Thesis (MScAgric)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: In an attempt to reduce the pH of juice and wine, different fertiliser applications and canopy
management practices were evaluated in a field trial. Fertiliser treatments consisted of no,
CaS04, Ca(OH)2, and MgS04 fertilisation. Canopy management was as follows: suckering
(leaving only two shoots per bearer), tipping, vertical shoot positioning and removal of lateral
shoots and yellow leaves in the bunch zone (Canopy 1); suckering (leaving three shoots per
bearer), vertical shoot positioning as well as topping (Canopy 2); vertical shoot positioning and
topping (Canopy 3). The field trial was conducted in the Paardeberg region on the farms
Meerlus and Kersfontein. The vineyard at Meerlus was Cabernet franc/R99 with a high
canopy density and a good root distribution, established on a sandy loam soil of granite origin,
with a low subsoil pH and a high K content. The vineyard at Kersfontein was Cabemet
Sauvignon/101-14 Mgt with a lower canopy density and a less extensive root distribution, also
established on a sandy loam soil of granite origin, but with a low top- and subsoil pH and a
higher K content.
Fertilisation had no significant influence on the K content of juice and wine. Fertilisation with
Ca and Mg reduced the pH of juice significantly in the case of Meerlus. In contrast, Mg
fertilisation increased the pH of juice significantly at Kersfontein. Lastly, fertilisation had no
significant effect on the pH of the wine. The K content of the juice at Meerlus was significantly
reduced by Canopy 3 in comparison with Canopy 1 and 2. However, in contrast with Canopy
1 and 3, Canopy 2 significantly increased the pH of juice at Meerlus. The K content of the
juice at Kersfontein was significantly reduced by Canopy 1, compared to Canopy 2 and 3, with
no significant effect on the pH of the juice. Canopy management had no significant effect on
wine pH. It appears to be possible to reduce the pH of juice in the case of Cabernet franc/99R, situated
on granite soils, by means of Ca and Mg fertilisation. Because Ca(OH)2 and MgS04
fertilisation increased the maturity of Cabernet Sauvignon/101-14 Mgt grapes, it was
impossible to evaluate the effect of fertilisation on the pH of juice at Kersfontein. The general
phenomenon that a high canopy density results in a high pH of juice and wine, was not
observed in this field trial. The possible reasons for this were the low canopy density of the
control plots, as well as the difference in maturity between canopy management treatments. / AFRIKAANSE OPSOMMING: In 'n poging om die pH van sap en wyn te verlaag, is die effek van verskillende bemesting- en
lowerbestuursfaktore in 'n veldproef geêvalueer. Bemesting het bestaan uit geen, CaS04,
Ca(OH)2 en MgS04 toediennings. Lowerbestuur was: suier tot twee lote per draer, tip,
vertikale lootposisionering, verwydering van sylote en geel blare in trossone (Lower 1); suier
tot drie lote per draer, top en vertikale lootposisionering (Lower 2); top en vertikale
lootposisionering met geen suier nie (Lower 3). Die veldproef is op twee plase nl. Meerlus en
Kersfontein, in die Paardeberg omgewing uitgevoer. Die wingerd by Meerlus was Cabernet
franc/R99 met 'n hoë lowerdigtheid en goeie wortelverspreiding, wat op 'n sandleemgrond van
graniet oorsprong met In lae ondergrond-pH en hoë K-inhoud gevestig is. Die wingerd by
Kersfontein het bestaan uit Cabernet Sauvignon/101-14 Mgt met 'n laer lowerdigtheid en
swakker wortelverspreiding, wat op In sandleemgrond van graniet oorsprong met In deurgaans
lae grond-pH en baie hoë K-inhoud gevestig is.
Bemesting het geen betekenisvolle invloed op die K-inhoud van sap en wyn gehad nie. By
Meerlus het Ca- en Mg-bemesting egter die pH van sap betekenisvol verlaag. In teenstelling
hiermee het Mg-bemesting die sap-ph by Kersfontein betekenisvol verhoog. Bemesting het
verder geen betekenisvolle invloed op die pH van wyn gehad nie. Lower 3 het die K-inhoud
van sap by Meerlus betekenisvol verlaag in vergelyking met Lower 1 en Lower 2. By
Kersfontein was die K-inhoud van sap by Lower 1 betekenisvollaer as by Lower 2 en Lower 3.
Teenoor Lower 1 en Lower 3 het Lower 2 'n betekenisvol hoër sap-pH by Meerlus tot gevolg
gehad. Lowerbehandelings het egter geen betekenisvolle invloed op die pH van wyn gehad
nie.
Die moontlikheid bestaan dus om die sap-pH van Cabernet franc/R99 op granietgrond
betekenisvol m.b.v. Ca- en Mg-bemesting te verlaag. Aangesien Ca(OH)2- en MgS04- bemesting die rypheidsgraad van Cabernet Sauvignon/101-14 Mgt se druiwe betekenisvol
verhoog het, was dit onmoontlik om die effek van bemesting op sap-pH by Kersfontein te
evalueer. Die algemene verskynsel dat 'n hoë lowerdigtheid tot hoë pH's in sap en wyn lei, is
nie in die proef ondervind nie. Die lae lowerdigtheid van die kontrole persele en die verskil in
rypheidsgraad tussen lowerbehandelings kan moontlik as rede hiervoor aangevoer word.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/52781 |
| Date | 03 1900 |
| Creators | Engelbrecht, G. P. |
| Contributors | Saayman, D., Fey, M., Stellenbosch University. Faculty of AgriSciences. Dept. of Viticulture and Oenology. Institute for Wine Biotechnology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | af_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 130 p. |
| Rights | Stellenbosch University |
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