sábado, 6 de junio de 2015
GRAFTING: Generally speaking, it is the connection of two pieces of living plant tissue so that they unite and grow as one. Vines are grafted or budded to take advantage of the desirable properties of the rootstock variety. The choice of the rootstock is just as important as the scion (which determines the actual grape variety), for it has to be adapted to the soil and the climate of the vineyard and to the V.Vinifera variety marked by the scion used.
The crucial factor in the development of modern viticulture came with the wholesale destruction of European vineyards by the Phylloxera aphid in the second half of the 19th century. As V. Vinifera vines were killed off by the louse, growers rapidly had to find alternative vines to produce grapes. After a number of attempts using different alternatives (V. Labrusca, crossings, etc), eventually, it was discovered that the European V. Vinifera could be grafted on to American rootstocks (resistant to Phyloxera), and would thereby be protected.
The uniting of the scion with the rootstock is achieved by a slow growth process. A grafting machine makes cuts through the vine rootstock and scion pieces with mirror-image shapes that permit a perfect fitting.
PLANTING: A grower may plant a vine for two reasons: either to establish a new vineyard or to replace old vines.
Generally speaking, the older the vine is, the finer the wine it produces. However, the lower its yield. The main aim of any grower is to produce a profit, so a balance has to be reached between quantity and quality. Generally, vines will be grubbed up when they are between 35 and 50 years old.
When planting a new vineyard, the following considerations should be taken into account:
- Location: bearing in mind the influences of topography and desired exposure.
- Planting density: It may vary from 3,000 vines per hectare, up to 10,000 or more. Apart from the factors listed above, this decision will be based on how much stress the grower wants to place upon the vines; the theory being the more vines per hectare, the greater the stress, the better the wine that is produced.
- Planting layout: the way the plants are arranged starting from a given planting density. Layout can be square, rectangular or triangular and a given row distance and planting level has to be determined. These choices depend on growing conditions and particularly on the need for mechanisation.
Once the plantation has been carried out, the vine’s shape will be governed by the way in which the vine grower prunes and trains it.
PRUNING: It involves cutting off unwanted vegetative parts in the form of canes in winter. There are also pruning operations consisting in cutting off unwanted vegetative growth in the form of excess shoots in early spring (Spring pruning- Poda en verde) and shoot tips in summer (Tipping - despunte).
There are several reasons for pruning:
- To select the buds that will form shoots in the next harvest and to prepare the vine for fruiting in future harvests.
- To limit the production of the vine and reach a balanced load that will lead to quality grapes.
- To restrict the vegetation, to concentrate the vigour of the vine into the production of fruit.
- To control the leaf canopy so that the bunches of grapes have the optimum exposure to the sun and aeration to limit potential fungal infection.
- To keep the vineyard tidy to ease work throughout the growing season and vintage.
TRAINING: The training system is very important in vine cultivation, because of its direct influence on production and grape quality. Training aims to favour leaf and cluster sun exposure and to facilitate plant ventilation.
The training system used will relate to the type of pruning employed. With the use of machine picking, wire training is becoming more common, since it enables a wider spacing between the rows of vines. There are two main options for training:
- Goblet training: This is a free-standing system, i.e., without any support for the vine, of low height, short pruning and low loads. It is appropriate for dry soils with a large amount of light. The closed canopy protects the plant against excessive temperatures and water loss through transpiration.
- Trellising: This is a high, long pruning, system that requires a physical support for the vines. The system entails reduced vine growth potential because of the long trunk and arms and because the berries are further away from the soil and its heat radiation. This results in a general delay in ripening. The long arms and trunk require water to travel longer distances, so the plants are more susceptible to drought. Espalier training is therefore only used when the climate is suitable or when irrigation systems can be used. It allows for mechanisation. It is also possible to modify the plant’s microclimate and improve cluster and leaf surface sun exposure.
OTHER VINEYARD OPERATIONS:
- Tillage (laboreo): Is the oldest task in vine cultivation. Tillage operations improve soil structure, making it more permeable to water and air, particularly in the case of compact clay soils. Soft soils make it easier for water to permeate to greater depths, thereby creating a very valuable reserve for vine development during dry periods.
- Cover crops (cubierta vegetal): By planting certain herbaceous species between vineyard rows, certain goals are achieved naturally.
- Soil fertilisation: With natural and chemical fertilisers to ensure the vine is adequately fed with nitrogen, phosphorus, potassium, etc., making up for soil deficiencies to a certain extent.
- Plant protection treatments: Against weeds and attacks from pests and fungi.
- Pest control
- Irrigation: The vine is resistant to water shortages. This, however, does not mean that vines do not require a proper supply of water. As with any crop, the water supply program has to be adapted to its needs.