Winegrowers generally agree that wines and grapes with low levels of nutrients have a more alkaline, less acidic, and rounder flavor. This is due to the minimum pH of the soil, which is inversely correlated with the depth of the clay horizon. The low nutrient levels in the upper layers of the soil cause roots to grow deeper, which helps to ensure a more consistent water supply to the vine. The pH of the wine was found to have no relation to the Brix index of the grape, total acidity of the wine, alcohol content, price per bottle, or date of harvest.
However, there was a direct relationship between the pH of the wine and the depth to the base of the clay horizon (Bw or Bt) of the soil (fig. Seguin could not find any reliable link between the chemical composition of the soil and the character or quality of the wine, but he did note that drainage properties of the soil affected water availability. The general consensus is that alkalinity and a less sour and more rounded flavor are improved in wines from low-nutrient soils. It is believed that it is the minimum pH of deep soil levels in Oregon that has the greatest impact on grape and wine pH (fig.
A common factor is pH, which can be objectively measured and is part of the flavor of wine, as well as an indicator of soil fertility. However, acidic wines from young soils are less likely to spoil than less acidic wines from old soils.
