2.2.3.d Implementing mulching

How thick should the mulching cover be?

To be effective, mulch must be applied at a certain thickness. Although thickeness may vary depending on the type of mulch, as a rule of thumb, a minimum thickness of 5 cm should be respected to get all the advantages mulch offers and also control weed growth.
Given that quite a thick layer is required, a large quantity of mulch grown off-site is necessary, making it difficult to apply if large areas of land are concerned.

On the other hand, there is no limit to the surface area to which endogenous mulch can be applied, as it is a protective cover that the winegrower grows and sheathes on-site between rows. It will just depend on how much mulch has been obtained. There is little information available on the use of "living" mulches under the row and the potential of certain species is still being studied.

What is the ideal timing to set-up a mulch system?

The best time to apply an exogenous mulch (one grown off-site) is towards the end of winter, before bud break and the start of the vegetative cycle, as one of the reasons for using mulch is to limit the growth of weeds.

In the case of a living mulch, for example, pilosella, the plants are first planted in small pots after harvest, in autumn or spring. Periods of frost should be avoided because pilosella is very sensitive to extreme cold. It is also difficult to sow pilosella, which makes its application rather difficult.

Like pilosella, seeds for mulching cover can be sown following harvest. The plants often germinate after the first significant fall rainfall.
In addition to limiting weed growth, mulching cover of any sort can be used to protect the soil from erosion, especially during heavy rains or on slopes with an incline of more than 5%. If this is the objective, the mulch can be applied anytime.

Is soil prepation necessary before mulching?

Depending on the mulch selected, soil preparation conditions and the application process can vary.

• In the case of a RCW or straw cover, it is best to till the soil before applying the mulch to eliminate as many weeds as possible. A soil analysis can help determine the type of mulch best suited to the soil. If the winegrower decides to apply a RCW mulch, adding fertilizer can help limit symptoms of nitrogen deficiency.

• In the case of plant cover, some measures should be followed to maximize chances of a successful germination and seedling emergence. Soil tillage and loosening is recommended before sowing. Subterranean clover, for example, should not be planted too late. The earlier the seeds are sown, the better they will take root. For this reason, sowing at harvest or just after seems ideal. As far as Pilosella is concerned, some winegrowers choose to buy pots and plant them by hand. This may be time-consuming, but the pot provides an added guarantee that the cover will work and protect the soil.

• The type of cover crop will determine the timing of its removal. For example, it is recommended to sheathe or shred Fava Beans at the end of flowering before the seed forms, which could lead to a decrease in biomass. Certain species may need to be sheathed before flowering, as lignification has not yet taken place so the plant is more fragile, making it easier to eliminate.