Sherry wine

Climate and Soils

Olga Nikandrova and Denis Shumakov.

As is always the case with terroirs climate and soils play the key role in the Jerez region viticulture.

The Jerez Region is snugly fit into the vicinities of 36 degree of north latitude, in the area of classic Mediterranean climate (a variety of sub-tropical climate). The average annual temperature — +17,3°C. The annual rainfall — 600 mm, most of the precipitation falls in autumn and winter (simply to compare: in Pskov the average annual temperature is +5,9°C and the annual rainfall — 700 mm). Mean monthly temperature does not fall below +10°C, in July and August it approaches +25°C, average maximum — about +33°C. 173 days a year are cloudless. 63 to 75 days a year may rain. Spring frosts do occur but very rarely and may cause problems only to a small number of vineyards. Right now the weather there is approximately like this.

Summers there are not only hot, but also dry. The humidity in the Jerez Region is a complex thing. On the one hand there is a high level of evapotranspiration (evaporation and plant transpiration from land surface to atmosphere) — caused by the heat and sunshine. On the other — moist air is continuously coming from the Atlantic Ocean (Jerez de la Frontera is situated 30 km away from it, the other towns of the region, except Lebrija and Trebujena, — even closer) which doesn’t allow the area to dry up. Despite high temperature and low rainfall, there is enough moisture for the vines (droughts occur, but not very often). The ocean, of course, not only provides a pleasant level of humidity, but also smoothes out fluctuations between day and night temperatures.

There are two major geographical objects with rather different characteristics in proximity to the Jerez Region: the already mentioned Atlantic Ocean (it is mostly to the west) and Africa (to the south-east). Africa and the Atlantic have a significant influence on the Jerez Region — it is where the wind blows from.

During the seasons of the vine’s growth and ripening (spring and summer) two winds prevail in the region: Poniente (western, from the ocean, cool and humid, up to 95%) and Levante (south-eastern, from Africa, hot and dry, when humidity drops to 30%). While walking along the coastline, one can very well feel the difference between the two winds.

These are general climate characteristics of the region. There are also special characteristics which most notably manifest themselves in the climatic nuances of the Ageing Zone’s towns. Small, but essential differences of the climatic conditions in Jerez de la Frontera, El Puerto de Santa María and Sanlúcar de Barrameda become an additional factor which affects the character of sherries matured in these towns.

Of all above mentioned climate characteristics two moments are important for the vine (along with the fact that the vine can be effectively cultivated there, in the first place). First, however dry and hot summers may be in the Jerez Region there is sufficient moisture for the grape. Second, large amount of heat and sun allows the grape to ripen well and accumulate large amount of sugar in the berries.

All the rest is done first by soils, and then by people.

Albariza soil samples at Bodegas Barbadillo

The Jerez Region “in section” is gentle hills of chalky clay or marl — Albariza. Albariza (from sp. Albarizo — “whitish”, a very good word to describe the color of the soil) is special soil of the Jerez Region whose properties largely determine the specific character of the Jerez viticulture and its very interesting outcome. Sometimes (in lowlands) Albariza is covered by different types of soil — but this is not the point.

The layer of Albariza soil was formed when the area of the present Jerez Region was covered by the ocean, which determined Albariza’s mineral composition. Ideally, there should be a lot of calcium carbonate (chalk), a bit of clay and silica, and very little organic matter and nitrogen in this soil. Of course, the composition of soils a little bit differs over the Jerez Region — but the more chalk and silica are there in the soil, the better it is for growing sherry vines. The areas with more sandy and clayey soil are less appreciated.

Albariza works for the future sherry in three ways. First, it accumulates the rare in those areas moisture, thus allowing growing vineyards in general. Second, its low fertility is one of the factors limiting the yield of sherry vines. Third, its specific mineral composition provides favorable characteristics of the wine.

Due to its lamellar flaky structure Albariza easily accumulates moisture (rainwater) during winter and holds it well (in fact, it works like a several-meter-deep sponge). When it’s hot the upper layer of the soil dries up into a thick crust, which creates additional protection for the moist layer against drying. This closed-up sponge provides for a good development of the vine root system, which reaches a depth of six meters, constantly supplying it with moisture and nutrients.

The low content of organic matter and nitrogen in Albariza results in the low fertility of this soil. That is, it allows the vine to grow but doesn’t allow thriving and bearing too much fruit. This is very convenient — since to produce good wine the yield of vines often has to be artificially limited. Due to natural biological reasons the vine sets more bunches than can actually fully ripen on it. Especially so, if the soil is fertile and the climate is good. So, winegrowers reduce the quantity of the grape to promote its quality. In many wine regions the yield of wine (it is measured in hectoliter per hectare) is limited by legal regulations. In the Jerez Region the yield is stipulated at approximately 80 hl/ha.

Due to this restrictive infertility of Albariza (and to the dry climate, of course) annual formative pruning of the vines and a standard on the density of planting vines (the minimum number of vines per hectare is regulated by a special norm) are sufficient measures to artificially reduce the yield in the Jerez Region.

Finally, the mineral composition of Albariza influences the characteristics of the grape (and, in the end, sherry itself) — the effect is straightforward and convincing. Wines created from grapes grown in chalk-rich soils come out fresh, light, mineral, with low acidity (which is, however, mostly influenced by climate). Evidently, the sweeter is the sherry, the more difficult it is to discern its original freshness, lightness, and minerality. But in Fino, Manzanilla, Palo Cortado, Amontillado, and dry Oloroso these features are easily read. As well as in dry white wine produced in the Jerez Region from the Palomino grape.

Of course, sherry grape varieties may be grown not only in Albariza. In the Jerez Region itself there are two more types of soil used for growing grapes: Arenas (in coastal area, it contains less chalk) and Barros (in valleys, it is more fertile and rich in organic matter). But the main soil feature of the Jerez Region is its Albariza. And it is in this soil that all Jerez Superior vineyards (used for producing the best sherry) are situated.

The basic land division unit in the Jerez Region (as well as in all wine Spain) is Pago, there are about 300 of them; basically, they are terroirs in their nature. The quality of a pago is determined by the type of soil, altitude, land setting, exposure to the sun and wind, and remoteness from the sea. The names of best pagos are often indicated on sherry labels.

At present there are about 3500 vineyards in the Jerez Region, where mostly sherry grape varieties are grown.

Read next: Grape Varieties