What is a legume?

Legumes, also known as Fabaceae, constitute a vast family of plants characterised by their unique ability to fix atmospheric nitrogen. Through a symbiosis with specific bacteria located in their roots (rhizobia), they convert gaseous nitrogen—unusable by most plants—into a usable form (nitrate and ammonium) for their own growth and that of neighbouring crops.

Examples of legumes

This plant family is highly diverse and includes numerous species grown for human consumption or animal feed, as well as for their agronomic benefits. Among the most common legumes are peas, beans, lentils, broad beans, lupins, lucerne (alfalfa), clover, and field beans. Each of these species possesses specific characteristics but shares this essential capacity as a natural nitrogen "factory".

The benefits of legumes in organic agriculture

In organic agriculture, legumes play an essential role. They are frequently used as cover crops or green manures to improve soil fertility without relying on synthetic fertilisers. Their action is fourfold:

• They enrich the soil with nitrogen, an essential plant nutrient.
• They add organic matter to the soil, improving its structure and water retention capacity.
• They help solubilise other fertilising nutrients present in the soil, making them more accessible to crops.
• They retain these nutrients in the topsoil layers, limiting leaching.

In viticulture, using legumes significantly reduces reliance on manufactured fertilisers, particularly in poor soils or when manure application is compromised (Source 2).

The field bean, a winter ally for our soils

At Château Cazebonne, we sow field beans (Vicia faba) in our vineyards every winter. These legumes possess proven benefits for soil health. The field bean is an excellent source of nitrogen that is incorporated into the soil by mowing and tilling it in before flowering, thereby returning the nutrients it has drawn from the air and soil (Source 1, Source 2). Furthermore, with their extensive root biomass, field beans help loosen the clay-limestone soils of our terroir. They also encourage biodiversity by providing habitat and resources for pollinating insects in the spring. In doing so, they are fully in keeping with our biodynamic approach and contribute to the vitality of the estate's ecosystems. To find out more about field bean flowers, read our dedicated article.

This meticulous work on soil revitalisation and biodiversity restoration lies at the heart of our commitment at Château Cazebonne. We passionately replant the grape varieties that had almost disappeared from Bordeaux, an endeavour made possible thanks to the continuous support of wine lovers. To explore this subject further and discover the fascinating history of our vineyard, do not hesitate to download our book on ancient grape varieties, then test your knowledge with our wine quizzes, before coming to discover our wines, reflections of our terroir and our philosophy.