Wine grapes

High wine grape yields are obtained on the most freely drained soils where water is not limiting. Vines will grow across a wide range of soil pHs, but extremes will render many nutrients unavailable and thereby restrict yield.

While smaller grapes may produce a more intensely flavored, quality wine, the grower needs to balance this with the need for a high yield from well-sized berries on his vines.

Nitrogen and phosphorus are significant in increasing wine grape berry set and weight.

The aim of any grower is a high yielding, top quality wine grape that satisfies the wine-maker. However, many vineyard managers and wineries believe that a high yielding grape crop cannot produce quality wine.

Strong vine canopies can lead to excessive nitrogen and potassium uptake, which increases grape and wine pH.

Growing temperature and grape variety are the major factors that influence the wine’s eventual color.

The amount of sugar in wine grape influences potential alcohol content after fermentation, and the amount of residual sugars remaining in the wine.

A certain level of acidity is considered important to the taste of any wine.

The total nitrogen content of wine grapes as well as the relative distribution of nitrogen compounds influences the production of yeast biomass and fermentation rate.

Grapes need to be free of the different disorders and rots in order to meet market requirements. The extent of these varies according to environmental conditions, varietal susceptibility and crop nutrition.

Grapes are subject to attack from a wide range of pests and diseases. Black rot, Botrytis, downy and powdery mildew are all caused by wet weather and if allowed to move from the leaf to the grape can cause considerable wine grape yield loss and quality deterioration.

Bunch stem necrosis (waterberry) in wine grape affects fruit set and fruit ripening. It can occur around the bloom, in which case it is called early bunch stem necrosis, at veraison or later. The occurrence of it is associated to weather conditions and crop nutrition.

Young vines with high levels of nitrate in the tissue often die or remain unproductive throughout the life of the vine. The disorder is known as ‘Merlot Disorder’. Symptoms of “Merlot disorder” are smaller leaves than usual, leaf-edge burn, poor leaf color and the wood fails to mature. Application of molybdenum significantly reduced the level of disorder.