Factors of the Vineyard

Sometimes, understanding aspects of the complex reality behind a wine can feel cumbersome, but that should not make us give up on the attempt to understand what may bring us closer to a deeper appreciation of wines, without falling into an excess of technical terminology. In this sense, I would like to explore a series of concepts related to the vineyard, ultimately the origin of everything, that may help clarify some parameters of interest.

1. Soil water holding capacity: influencing factors
The key concept is plant available water capacity. It is not about how much water there is in the soil, but how much the vine can extract without suffering. In this regard, certain soil variables should be nuanced:

Texture: Clays have a high storage capacity, but part of the water is strongly retained and therefore unavailable. Silts, on the other hand, are optimal, though structurally unstable, and sandy soils have little reserve but respond quickly to rainfall. From a qualitative point of view, what matters most is not so much the quantity of water, but its availability.

Structure: We are interested in soils with stable aggregates, something linked to good macro and microporosity. Compaction must be avoided, as it is associated with shallow roots and early stress.

Organic matter: It acts like a sponge and improves both water retention and availability. In poor mountain soils, small differences in organic matter can greatly alter water behaviour.

Effective depth: This should not be confused with total depth, but rather refers to how far the root can grow without asphyxia or barriers such as hard limestone or compacted layers.

Stoniness: It reduces useful volume but improves drainage and thermal inertia, creating the paradox that stony soils can be more hydrologically regular.

2. Effect of soil pH on the solubility of micronutrients
pH is the great chemical conductor of the soil.

At acidic pH levels (<6), the solubility of iron, manganese, zinc and copper increases, which may lead to toxicity risks, especially manganese, and lower phosphorus availability.

At neutral pH (6 to 7), we find the optimal range for most nutrients and for microbial balance.

At basic pH (>7.5), there may be a classic iron lockup, leading to iron chlorosis, along with lower availability of zinc and manganese. The nutrient may be present, but it is not accessible.

Another concept to consider is that soil pH does not necessarily coincide with the pH of the rhizosphere. Roots may locally acidify their environment in order to solubilise iron, which is one of the plant’s strategies.

3. Role of plant hormones in the vineyard, with special attention to abscisic acid, ABA
We should think of the vine as a dynamic hormonal balance, not as a mere sum of substances. The main hormones are auxins, linked to apical growth, fruit set and the initial development of the berry; gibberellins, related to cell growth, where an excess leads to larger berries but qualitative dilution; cytokinins, which delay senescence and are linked to the balance between root and shoot; and ethylene, which is less important in the vine except in senescence and stress.

A separate chapter should be devoted to abscisic acid, ABA, the great hormone of the vine’s good judgement, synthesised mainly in the roots under water stress, in mature leaves and in berries at veraison. ABA has a series of key functions, including stomatal closure, that is, water regulation, the induction of veraison, the activation of anthocyanin synthesis and a direct connection with “good” stress. Without ABA, there is no fine phenolic ripening, only sugar accumulation.

4. Role of UV radiation in aromatic precursors
Here we are dealing with a narrow and delicate window in terms of balance. Moderate UV radiation, especially UV-B, leads to an increase in flavonols such as quercetin and myricetin, as well as greater antioxidant protection, while also stimulating aromatic precursors such as terpenes and norisoprenoids, which are important in the varieties of Castell d’Encus.

Excessive UV leads to photodegradation of aromatic compounds, sunburn, which is a defensive rather than qualitative response, harsher tannins and a possible reduction in fine varietal aromas.

Seeking balance in the vineyard, working it more like a gardening project than as a form of intensive agriculture, has a major effect.

5. Role of temperature in the aromatic precursors of grapes
Temperature has a major effect on grape metabolism, with an optimal daytime range between 20 and 30 °C and night temperatures below 15 °C. Under moderate temperatures, we increase the synthesis of terpenes, as in Albariño or Riesling, and of norisoprenoids such as β-damascenone, with significant impact also in varieties such as Chardonnay and Chenin Blanc, while supporting a good relationship between sugar, phenolics and aroma.

At high temperatures, above 35 °C, aromatic enzymatic activity decreases, precursor volatilisation is promoted, and ripening becomes disconnected from phenolic maturity. Cool nights are just as important as warm days.

6. Leaf area and grape quality
It is not a question of “the more leaves the better”, but rather which leaves, where and when. The approximate optimal index is 1 to 1.2 m² of leaf area per kilogram of grapes. Too much leaf area is linked to excessive vigour, more shade, which means fewer anthocyanins and aromas, and a humid microclimate, leading to poorer health conditions.

Too little leaf area leads to blocked ripening, excessive stress and green or simple aromas. Mature basal leaves, well lit but not burnt, are the ones that “pay for” quality.

In summary, soil, water, light, temperature and physiology must exist in creative tension, not in conflict. And this is by no means an easy task. It is a creative one, requiring a deep bond with the vineyard and living alongside it, in order to understand it and become its friend.

Raül Bobet

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Written on 01/02/2026 by Raül Bobet