Agronomic Principles

There are a large number of factors that affect top quality wine production. Many are within the control of the grower, under given climatic and soil conditions.

Climatic Zone 

Wine grapes are traditionally best grown between 34-49° latitude in both the northern and southern hemisphere. They can though be grown outside this zone on sun-facing slopes at low altitudes. The mean maximum temperature of the warmest month of production should be above 18-20°C and above freezing in the coldest month. 

For best growth, grapes require long, dry, hot summers and cool winters. High humidity increases disease and pest risk. Rain or cloudy conditions during blooming can result in poor fruit set. Rain at maturity increases fruit rot. 

A long growing season is needed to mature the fruit, and rain, while desirable in the winter, can be supplemented by irrigation. It is difficult to obtain red wines of deep colour in cool growing conditions.

Cover Crops 

Cover crops are grown to prevent wind or soil erosion especially on sandy soils. They also minimize dust on the grape bunch. In some regions, cover crops are not usually grown until the vine roots are well established (4 – 5 years old), that competition of cover crops for nutrient and moisture is minimized and thus vine productivity is not harmed.

Wine Grape

Grass cover crops in wine grape.

Wine Grape

Legume cover crops in wine grapes.

Rootstock 

The choice of the rootstock will directly influence the yield, vigor and performance of the grape vine. Rootstocks vary in their tolerance and sensitivity to specific conditions (e.g. pH, lime, salt/water stress, diseases). Soil factors including natural fertility, past management, and available soil moisture can have a significant role in rootstock selection, vine spacing, and cultural practices.

Selection of rootstocks with high nutrient uptake efficiency, well adapted to the soil and climate, will decrease production costs and contribute to the sustainability and competitiveness of grape wine production. The ability of different rootstocks to extract nutrients is related to the spatial root distribution and root diameter, as well as the form in which the nutrient is normally assimilated by the root. Thus, good soil structure is important.

The choice of an appropriate rootstock can also have many viticultural management advantages such as giving tolerance to Phylloxera, nematode and soils with a high salt or lime content.

Crop Manipulation 

Training of vines – the shaping of the rootstock and the vine stock – aims to adjust the balance of foliage and fruit on the vine. 

Pruning in the winter prepares the next year's harvest on entirely new growth. In the first 3-4 years it provides a satisfactory shape for the vine. In the following years, the bulk of the previous season's growth is short pruned, leaving only two to six canes. These are reduced in length according to the vigor of the vines. 

In-season removal of basal leaves and newly grown lateral shoots, just prior to fruit set, opens up the vine canopy, allowing better light and spray penetration as well as bringing forward maturity.

Mechanical Pruning

Training of vines – the shaping of the rootstock and the vine stock – aims to adjust the balance of foliage and fruit on the vine. Pruning in the winter prepares the next year's harvest on entirely new growth. In the first 3-4 years it provides a satisfactory shape for the vine. In the following years, the bulk of the previous season's growth is short pruned, leaving only two to six canes. These are reduced in length according to the vigor of the vines.

In-season removal of basal leaves and newly grown lateral shoots, just prior to fruit set, opens up the vine canopy, allowing better light and spray penetration as well as bringing forward maturity.