Reduction of the grapes as a quality-improving measure in the vineyard, which is also referred to as thinning, curtain thinning, green cutting and green harvesting as well as French Vendange vert (green harvest) or éclaircissage. The reason is that it is higher earnings and high quality grapes are mutually exclusive. By removing grapes, an increased accumulation of different substances in the remaining grapes of the vine achieved. The effects are higher extract levels, higher Mostgewicht, Optimization of the leaf-fruit ratio, higher color intensity with red wines and better resistance when drought. Apart from the general increase in quality, a positive long-term effect can be achieved, especially with young plants, because they can develop much better.
Already with pruning can be limited to a small number of eyes achieve a reduction. However, an extremely strong bleed carries the risk that poor environmental conditions during the growth cycle like late frost or weak blossom there is a drastic reduction. Furthermore, the vine has fewer leaves with a small first cut. That is why thinning out in the summer is the best way to reduce yields, since many risks are no longer relevant and the expected yields can be estimated well. A desired yield can be calculated using the following formula: average number of grapes per stick x average grape weight in kg x number of sticks per ha gives the yield in kg / ha.
The optimal time for thinning is quite different depending on the desired result. This can be done as early as possible when the berries have reached pea size. However, there is no significant reduction in earnings. Ideally, the beginning of the ripening period or veraison, because then a necessary differentiation between ripe and less ripe grapes is clearly visible. This is usually the period from late July to early August. The targeted removal of grapes with ripening residues works best. As a rule, these are the highest grapes on the vine. A common form is leaving the bottom grape pro shoot, Up to 50% of the grape mass is removed.
As a rule of thumb, 50% fewer grapes "only" result in a 25 to 40% reduction in yield. In the past, the green grapes were often left on the ground and served as compost, This is rarely practiced today, to a degree pollution (Contamination) with microorganisms to prevent. The removed grapes are also increasingly used for the production of Verjus (Juice of unripe grapes). Growth regulators are an alternative to manual thinning gibberellins (Plant hormones) used. Other forms of yield reduction include: grapes break respectively. grapes division by halving the grapes. The video (click to view) shows the thinning at the Mario J. Burkhart winery in the municipality of Malterdingen (Breisgau area in the growing region to bathe ). See also other measures below Weingarten Care,
Pictures: Winery Mario J. Burkhart