The productive period

Vines can live up to one hundred years. Nevertheless, from the point of view of producing grapes for wine-making, the life of the vine is considered as being shorter. The maximum life for a vine in the Rioja, although defined by age, is the accumulation of factors which exhaust the vine, such as:

Repeated diseases. Pruning done in such a way as to increase production. Droughts. Damage caused by machinery.

Lately, in isolated instances, we have found cases of sudden withering of Rioja vines. This occurs in vines during the ripening stage, which, apparently, have healthy roots, trunk and produce a large number of grapes. Suddenly, the green parts of the vine begin to dry up, the leaves fall and the bunches cease to ripen. The following year the vine shows no sign of life.

The productivity of the vine in the Rioja is of great interest to the enologist due, not only to the amount it produces, but to the quality of its grapes.

The enclosed chart has been prepared to show the variations in production of a vine throughout a period of one hundred years. Also for production which ranges from zero to three kilogrammes per vine. The thick broken line represents the strict production for each year and the fine dotted line expresses the tendency of each stage in the life of the vine. These tendencies are as follows:

Vine-formation stage. It spans the period from zero to four years. Productivity is negligible. Stage of increasing productivity. It spans the period from five to thirty-five years, with an increasing production per vine from 0.2 Kg to 2.7 Kg. Stage of declining productivity from thirty-five to fifty-four years. During this stage, productivity descends from 2.7 Kg to 0.75 Kg. Final stage. From fifty-four years onwards vines produce a steadily decreasing number of grapes, with levels of under 1 Kg per vine. Phases of the grape quantity produced by a red vine, according to age

Therefore, at its most profitable with regard to quantity, the vine is estimated to be about forty years old. In order to pay off the high costs of planting, attempts are made to shorten the "formation" period of the vine. But if we try to force production (as is shown by the yellow line) we also bring forward the stage of declining production; the period of productivity would only reach thirty years. However, as in so many cases, the conflict is essentially one of quality and quantity. Profitability in terms of quantity occurs during a maximum period of forty years, but better quality is attained after the twentieth year.

Another interesting piece of information is that the Control of Origin of the Rioja admits a maximum production per hectare of 6,500 Kg of grapes for red wines (48 Hl/ha). This means that any vine pruned strictly according to local practices between years 25 and 37 of its productive life, exceeds the official rate set by the Control of Origin.

Above the blue line denoting productivity stages, the climatic circumstances of each year allow fluctuations in the quantity of grapes produced by about 40%, both above and below the normal figure.

Sometimes, in order to revitalise vines of more than sixty years old the trunk is cut a short distance above the ground so that the latent buds of the old wood can give rise to a new productive structure. Thus the distance over which the sap has to flow is reduced. One of the causes for exhaustion is the progressive height of the vine trunk with the consequent difficulty for the movement of nutritive liquids.

Soils have a negligible influence on the life of a vine, although it seems that dry soils, marls, far from underground streams can, as a result of droughts, limit the life of a vine.