Reduction of the grape crop as a quality-improving measure in the vineyard, also known as thinning out, berry thinning, green pruning and green harvest, as well as French vendange vert (green harvest) or éclaircissage. The reason for this is that high yield and high grape quality are mutually exclusive. By removing grapes, an increased accumulation of various substances in the remaining grapes of the vine is achieved. The effects are an increase in extract substances, higher must weight, optimisation of the leaf-fruit ratio, higher colour intensity in red wines and better resistance to 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 during pruning, a reduction can be achieved by limiting the number of eyes to a small number. However, an extremely heavy pruning bears the risk of a drastic reduction due to bad environmental conditions during the vegetation cycle such as late frost or weak flowering. Furthermore, low pruning also results in fewer leaves on the vine. Therefore, thinning in summer is the best way to reduce yields, as many risks are already no longer relevant and expected yields are easy to estimate. A desired yield can be calculated with the following formula: average number of grapes per vine x average grape weight in kg x number of vines per ha gives the yield in kg/ha.