The project aims to better understand the relationship between potassium levels in soil, vine and berry, and berry composition and wine acidity. A potassium management strategy will be devised so that the appropriate sugar-acid balance is achieved, particularly in warmer regions.
While potassium is integral to grape berry growth and development, it is well established that potassium - along with a decline in malate - has adverse effects on acid levels in grapes and wine. Relatively high pH (low acid) in wine requires expensive additions of tartaric acid, significantly increasing winemaking costs. Potassium also affects wine colour, can alter microbiological stability and fermentation processes, increases oxidative processes and potentially alters taste and mouthfeel in both red and white wines. It is an issue that affects warmer wine grapegrowing regions globally.
The project objective is to explore the potential to control berry pH in the vineyard through the addition of ameliorants to limit potassium uptake by the vines. Competing elements such as calcium or magnesium, which are antagonists for potassium uptake, will be applied by fertigation to both field vines and potted vines in a controlled setting. The partial substitution of these ions by the vine during root uptake may satisfy the essential physiological role of potassium in maintaining charge balance. Outcomes will be dependent on the properties of the soil (including its cation exchange capacity) and on the ability to separate the effects of elevated temperature on organic acid levels from those attributable to soil potassium uptake.
The results from this project will address an increasing consumer preference for minimal winemaking intervention, specifically reduced addition of tartaric acid, using vineyard management techniques. Input costs for wineries will be reduced and wine quality may be improved.