Vineyards and Irrigation
Wine made from vineyards that have been irrigated tends to be different from that from vineyards wholly dependent on the natural rainfall of the region. This is obvious: the water plumps out the grapes just as they need sufficient moisture – whether taken in from the foliage or via the roots – in order to fill out. Too much water may affect their content and result in a lack of certain elements essential to making good wine. The matter is complex and need not concern the ordinary drinker very much, especially as regards European wines, because the majority of these are made in vineyards where irrigation is not only unnecessary, but forbidden; and where the rainfall in nearly all years is adequate. Irrigation is now allowed in some German vineyards.
In many of the vineyards of the New World, however, irrigation is not only permitted but essential: in some of these vineyards, the micro-climates are such that parts of one vineyard might be unable to produce grapes in good condition without irrigation, both because of the dryness of the atmosphere and because of the absence of water in the subsoil. In addition, the irrigation of some patches of vineyard is necessitated by the circumstance of sections of subsoil being thick clay, which would either retain any naturally falling water too much – so that the vine roots would risk rotting – or being so porous that the water falling on the vineyard would drain away too rapidly to be absorbed by the vine roots. So many large New World vineyards make wines which are the produce of a vineyard wherein parts may be irrigated and parts not. It has been pertinently remarked that some classic wine grapes, in New World vineyards that are irrigated, actually get less water than they would do naturally in some better-known European vineyards!
The intricacy of the matter is great, because water falling on to a vineyard will come from a different source from that draining through the subsoil. Therefore water used for irrigation must be suitable for the purpose – not just wet. There are also different methods of irrigating: the spray method, whereby a fine mist of water is directed over the whole vine or row of vines; and the drip method, whereby a pipe laid alongside the vine roots slowly drips moisture into the soil. The particular portion of vineyard, the grapes and the exigencies of the climate all affect the way in which irrigation is used and the extent to which a wise winemaker will adapt it to his needs, without risking a fall in the quality of the eventual wine. The hazards of winemaking seem to indicate that judicious irrigation can be as beneficial as judicious chaptalisation.