoffman, J. E., Myburgh, P. A., Stellenbosch University. Faculty of AgriSciences. Dept. of Soil Science. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 1 v. ( various pagings) : ill., map. |
| Rights | Stellenbosch University |
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