For a living soil: vegetative cover at our Family Estates.
Les efforts environnementaux sont au cœur des préoccupations de la famille Castel sur leurs vingt propriétés à travers la France.
Inspired by a virtuous philosophy, Technical Director Cédric Pla and the teams at each château have worked hard to reduce inputs, focussing on intelligent soil tillage, to serve the quality of the wines and the sustainability of the winemaking process.
“The basic aim is to bring life to the soils”, exclaims Cédric Pla, “because a living soil hosts the organic matter and returns it to the vines.” Replacing chemical treatments, the Technical Director, as well as the property managers and their teams have redoubled their efforts, focussing on innovative techniques. They have worked hard to develop mechanical tillage, with the ultimate aim of covering 100% of the surfaces, and eradicating herbicides. Protecting biodiversity has become a daily concern, via a new approach to vegetative cover, using carefully selected seedlings.
Encouraging biodiversity
“Historically, in Bordeaux, prioritising the “tidiness” of the vineyard, winemakers weeded the entire surface,” recalls Ludovic Hérault, property manager at Château Montlabert. “Today, practises have evolved, and it has become clear that the former approach left the soils vulnerable to erosion. At Château Montlabert, we haven’t used herbicides since 2011.” While natural vegetative cover has been used for a long time as a means to encourage soil life, the downside of such methods was that they tended to provide unwanted competition for the vines, relying on the same nutritive elements in order to grow. To avoid this scenario, vegetative cover is planted between the rows of vines, prioritising low growing seedlings, frequently covering every two rows. This is the case at Château Montlabert, although covers may also be installed on two rows out of every three.
Bringing life to the soil from september to spring, vegetative covers capture and store atmospheric nitrogen, which is later returned to the soil when the seedlings are ground, cut, or buried in the soil. Easily trimmed, tractor use and therefore soil compression remains minimal, preserving soil life. “As such, the macro and micro-organisms present in the soil break down these natural fertilisers. The biomass mineralises organic matter, providing the vines with the organic material that they need in order to grow,” explains Cédric Pla.
This environmentally virtuous approach also makes financial sense. The savings made as a result of the reduction in inputs are reinvested in the human and material resources that are indispensable as part of an effective soil-management strategy. Extra tools have been acquired, including the specially adapted inter-plant ploughs that enable the required five to eight passages, rather than the two that were needed when chemical herbicides were used. As Cédric Pla indicates, “We till the soil as precisely as possible, selecting tools based on the soil type, the time of year, and the weather conditions.”
In order to limit the amounts of greenhouse gases produced by mechanical tillage, electric high-clearance self-driving tractors (“Bacchus” and “Ted”) are currently being tested. The vineyards at Chateau Montlabert and Château du Lort have been mapped and prepared to welcome the vehicles.
100% natural fertilisersAlongside the eradication of chemical fertilisers, large-scale tests were been carried out last year at the Bordeaux Family Estates Château Montlabert, Château de Haut Coulon and Château de Goëlane to prioritise the use of natural fertilisers, via a system adapted to each plot of vines. “All the seedlings we use have a specific role, but each of them allows us to enrich the soil,” explains Ludovic Hérault. A selection of plants has enabled the Family Estates teams to gradually adapt to the new approach, according to the specific properties of each type of terroir.
For example, leguminous plants are prioritised in plots where the vines grow less vigorously. Oats, vetch, fava beans and forest rye are used to reinforce the soil’s structure, as well as to enrich it with nitrogen. Barley is active against weeds, including quackgrass. “On one particular plot of the Château Barreyres vineyard, we were faced with a number of blocks of highly compacted sediments which were very difficult to break down and led to significant water retention on the surface of the soil,” explains Cédric Pla. “In order to break down or pierce these blocks, we planted mustard.”
Tests have also been carried out using subterranean clover, “a variety that does not climb the vines, but covers the soil like a carpet. As such, the clover competes for nutrients with weeds. Another advantage is that it spreads year on year spontaneously.” Its multiple advantages are fully showcased at Château de Haut-Coulon, a terroir that has always been sensitive to problems linked to erosion, and presents the unusual challenge of a 30% slope. The vineyard’s topography limits tractor access during periods of heavy rain, making tillage virtually impossible at certain parts of the vineyard. The subterranean clover reinforces the structure of the soil and limits erosion, without providing unwanted competition for the vines. One of the beneficial side effects of this approach has been to reduce our reliance on tractors, and so to reduce our overall carbon emissions,” she says.
Cleansing the soil
“Agriculture is becoming increasingly technological and scientific, and we need to make sure that the progress made is beneficial to life and nature. Agricultural production must try to be as virtuous and self-sufficient as possible,” recalls Cédric Pla. Aiming for constant progress, the Family Estates technical team is continually looking to optimise its approach to research and development. With this in mind, Léa Mazubert, head of research and development, became the latest addition to the technical team, with the objective of bringing together ecological and economic performance.
One such ongoing test involves an attempt to remove traces of copper-based treatments, which are among the most widely used in organic winegrowing, and are known to remain present in the soil without degrading. As well as mapping the presence of copper residue in the soils, Château Montlabert is currently testing a solution designed to remove residues from the soil by planting carefully selected vegetation, including marigolds. “These flowers capture the copper through their roots. The metal then passes through the flowers,” explains Léa Mazubert. "After that, the marigolds are removed, and we work with a start-up who are able then to extract the copper from the above-ground parts of the flowers. The copper can then be reformed and re-used.” To measure the efficiency of these efforts, a surprising test is carried out each year at Château du Lort. Cotton underwear is buried in the soil, with the extent of its deterioration over a certain period of time providing proof of a rich, living soil.
All of the Castel Family Estates have been certified Terra Vitis since at least the 2019 vintage, except Château de Haut Coulon (in organic conversion) and Clos des Orfeuilles (certified organic). Many have long-standing commitments to environmental approaches, such as Château Montlabert in Bordeaux and Domaine de la Clapière in the Pays d’Oc. Today, the structure of the Family Estates enables them to share their experiences with other properties, which may have gained environmental certifications more recently. In the same way, via the Terra Vitis certification, each of the Family Estates benefits from the Déphy nework, which aims to Demonstrate, Experiment and Produce studies on systems based on low Phytosanitary input.
