The soil is a living organism that must be taken care of. Beyond the benefits of organic farming, which excludes any chemical treatment, the teams at Domaine Leflaive have generalised the practice of plant cover which alters the soil composition, the vines and ultimately the finished wines, so explains general manager Pierre Vincent.
What is the use of plant cover in the vineyard?
This is a voluntary and temporary grassing of the rows of vines by sowing a natural mixture of cereals and legumes: barley and oats; peas, field beans and vetch. We sow in September, at the end of the harvest, and a few weeks later the cover crop develops. The sole natural grass cover is irregular, hence the idea of triggering this plant cover in order to obtain greater homogeneity. We now practice it on all the plots of the estate after launching the first trials five years ago.
What effects have you been able to measure?
First, it helps to structure the soil and limit erosion: with the winter rains, good soil can slide down the plot and some terroir is lost. When we mow in April-May, there is a second effect of the plant cover: it is left to dry for a few days, to become a green manure, before burying it by light ploughing. This will bring nitrogen to the vine which it needs at this time of the year. This brings us to one of the main principles of biodynamics: you have to feed the soil, which will then feed the plant.
Does the plant cover ultimately have an impact on the quality of the wine?
Yes. It's like a third effect that will enrich the must, the grape juice. We have known for a long time in oenology that a must that is naturally richer in nitrogen will ferment better. On the contrary, alcoholic fermentation can be long or even be stopped with musts deficient in nitrogen, thus producing faulty wines: there will be sugars left, which we do not want for our dry wines, and there is a risk of premature oxidation. A balanced must also contains naturally present aromatic precursors. In the end, we will obtain more complex wines. We can thus see that the plant cover has a complete impact: pedological on the structure of the soil, agronomical on the health of the plant and oenological on the balance of the wine