Soil type means different things to different people.
For those selling wine, mentioning the soil type can simply be a marketing technique to romance the product. Back labels on wine bottles are filled with this information. In other fields, sommeliers may flaunt their knowledge by mentioning the soil of a particular region.
What is often missing in the dialogue is the link about why soil is important. Why should the rest of us care?
So, here’s why it matters.
In general, the #1 most important feature of any soil type is that they provide good drainage.
The number one most important thing about soils, is that vines want good drainage. Vines don’t like to get their feet wet.
Soils with good drainage helps to increase the grape quality and more importantly the resilience of the vine during droughts. How? By forcing the roots to grow further and deeper – like waay down into the soil – the roots have access to tiny amounts of water during dry spells. As there are more root tentacles piercing the subsoil, they pick up more trace elements and nutrients along the way.
Usually, when producers are talking about soil types, they are discussing the subsoil, not the topsoil layer. If you are enrolled in a WSET wine class where you need to memorize the soil type of a region, it is the subsoil you memorize.
Old World Vineyards are not allowed to irrigate except under special allowances. This means that the soil type is far more important in Old World Vineyards than in New World vineyards where you are allowed to irrigate.
‘Old World’ vineyards refers to the wine regions of all of Europe. New World vineyards are those areas developed as a result of European colonization.
Generally, Old World producers are not allowed to irrigate the vines. This is a great advantage for mother earth as vineyards are planted in places where they get enough rainfall naturally.
Yet, not only is this a much more sustainable approach to agriculture, it has a fantastic effect on wine grape quality.
Why irrigation can possibly be bad for vines...
Those who rely on irrigation run the risk of misusing the technology. For example, vines that are frequently irrigated well, don’t need to grow into the subsoil. Instead, they may only grow roots near the surface.
But vines whose roots only grow in the immediate topsoil die quickly when water is no longer available. Furthermore, these vines also tend to be less resilient towards a whole schwack-load of other pests and diseases.
Of course, there are many techniques of controlling irrigation that lend to high grape quality.
So for most of us, knowing the soils types where the grapes are grown is superfluous.
Although to be fair, even for new wine lovers, you won’t be able to avoid hearing about wine soils. Next time you hear mention of it, ask the person why that soil type is important.
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Hillsides are great for providing good drainage
You may have also heard wine professional talk about hillside vineyards. Indeed, most of the vineyards in the Old World are planted on hills.
In France, it was the monks of the middle ages who recorded wine crop yields and quality for centuries. They were some of the first to figure out that grapes planted on hillsides made the best wine.
Today, we know why.
Did you know?
Through centuries of viticulture, monks were the first to record that hillside vineyards grew the best grapes for making high quality wine.
Hillsides drain rainfall exceptionally well; and vines don’t like to get their feet wet. Instead, the vine roots must stretch deep into the soil where they pick up trace elements and nutrients.
Yet, another reason why hillsides are great for wine grapes is because of the way they face the sun. Grapes grown in cool climates such as Champagne, just barely ripen each year. The south and south east aspects of the hillsides provide a direct route for the suns rays to ripen the grapes.
For some regions, hills provide altitude to improve quality; as for this winery here.
To grow high quality grapes, the soil type generally needs to be poor, infertile soils.
But the second most important thing about soils for vine grape growing, is perhaps that the soil should be infertile and lacking in the nutrients.
With most agricultural crops, you want fertile soils because you want to produce as many tomatoes or peppers as possible.
However, grapevines are the opposite. Vines are essentially weeds so they will grow and grow and grow anywhere. In fact, in many places in Italy and Portugal, grapevines were planted beside trees where they had an anchor to wrap around.
If a vine produces too many grapes, the quality of the juice drops.
Instead, grapevines need to fight for their existence in order to produce high quality grapes for wine. Therefore, to restrict their natural vigour and produce high quality grapes, we plant grapevines in poor infertile soils.
Conversely, grapes grown in the fertile plains along the alluvial soils left over by riverbeds, produce higher yields of lower quality grapes.
Modern viticultural techniques allow us to control vigour without planting on hillsides
Yet, planting in poor infertile soils is a generalization that more often applies to the vineyards of the Old World and even there it is still a simplified way of presenting a complex topic in one statement.
Many vineyards planted on fertile soils land can use other techniques for controlling yields and grape quality.
Fertile soil types in the valley plains near rivers produce higher yielding but lower quality grapes
The general idea is that where soils are poor, there are higher quality grapes to be picked. Where soils are fertile, as in the valley plains near rivers, they tend to be higher yielding vines growing many grapes but producing lower quality grapes that make easy-drinking, simpler wines.
This isn’t to say that all flat vineyards make poor wine – noooooo. But usually, those flat vineyards that make great wine have poor, infertile soils (think of the rocky gravel loam of Bordeaux)
I’ve also found that New World wine regions and vineyards, don’t totally follow the Old World adages of viticulture.
New World Regions instead, are the ‘Wild West’ of vine growing and are able to utilize technological advances and recent scientific research to make improvements in vine quality without following the age-old rules of viticulture.
Some soil types are warm; some are cool.
If you want to plant a vineyard, you have to be careful to choose grape varieties that will work with the soil. You also need to balance that with the climate of the area.
For example, one of the reasons why Albariño grows so well in Rías Baixes in the northwest of Spain is due to the granite subsoil.
Why does Albariño grow so well in Spain?
Rías Baixes in Spain has a mediterranean climate as the region lays right on the edges of the ocean. So it rains a lot.
On average, it rains 1600 mm per year in Rías Baixes, but some estates experience 2000 mm per year. Compare that to Alsace where it rains only 500 mm per year. Overall, grapevines only need between 300-600 mm of rainfall per year.
However, granite is a well-draining soil and this is the subsoil in Rías Baixes. To boot, these vineyards are also along the hillsides which helps rid the soils of all that excess rain.
Besides, granite is also a cool soil. Accordingly, Albariño from Spain is a premium wine partly because the grapes are able to maintain high levels of acidity because of the cool soils.
Limestone is also a cool soil. Where Merlot grows best in the world is in St. Émilion in Bordeaux which has cool, limestone soils that maintain the acidity in Merlot.
In other places, Merlot is plush with dark plum fruits and chocolate. The wines are smooth and velvety, but they cannot age in your cellar for long.
Only in St. Émilion are the soils cool enough to get the fruit ripeness in the grapes AND retain high acidity for long ageability.
On the flip side of the coin, warm soils can help ripen grapes in marginal climates.
But it's not just the quality of the grapes and wine structure that are affected by soil types. In some places, changes in the soil affect the flavour of the wine too.
If you speak with the producers in Burgundy, France, they will ALWAYS talk about the soil and the flavour of the wine in the same sentence.
That’s because small changes in the soil type change the way the wine tastes. Even when it is the same grape variety, same winemaking, same vintage, and the same producer involved.
Here is a graph of the changes in soil type on the Côte (hillside) in Burgundy.
This is a video of Edouard Labruyère, the owner at Maison Jacques Prieur in Burgundy, France. Listen to how he explains the difference between his wines – all from vineyards within the Beaune village in Burgundy.
For most people drinking wines, soil types shouldn’t really matter.
But, I’m sure wine professionals will continue to romance soils along with the wines they sell. I just wish more of them would share why those soils are important to the wine’s quality and taste.
Because some soils provide excellent drainage to ward off excess rainfall. Cool soils help grapes maintain their mouthwatering acidity, a necessary element for ageing wines. Conversely, warm soils can help ripen grapes in marginal climates. Finally, some soil types change the flavours in the wine.