Crop Load, Yield and Energy

The influence of yield, or crop load, on wine quality is one topic that a lecturer at the Waite institute – Peter Dry – strongly argued against. Although, if I recall correctly, his colleague – Patrick Illand – leant a bit the other way judging by some of his papers at least… Anyway, I feel that this old myth has some degree of truth even here in the Australian environment, although a different angle in our approach may be required!

Many factors influence the crop load of grapevines, and one of these is fruit size. Next time you get a chance, compare fruit or berries of different size, but equal ripeness. If you have a basket of strawberries, there is usually a good chance that there are at least some giant berries and some tiny ones. Which one has the most aroma and flavour? Most often, but not always of course, the smaller fruit has the greatest intensity of aroma, that at least is my personal experience. Although the total yield relates to the number and size of crop units per plant, this example still bears merit. On the number front, one basic principle in nature is that of the number of offspring (which fruit is!) and the amount of energy that the parents spend on each offspring. Just consider rabbits and humans, or mangoes vs. grass. The more offspring one has, the less energy there is to spend on each one. Thus, even a big berry, if all alone on a single vine, should be absolutely loaded with flavour..? If we then regard two vines with an equal number of berries of equal size, but with differing amounts of energy (read sugar), which one is more likely to be “nurtured” more?

The latest basic principle drawn up by Dr. Illand and Dr. Dry and co-workers, surrounds this latter idea, that the more energy a vine has to offer per crop load, the better the grape, and therefore wine, quality will be, within certain limits. This rhymes in with Richard Smart and his idea of “sunlight into wine”, although he focused very much on the sunlight actually reaching the berries, and not the leaves, where the majority of sugar (energy) synthesis (conversion rather) takes place. So, is this the final answer? Now we know what to do, so let’s go out there and bless the world with some more La Landonne and Grange Hermitage clones… Unfortunately, this isn’t the final answer. A practice whereby a grower produces little crop is not economically advantageous. A vine with little crop will divert “excess” energy into the growth of foliage (shoots and leaves), which results in shading of both berries and other leaves. Shading is a big no-no with regards to wine quality, and Dr. Smart has written a whole book on that topic. Vines in famous vineyards are often small to medium-sized and produce little crop per vine and little energy per vine. I know of no examples of great wines with fruit grown on large vines, although I’d love to see one. Thus, I don’t think we know the full answer just yet, although some strong cues are available.