Besides that which is essential for photosynthesis, namely carbon dioxide, water, and sunlight, grapevines also require a range of nutrients in order to grow, survive and prosper. These nutrients are split into two groups depending on scale of requirement, macro and micronutrient, the former being those required in larger amounts. Potassium is the second most abundant mineral nutrient in plants and has a number of roles. It is associated with the movement of water, nutrients and carbohydrates whilst also helping to regulate stomata and supporting enzyme activation. A deficiency can reduce yields, fruit quality and increase susceptibility to disease. Too much can cause a finished wine to lose acidity. In this article I will explore potassium in viticulture from soil to bottle.