Julie Harrison - Soil

Publish Date
Friday, 18 August 2017, 2:35PM
By Julie Harrison

Dirt plays a huge role in wine making with soil type being a key factor in determining where the best grapes in the world are grown.  Grapes are different from many other crops as the best fruit does not come from vines grown in rich, fertile soil.  If the soil is too fertile the grape vine becomes vigorous with rampant leaf and cane growth, resulting in less energy being put into ripening the fruit.   When a vine is made to work a bit harder for nutrients you strike a balance between vine growth and berry ripening. 

Looking at some of the worlds top wine regions it becomes clear that soil has a large role to play in the quality of the resultant wines.  Grape vine roots go very deep so it’s not just what is on the surface that counts but what lies beneath.    One of the most famous soils in the wine making world is Kimmeridgian soil which is a blend of limestone and clay that is found in the southern Champagne region, Chablis and around Sancerre in the eastern Loire Valley.  Variations of free draining limestone/marl (crumbly clay mixed with limestone) soils make up the rest of Burgundy with white grapes preferring more limestone dominant soils and reds growing in soils with more marl.  Most of the Champagne region sits on chalk which is basically limestone covered with a thin topsoil.  From this you may gather that limestone is top of the pops when it comes to growing great grapes.  The key thing about soils that have a significant limestone component is that they are not particularly fertile, retain moisture well, which is great when there is a drought but also drain well in wet weather.  Vine roots can grow deep into the limestone and the calcium helps in the easy absorption of key nutrients which keeps the vine happy.

Another famous piece of grape growing land is found in Coonawarra in South Australia.  Here you find a narrow strip of Terra Rossa soil about 2km wide and around 15km long which is great for Cabernet Sauvignon. A thin top layer of fertile, rich red loamy soil around 40-100cm cm deep covers (you guessed it) a hard, chalky limestone layer sitting on top of a deep friable, softer limestone. Cabernet Sauvignon grown on this soil ripens well, is rich with cassis and mint characters, has good acidity, firm tannins and great aging potential.

Sandy soils play their part in Barolo in Italy and the North Medoc and Graves in Bordeaux. This soil type drains well and retains heat.  Wines grown on sandy soils are usually lighter in colour with elegant soft tannins and in cooler climates tend to be more aromatic.  One big advantage of sandy soils is that the insect pest Phylloxera can’t live in them, so some of the oldest vines in the world are found on this soil type as they did not have to be pulled out when Phylloxera caused havoc in Europe in the late 19th century.

Soil type defines the wines of Bordeaux.   Bordeaux is divided by its river system into the left and right bank.  The left bank soils are gravel based which suits the Cabernet Sauvignon grape whilst the right bank is clay and limestone and better suited to Merlot.  Gravel soils allow for great drainage and enable the roots to grow deep in search of nutrients meaning the vine is well balanced.  These soils retain and reflect light and heat which helps in ripening.  Across the river the best wines from St Emilion come from vineyards planted on the St Emilion limestone plateau with the Merlot grape enjoying the limestone/clay content of the soils of this region.  Neighbouring Pomerol also includes vineyards that are a mix of gravel, clay, limestone and sand which suits Cabernet Franc, however the most famous soil in Pomerol is found in a small corner of what is known as the Pomerol plateau.  Here the famous Merlot vineyards of Petrus sit on what is known as blue clay.  This is a very dense clay which the vines roots struggle to penetrate.  The resultant wine is rich, full and velvety with exceptional length and great aging potential.  Clay/limestone soils are important in Rioja and Ribera del Duero in Spain and Clay/loam soils are prevalent in the Barossa valley.  Clay is good in hot, dry climates such as the Barossa as it stays cooler and retains moisture and nutrients which is vital in periods of draught.  Wines from clay vineyards tend to be robust, concentrated and full bodied.

Arguably New Zealand’s most famous and well-defined piece of dirt is the Gimblett Gravels.  The Gimblett Gravels were part of the Ngaruroro River until 1867 when the river changed course exposing around 800 hectares of gravelly, silty land which was deemed to be wasteland.  It was only in the 1980’s that the Gimblett Gravels began to be planted in grapes but it still wasn’t until the 1990’s that planting on a large scale began.   As in Bordeaux the free draining, gravelly soils hold the daytime heat insulating the vines and helping the ripening process along.  It is not surprising then that Cabernet Sauvignon thrives on this soil type given the success of this variety in the gravelly soils of Bordeaux.   There are many other examples in New Zealand and around the world that demonstrate the importance of soil in winemaking.  Whilst the term Terroir encompasses the soil, climate and aspect of a vineyard it literally translates to “earth” in French and indeed soil type has helped define some of the world’s greatest vineyards.

About Julie

Julie and soon to be husband, Frenchman, Richard Guerra own Frog in a Barrel Wine Shop and Thirsty Frog Wine Bar in Milford. After developing an interest in wine at Massey University, Julie completed a Post Graduate Diploma in Wine Making and Viticulture at the University of Adelaide and following this worked in Australia for a number of years at Penfold Wines and Andrew Garrett Wines.  Travelling in Europe Julie developed an interest in European wines and now Richard and Julie import wine from France to sell in their shop and bar.  Julie is looking forward to sharing her knowledge of local and imported wines.

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