Jamie Goode: Yields – is less always more?

There was a time when knocking the mantra that lower yields result in better quality was all the rage in wine science circles. With most crops, yield is everything. The more you can grow, the better you are doing. With wine, it’s quite different. First of all, people try to avoid fertile soils for winegrowing, instead wanting the vines to struggle a bit (but not too much) so that rather than focus on growing lush canopies, they should put their energy into growing grapes. And firmly established in most appellation laws in the classic European wine regions is the notion that higher yields result in grapes that make less interesting wine. So typically the rules will specify a maximum yield for each appellation expressed in hectolitres per hectare. And in any one region where there is a hierarchy of appellations, the increasing quality comes with a reduced maximum yield. Those from non-European regions might well be sceptical of this idea that there is some causation, or even a tight correlation between lowered yield and better quality, especially when you have a situation like that found in Champagne where there’s a maximum yield, but growers produce more in many years and then are allowed to use this excess for creating stocks of reserve wines. If growing higher yields significantly reduced quality, then why would growers target over the legal yield? Would they really want to compromise quality like this? So clearly in some regions a maximum yield is imposed in order to game the market and keep demand high. But this doesn’t mean that all yield restrictions are bad.

 As a result, the notion that there’s a tight correlation between yield and quality has been questioned. One popular idea was that bigger canopies allow the ripening of larger crops, and so opting for split canopy systems with much higher photosynthetic capacity would allow the vine to carry bigger crops and still achieve high quality.

In his book, Terroir and other myths of Winegrowing, Professor Mark Matthews had this yield/quality idea in his cross hairs. One of the ‘myths’ he highlights is what he calls HYLQ (‘high yield low quality’). He takes a thorough look, and explores the ancient history of this concept, as well as examining what wine writers and critics have said about yield. But when it comes to the science, the literature has a whole bunch of studies that aren’t really going to be able to answer the question for fine or interesting wine because of the vineyards they were done on, or the read-out of the experiments. He’s put together a convincing argument from what’s available in the scientific literature, but he might have spent his time better visiting vineyards around the world where winegrowers are making really interesting wines, and they know that if they don’t restrict yield, their wines will be less interesting. Matthews must assume they are daft enough to cling to old traditions even though it will be costing them a lot of money. I’ve met many of them, and they aren’t daft, and they aren’t afraid to question tradition. But where Matthews is correct is in pointing out that there is no simple relationship between yield and quality: this is surely a nuanced subject.

So let’s have a look at the science of yields and quality. One issue that needs to be addressed straight away is how are we measuring yield? Is it tonnes of grapes per acre/hectare? Or yield per vine? Then planting density is important. And there are no universals here: a lot will depend on the region.

If you are doing experiments in California’s hot, irrigated Central Valley, with dust-mulched vineyards, normally farming with heroic yields, then there’s a good chance you could drop yields and see no increase in quality. Same grows for the hot bulk wine regions in Australia, or the lower quality terroirs in Bordeaux. Do what you like in a horrible vineyard set up for bulk wine production and you won’t see much in the way of a quality up-tick with lower yields.

Let’s consider yield per acre/hectare. Lower yield clearly doesn’t always result in better quality. You might have missing vines and high disease pressure, and have lost yield because of poor viticulture. This isn’t going to increase quality.

And a lot depends on the starting point. You might have a very well balanced old-vine vineyard giving good yields. In this case, there may be no point in dropping crop. If you do, you might bring harvest forward, and in warm climates, this may be problematic because the grapes are ripening in summer conditions rather than autumnal ones. This might be a negative. Lower yields might result in riper fruit, and in some cases over-ripeness.

In other settings, you might be looking at a bumper harvest, but one that the vines won’t be able to ripen before the growing season runs out of oomph. Sometimes, dropping crop is the only way to get the remaining grapes ripe enough. I remember spending time in Marlborough and hearing stories that with harvest not too far off, many of the vines were carrying crop loads as high as 35-40 tonnes per hectare. Marlborough gets good yields of Sauvignon – the average is around 16 tonnes/hectare, and some Dillons Point vineyards can give 20 tonnes/hectare at top quality – but the vines simply wouldn’t be able to ripen 35 tonnes/hectare and so growers were running machine harvesters down rows to do some crop thinning.

One piece of evidence in favour of the lower yields raising quality argument is that people do drop crop in many regions around the world. If there was no quality gain to be had, then this would be counter-productive, because it costs money to reduce yields. Either people are doing it for a reason, or they are stupid. People who are stupid like this usually go out of business. People would laugh at scientists suggesting there isn’t a relationship, because they have often experienced what happens with higher yields, and for top quality wine it just doesn’t work. They know that there’s a limit to what their vineyards can produce before the quality starts going down. But these are often vineyards with potential for top quality. Some sites can’t reach top quality irrespective of yield.

Nature sometimes intervenes and does its own experiments on yield and quality for the growers. I’ve tasted Pinot Noirs from New Zealand and California where the crop has been reduced far below the winegrowers choice through frost or hail events. The surviving grapes end up making small quantities of concentrated, intense wine. Sometimes the structure and intensity is a little too much, but these naturally low yielding vintages can be very instructive.

And then we have old vineyards, where often there is a reduction in yield. Is this part of the benefit of old vines? It’s difficult to say: sometimes the yield is reduced because there are missing vines, or there’s some sort of disease. Perhaps the advantage of old vines is that they have a natural balance. Given good farming and wise pruning, there’s no reason why old vines should have considerably lower yields than young ones, and I suspect that you could get great quality with reasonable yields from a healthy, well-farmed old vineyard.

This is clearly not a simple topic. Growers should be cautious in assuming that lowering yield is going to give them better quality. It all depends what you mean by quality. It also depends on the vineyard region, the site, the existing yield, the health of the vines and the stage that yield reduction is practised, as well as the vintage conditions (which you won’t know in advance). The best thing is to read the vintage, and do some trials, and see what works.

• Jamie Goode is a London-based wine writer, lecturer, wine judge and book author. With a PhD in plant biology, he worked as a science editor, before starting wineanorak.com, one of the world’s most popular wine websites.