Die invloed van bemesting en lowerbestuur op die kaliuminhoud en pH van Cabernet sap en wyn

[摘要] ENGLISH ABSTRACT:In an attempt to reduce the pH of juice and wine, different fertiliser applications and canopymanagement 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 lateralshoots and yellow leaves in the bunch zone (Canopy 1); suckering (leaving three shoots perbearer), vertical shoot positioning as well as topping (Canopy 2); vertical shoot positioning andtopping (Canopy 3). The field trial was conducted in the Paardeberg region on the farmsMeerlus and Kersfontein. The vineyard at Meerlus was Cabernet franc/R99 with a highcanopy 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 CabemetSauvignon/101-14 Mgt with a lower canopy density and a less extensive root distribution, alsoestablished on a sandy loam soil of granite origin, but with a low top- and subsoil pH and ahigher K content.Fertilisation had no significant influence on the K content of juice and wine. Fertilisation withCa and Mg reduced the pH of juice significantly in the case of Meerlus. In contrast, Mgfertilisation increased the pH of juice significantly at Kersfontein. Lastly, fertilisation had nosignificant effect on the pH of the wine. The K content of the juice at Meerlus was significantlyreduced by Canopy 3 in comparison with Canopy 1 and 2. However, in contrast with Canopy1 and 3, Canopy 2 significantly increased the pH of juice at Meerlus. The K content of thejuice at Kersfontein was significantly reduced by Canopy 1, compared to Canopy 2 and 3, withno significant effect on the pH of the juice. Canopy management had no significant effect onwine pH.It appears to be possible to reduce the pH of juice in the case of Cabernet franc/99R, situatedon granite soils, by means of Ca and Mg fertilisation. Because Ca(OH)2 and MgS04fertilisation increased the maturity of Cabernet Sauvignon/101-14 Mgt grapes, it wasimpossible to evaluate the effect of fertilisation on the pH of juice at Kersfontein. The generalphenomenon that a high canopy density results in a high pH of juice and wine, was notobserved in this field trial. The possible reasons for this were the low canopy density of thecontrol plots, as well as the difference in maturity between canopy management treatments.

[发布机构] Stellenbosch University