2.2.4.g Establishing the grass cover

When is the best time to sow?

Sown grass should ideally be planted in autumn, as soon as possible after harvest. However, grass can be sown in some coastal or northern vineyards in springtime. It depends on the climate but also on the species chosen. That said, the weather forecast should be monitored whatever time of year to avoid planting in heavy rainfall. This could cause the formation of a soil crust which prevents the young seedlings from germinating and breaking through the soil, or even leads to root asphyxia in the young shoots. Some species are also sensitive to frost.

How to sow?

Several sowing techniques exist but initially, a shallow tillage is recommended to prepare for planting. The aim is to create a seedbed of a few centimeters that has flattened soil without any clumps of earth, as these would prevent the seedlings from breaking through. This can be carried out with implements such as a ploughing claw and/or comb. Once this preparatory work is done, the seeds can be broadcast or sown in lines. There is also a variety of commercial seeders, generally composed of a container (hopper) that can hold up to a hundred liters placed on several rows of discs and teeth. The width of the seeder is adjustable so it can be adapted to the width of the vines.

How to properly maintain a grass cover?

How to manage plant height?

Plant height should be managed to avoid the risk of spring frosts and/or the growth of fungi, which, in humid microclimates, encourage cryptogamic disease outbreaks. To do this, the plants can be either mowed or rolled. While mowing cuts the plants, rollers flatten the cover crop by constricting the sap flow. With the flow of sap restricted, competition for water between the vine and the grass cover is limited, unlike mowing. Rollers can be used on lignified plants or species with hollow stems. Several types of rollers exist and are chosen for their specific characteristics.
See section on Green Manure

What is the best or worst time to mow?

Mowing is generally done towards winter's end though before budburst to limit spring frost risks.
The mowing frequency will depend in part on the plant cover's growth rate. It will also depend on the weather conditions, especially if the spring is wet and cold. In general, 3 to 4 mowing sessions are necessary to correctly maintain the grass cover.

Several tools mounted on agricultural machines can be used to mow grass, such as hammer mills or vertical shaft mowers. Inter-cep mowers are used to mow between the vines.
New robotic tools are being developed specifically for vineyard mowing. They consist of small autonomous robots that move around the vineyard to mow the inter-row and/or between the vines.

How to maintain a grass cover in the long-term?

Is alternating plant species necessary?

Different species can be interspersed when renewing the cover crop. The species choosen for this renewal should be selected according to the same critera used for the initial establishment of the grass cover. Consequently, the choice is determined by, amongst others, the soil characteristics, if the variety possesses particularly sought-after characteristics and the plot's vigor. Renewal of the grass cover with additional varieties of plant species also contributes to increasing biodiversity in the vineyard.

How often should the existing cover crop be destroyed to work the soil?

The durability of the grass cover will depend on the species chosen. A rough guideline is to keep the grass in place for 5 years, but this can be extended to 8-10 years, if the grass is in good condition.
When the grass cover is planted on 1 row out of 2 or 3, it can be renewed on one of the bare rows. In subsequent years the grass cover can rotate with the grassed row becoming bare and the bare row planted to grass. This reduces compaction caused by tractors repeatedly driving through the weeded row.