The yield control is the topic of many – sometimes heated – discussions between wine-makers and even between wine consumers.
Nowadays hardly anybody questions that high-quality wines come from low-yielding sites. In fact some of the most celebrated wines come from some of the lowest-yielding vineyards. But we cannot extrapolate that a lower yield produces automatically higher quality wine. Reducing crop level by pruning or by fruit thinning does not automatically increase the quality or market value of a wine. It might sound strange for many, but it can actually have the opposite effect.
Reducing crop level on a vineyard that is on fertile soil and is pumped up with nitrogen and irrigation will only create an under-cropped vineyard. The fruit will accumulate sugar rapidly and become “sugar ripe” well before acids and flavors reach their potential and that might not be what the wine-makes and the consumers want.
Quality, by the way, is not really definable, but studies of wine quality generally use intensity of color, aroma, flavor to indicate quality. Some like the less intense style and others prefer thick, oily and very intensive wines.
Clearly, yield versus quality is definitely site and grape specific and grape type relationship, and there is no universal model of yield to quality. The relationship between crop level and sugar accumulation is that the lower the crop, the faster the sugar accumulation. Of course it is true only within a range because the sugar production from the leaves is limited. Further reductions in crop level beyond that limit will not result in faster sugar accumulation.
Sure, that is only the story of the sugar and we all know that ripeness and fruit quality is not only about sugar. The acids, aroma and flavor constituents of the grape as factors that influence wine quality. Not surprisingly none of these comes from the leaves. The grape berry is autonomous with respect to aroma, flavor and acid development, receiving only water, minerals, sugar, organic acids and amino acids from the parent vine. The berry makes the other stuff from those raw materials.
rt is quite likely that there is more infrastructure or there are more enzymes to support the ripening process present in each berry at lower crop levels. Maybe there is a ripening signal, a hormone, that is stronger when less fruit is hanging on a vine. Or just simple it’s that there are more raw materials (organic and amino acids) available for the fruit when there is a lower crop load. Some of these are speculations yet to be proven. But there are hard facts as well.
At lower yield the fruit clusters are less dense and so they get more air, more sun and that definitely helps the development of aromas, acids and flavors. Also it is known that fruiting is a stress for the vine, that means reduction or removal of fruit during ripening has been found to reduce the rate of photosynthesis in thed leaves and to reduce the conductance of the vines. So vineyards with lower crop levels can be farmed with less water and fertilizers. Many of the lowest-yielding vineyards are also non-irrigated or are irrigated sparingly.
After considering all the information we have available, we decided that we put our vote on the low yield technology. The reason was and still is that our goal is to produce intense wines with rich aromas and robust character in order to express the terroir of Somló and we are ready to make compromise on quantity side for this goal.
Of course yield control means different thing with different vines. On the juhfark and hárslevelű we grow about 1kg fruits and on the furmint slightly less. On the other hand the traminer gives the best at about 1.5kg yield.