Marl Soils: Characteristics, Properties, and Cultivations

The term “marl soils” comes from marl, a sedimentary rock composed of limestone and clay, often enriched with varying amounts of minerals and nutrients. This combination of elements gives the soil distinctive characteristics and directly influences the quality of the crops. Found in many regions worldwide, marl soils provide a suitable habitat for vine cultivation. Their balanced mineral content and complexity promote the growth of high-quality grapes, which produce elegant and long-lasting wines.

Marl soils were formed millions of years ago, between the Cretaceous and Paleocene periods, when limestone and clay sediments accumulated on the seabed. Over time, pressure and geological processes compacted these deposits, transforming them into marl, a layered rock rich in minerals.

In hilly areas like Valpolicella, tectonic uplift and erosion have shaped the landscape, bringing these fertile soils to the surface, making them ideal for viticulture. The proportion of limestone to clay in the marl varies from one area to another, affecting the soil’s ability to retain water and release minerals—key elements that define the structure and aromatic profile of wines in different production zones.

Widespread all over the world, marl soils make up the soil of many of the most renowned and appreciated wine regions, from Burgundy and Champagne in France, to Rioja in Spain, and Napa Valley in California.
In Italy, they are present in Piedmont, particularly in the Langhe area, where they contribute to the elegance and longevity of wines like Barolo and Barbaresco; in Tuscany, where they characterize great reds like Brunello and Chianti; and in Sicily, where they influence the structure and complexity of the famous Nero d’Avola.
In Valpolicella, these soils are essential for the production of Valpolicella and Amarone, ensuring balance, complexity, and a distinctive aromatic profile.

Marl soils are distinguished by a fine and compact texture, with a variable composition of limestone and clay. These characteristics ensure a good balance between drainage and the ability to retain moisture and nutrients—key qualities for viticulture, especially in hot climates. The pH tends to be alkaline, ranging from 7.5 to 8.5, while the presence of minerals such as calcium and magnesium contributes to the structure and aromatic profile of the wines. The light color of the marl reflects sunlight (the albedo effect), helping to keep the vines cooler, while organic carbon helps preserve soil biodiversity. Beneath the surface, microbiological activity is intense: earthworms, insects, and mycorrhizae—symbiotic fungi that improve nutrient absorption—enrich the soil, making it fertile.

This soil type can vary in their structure and organic composition: in Arbizzano, in the Valpolicella Classica area, limestone-rich marls prevail, ideal for cultivating native varieties like Corvina, Corvinone, and Rondinella, from which important wines like Amarone are made. In Colognola ai Colli, in the Valpolicella Orientale, clay-rich marls are found, rich in nutrients and perfect for Garganega, the grape variety used to produce Soave.

Marl soils are classified into different types based on their mineral composition and pedoclimatic conditions. The combination of limestone and clay, in varying proportions, directly influences vine growth and the wine profile.

• Limestone-rich marl soils: these marls, rich in limestone (calcium carbonate), promote drainage and impart elegance, complexity, minerality, and longevity to the wines. They are typical of hilly areas, where the vine develops deep roots.
• Clay-rich marl soils: with a higher percentage of clay, these soils retain moisture and nutrients, promoting the production of structured and intense wines with soft, well-integrated tannins.
• Sandy marl soils: characterized by a light texture and excellent drainage, they retain fewer nutrients but favor the production of fresh, aromatic wines with pronounced minerality.

This variety of marl soils is particularly evident in wine regions such as Valpolicella, where the differences in soil composition allow for wines with unique organoleptic nuances, from the intensity of Amarone to the freshness of Valpolicella Superiore.

The main advantages of these soils in viticulture include:

✔ Excellent water retention, useful during dry periods.
✔ Mineral richness, which adds greater aromatic complexity to the wines.
✔ Balance between drainage and fertility, preventing water stagnation.

However, marl soils also present some challenges:

✘ Tendency to compact, which can limit root development.
✘ Difficulty in working the soil, especially under high humidity conditions.
✘ Possible excess of limestone, which can reduce the vine’s ability to absorb certain nutrients.

Thanks to their balanced composition, marl soils are suitable for various crops, including olive trees, fruit trees such as cherries and almonds, as well as cereals and legumes, which benefit from the good drainage and mineral richness of the soil. However, the vine remains the most widespread and characteristic crop for these soils, which allow each variety to express its aromatic characteristics to the fullest.

Although marl soils are particularly suitable for viticulture, they require careful management to make the most of their potential. They tend to compact, hindering root expansion, and may retain excessive moisture during heavy rainfall. Additionally, active limestone can promote iron chlorosis, while the alkaline pH can reduce the availability of essential nutrients.

To address these challenges, at Tenuta Santa Maria di Gaetano Bertani, targeted agronomic techniques are employed: the use of organic amendments, such as composted manure, enriches the soil, while surface tilling helps maintain a looser structure, preventing compaction. Controlled irrigation allows balanced moisture management, avoiding both water stagnation and drought stress.

Attention to biodiversity guides our choice of integrated and sustainable viticulture: the adoption of the Guyot training system promotes superior grape quality and a richer bouquet, while cover cropping between the rows protects the soil from erosion and supports the fauna. This approach, combining tradition and innovation, allows us to produce wines that fully express the unique character of the Valpolicella terroir.

Valpolicella, with its marl soils, boasts a unique geological formation that must be preserved and enhanced. These soils are naturally fertile and ideal for viticulture, offering excellent water retention to combat drought while ensuring optimal drainage. Although they pose certain challenges, such as compaction or iron chlorosis, their future is filled with opportunities. Through sustainable and regenerative techniques, marl soils will continue to produce wines with extraordinary aromas and complexity, like those crafted at Tenuta Santa Maria.

Every glass of our Amarone della Valpolicella Classico Riserva or Lepiga Soave reflects our dedication to the soil of Arbizzano and Colognola ai Colli. While climate challenges persist, opportunities abound: we firmly believe that when treated with respect, these soils will remain a valuable asset and a defining element of both local wine and agriculture.

Between Valpolicella Classica and the Soave area, Tenuta Santa Maria di Gaetano Bertani is proof that a cherished land always responds with generosity, offering an explosion of aromas and flavors for wines that are both intense and refined.