Effect of soil mineralogy and potassium buffer capacity on wine quality

Project Number
WW 13-15

Project title
Effect of soil mineralogy and potassium buffer capacity on wine quality

Project leader
Wooldridge, J

Project description
Grape vines tend to take up potassium (K) in excessive amounts (luxury consumption). This problem is exacerbated by the adequate to high levels of potassium in many South African vineyard soils, notably those derived from commonly occurring granite intrusive and shale formations. Since grape berries are powerful sinks for potassium, much of the potassium which is taken up is translocated to the fruit. High grape potassium concentrations in the juice lead to decreased free acids, lower tartrate: malate ratios, increased juice pH, unstable musts with an increased susceptibility to oxidative and biological spoilage and, ultimately, to high pH, low acidity, flat tasting wine. Colour may also be negatively affected by high potassium concentrations in the juice and wine because the extent to which anthocyanins ionise into their coloured forms decreases as pH increases.

Excessive potassium uptake is leading to reduced wine quality. Methods by which excessive potassium uptake may be moderated have not been widely investigated to date.

The ultimate objective of this project is to identify soil and vine parameters which are capable of being manipulated to yield a more beneficial level of potassium uptake and berry potassium content from a variety of soils. The objective during the first year of the project will be to establish a lysimeter trial to test the effects of soil parent material or mineralogy, liming, canopy management and irrigation on berry potassium content in grapevines.

Presentation(s)
Wooldridge, J. 2004. Soil clay mineralogy and potassium buffer capacity as potential wine quality determining factors in Western Cape vineyards. Paper presented at the 28th International Conference on Viticultural Zoning. 15-19 November, Cape Town, South Africa.

Wooldridge, J and Olivier, P. 2008. Soil parent material: A potential vine performance and wine style determining factor. Paper presented at the Combined Congress. 21-24 January, Grahamstown, South Africa.

Wooldridge, J and Van Schoor, L. 2008. Effects of geology, clay mineralogy and altitude on vine performance and wine style in Sauvignon blanc. Paper presented at the Combined Congress. 21-24 January, Grahamstown, South Africa.

Wooldridge, J and Olivier, O. 2008. Effects of soil parent material and rootstock on Merlot: Preliminary findings. Paper presented at the 31st National Congress of the South African Society for Enology and Viticulture. 11-14 November, Somerset West, South Africa.

Wooldridge, J. 2009. Differences in vine performance and wine characteristics in Merlot on soils derived mainly from granite and shade. Paper presented at the Combined Congress. 20-22 January, Stellenbosch, South Africa.

Wooldridge, J and Olivier, P. 2009. The role of geology in the terroir concept. Paper presented at the 4th International Congress of the South African Society for Enology and Viticulture. 28-30 July, Cape Town, South Africa.

Wooldridge, J. 2010. South African soils and wines. Paper presented at Ecovitis. 8-27 July, University of Siena, Italy.

Wooldridge, J and Olivier, P. 2010. The role of geology in the terroir concept. Paper presented at the 4th International Congress of the South African Society for Enology and Viticulture. 28-30 July, Cape Town, South Africa.

Wooldridge, J. 2011. Effects of lime / pH and parent material on cation buffer capacity and vine performance in upland soils of the Western Cape, South Africa. Paper presented at the International Conference on Environmental Technologies. 1-3 June, University of Pannonia, Veszprém, Hungary.

Olivier, M P and Wooldridge, J. 2012. Effect of soil parent material and rootstock on Merlot vine performance and wine quality. Paper presented at the Combined Congress. 16-19 January, Potchefstroom, South Africa.

Wooldridge, J and Olivier, P. 2012. Soil parent material and rootstock affect wine quality and performance in Merlot. Paper presented at the 34th National Congress of the South African Society for Enology and Viticulture. 14-16 November, Somerset West, South Africa.

Article
Olivier, P, Wooldridge, J. 2014. Effects of weathered granite and shale soils on Merlot grafted onto 1 10 Richter and 101-14 Mgt rootstocks in the Stellenbosch area, (p. 106-108)
Article.pdf

Olivier, P, Wooldridge, J. 2014. Die effek van verweerde graniet en skaliegrond in die Stellenbosch omgewing op Merlot wat op 110 Richter en 101-14 Mgt onderstokke geënt is, WineLand, Mnth Nov (p. 97-99)
Article.pdf

Wooldridge, J, Olivier, P. 2014. Effects of weathered soil parent materials on Merlot grapevines grafted onto 110 Richter and 101-4 Mgt rootstocks, South African Journal of Enology and Viticulture, v. 35 (1) (p. 59-67)
Article.pdf

FinalReport.pdf

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