|It is important to monitor water deficits and soil moisture in vineyards.
An actively growing vineyard which does not suffer from any water deficit (Photo 1) is characterised by the following traits: The growth tip is active and grows above the closest, young, unfurled leaves. The tendrils are active and the top tendril on the shoot extends above the growth tip. The leaves are perpendicular to the angle of the sun’s incidence; they are glossy and dark green in colour.
Water deficits or moisture stress in a vineyard can be divided into four stages roughly; generally you do not want a vineyard to progress beyond stage three. Remember, these observations are mostly applicable to the pre-véraison period. After véraison it is better to rely on soil moisture measurements.
The four stages of water deficit are:
The growth tip is still growing actively and the closest unfurled leaves remain below the growth tip. The leaves are still at a perpendicular angle to the incidence of the sun, but the tendrils on the bottom half of the shoot are beginning to droop.
At this stage the growth tip is less active and the closest unfurled leaves are beginning to fold around the growth tip. The tendrils that have not attached to anything are beginning to dry out from the bottom half of the shoot. The tendrils nearest the growth tip are beginning to droop. A small percentage of the leaves start turning away from the sun and tend to have a dull green sheen.
At this stage the growth tip is yellow to brown in colour and no longer growing actively. The nearest unfurled leaves envelop the growth tip entirely. The tendrils near the growth tip are drooping and detach fairly easily if touched. A bigger percentage of leaves start turning away from the sun and a small percentage of yellow leaves are present.
An actively growing vineyard
At this stage the growth tip is dead or detaches easily if touched. All tendrils that have not attached, dry out and fall off. The leaves on the bottom half of the shoot turn yellow and start falling off. The remaining leaves have a dull green colour, feel leathery to the touch and are turned away from direct sun. At this stage the shoots start showing signs of ripeness.