Yields
The easiest way for a winemaker to make more money is to make more wine. If he can grow more grapes on the same patch of land, he will make more money from it.
The triumph of modern viticulture has been a spectacular increase in yields. Between 1950 and the early 1990s, the Australian wine industry managed to treble its production without increasing the total area of its vineyards.
Some growers can top 300 hectolitres of juice per hectare. In France, the legal limit is 90 hectolitres per hectare, not that this is always observed.
Yields and quality
It seems obvious that if the same patch of vineyard produces twice the number of grapes, the grapes will be of a lower quality.
And traditionally this has been the view. But the wine industry is very keen to convince itself that, up to a certain point, yields can be increased with impunity.
Exactly where that point is depends on whom you talk to. Not surprisingly, most people will tell you there is no point having yields any lower than their own.
Yields and natural wine
The reason conventional winemakers believe they can make good wine from high yielding vineyards is that the quality of the grapes is relatively unimportant in conventionally made wines.
Any lack of taste in the grapes can be compensated for in the winery.
A naturally made wine relies for its taste solely on the grapes from which it is made. A great natural wine, one that truly expresses its terroir, can only be made from the low-yielding vines.
For a light easy-drinking wine this means yields of 30-40 hl/h. For a vin de meditation, 8-20 hl/h.