Vine balance

Yield figures are what appellations publish and what arguments are conducted in, and they are a poor proxy for the thing that actually matters.

The same tonnage per hectare means entirely different things at 2,000 vines per hectare and at 10,000.

Ripening requires photosynthate, which comes from leaves. Researchers use ratios of leaf area to fruit weight as a working guide, and vines below the threshold ripen slowly or incompletely.

Excess vigour is the opposite failure. A vine with abundant water and nitrogen puts energy into shoots and leaves, producing a dense shaded canopy that ripens fruit poorly, retains methoxypyrazines and holds humidity that favours disease.

The Ravaz index — the ratio of crop weight to pruning weight — is a standard field measure of balance, and it is assessed after the fact rather than predicted.

Balance is managed through several levers at once: pruning severity sets bud numbers, shoot and bunch thinning adjust crop, canopy work sets exposed leaf area, and rootstock and water management govern vigour.

Site does much of the work. A low-fertility, free-draining site imposes balance naturally, which is a substantial part of why such sites are prized.

It converts "low yields make better wine" from a slogan into a testable claim — and shows why the slogan is right about overcropped vines and wrong as a general rule.