The root enables the vine to take up water and nutrients, necessary for growth. Most New World vineyards are irrigated whilst the converse is true of Old World vineyards. Un-irrigated vineyards means that roots grow deep in search of water and nutrients. As a result, grapes are endowed with more subtlety and depth of flavour – small roots have to typically go through the well draining pebbles that do not contain water and this prevents ‘wet and rotten feet’. They arrive at the clay for some water whilst the larger roots push through to other layers such as sand, and other kinds of soil.
In contrast, the irrigated root system is shallow and is in the shape of a tear-drop since that is where water is found from the irrigation. Proponents of irrigated vineyards affirm that their vineyards can produce better wine – especially in areas where soils such as sand and gravel hold limited amounts of water – Irrigation re-dresses nature’s shortcomings.
The trick is to ensure that the vine receives just enough water and not excess of it. Vines that receive too much water will promote ‘vigour’ or the production of long shoots, big leaves, large berries; grapes take longer to ripen. Ultimately grape quality will be compromised because the ‘goodness’ or nourishment is detoured to the production of the shoots and leaves rather than the production of grapes with flavour.
Irrigated vineyards also offer some flexibility when there is a need to increase yields. More grapes per vine can be obtained with a marginal lowering of quality in a gradual manner, since there is the ability to control water intake of the vines. With un-irrigated vineyards, increasing the yield (number of bunches obtained per vine) will lower wine quality considerably. This general rule is much influenced also by the complex interrelationships with the trellis system, the foliage on the vines, the rootstocks, the fertility of the soil – in essence the vineyard ecosystem.
One view you will hear viticulturists mention often is that ‘moderate water stress’ brings out the best in vines but too much stress can ‘break’ the vine. You can certainly draw the same conclusions when at work.
HUMAN INTERVENTION & ROOTSTOCKS
Rootstocks are part of the vine that contains the roots without the ‘trunk’, and other leafy parts of the vine. When the louse, phylloxera struck Europe, rootstocks resistant to the root louse were planted and various varieties of vines were grafted onto the rootstocks. Today, there are various kinds of rootstocks – some are chosen because they give good yields or high/low vigour in the vines, others because they are suited to soils with high quantities of certain minerals and salt or resistant to drought or other kinds of diseases.
Rootstocks provide the possibility for viticulturists to match the appropriate roots suited for the terroir, with the desired grapevine variety which originally may not have been suitable.
To graft a vine, a cut is made in the rootstock and a mirror-image cut is made in the scion (top part of the vine). Like two related jig-saw puzzle pieces, the scion is ‘grafted’ onto the rootstock. There are many kinds of grafts that can be made. Beneath is a saddle graft.