2.2.2.b Different tools and their application

Tillage under the row

Hilling-up

Tillage directly beneath the vines consists of hilling-up. This involves forming a mound of earth around the base of the vines. It can be carried out directly after the harvests to protect the vines from cold temperatures during the winter. It is then a very effective means of weed control in the spring through to the end of the growing season, with alternate hilling-up and de-hilling. This practice is fairly fast and can be done at around 7 km/h. It requires the use of ploughshares or notched discs that can be inclined.

Dehilling

Once the winter is over, the vines can be de-hilled. This process removes the mound of earth that was built up around the vines in the autumn. De-hilling is generally carried out at the beginning of the growth period, prior to budburst, because the risk of frost increases for between 2 and 5 days after tillage. By loosening the soil, aeration can cause water evaporation which leads to a further drop in the external temperature for the upper layer of soil. Moreover, loose and/or dry soil is not as efficient at conducting heat, so there is a greater risk of frost damage. It is therefore important to avoid loosening the soil, even slightly, when a severe frost is forecast. Hilling and de-hilling also control weeds mechanically. The type of tool depends on cover crop height, if weeds are present and the type of soil.

• De-hilling machines are rather slow, with a speed of 2-3 km/h. They are effective weeding tools as they turn the weeds over and expose their roots. However, there is a risk of damaging the roots of the vines near the surface and displacing a considerable quantity of soil.

• Rotary and other types of mechanical hoe are very practical. Their weed-control action is intense, and so they need soil with a good bearing capacity and no coarse elements, as they can project stones between the rows and damage the vines. It is not advisable to use this tool with perennials that disperse easily, as it combines cutting, uprooting, and dispersing. Their speed is usually limited to around 3 km/h.

• Between vine hoeing or weeding blades have an enhanced weeding action as they cut the weeds' roots. There is relatively little soil displacement, so plants may recover in wet conditions. Faster than other tools, they can operate at a speed of up to 5 km/h.

Inter-row tillage

Decompacting and loosening of the soil

The soil in vineyards can become compacted for several reasons, such as deep ploughing during uprooting and the working of a plot, the formation of hardpan after driving over insufficiently dry ground, the repeated passage of agricultural machinery or sudden, heavy rain which can cause a compacted layer of soil to form at the surface. Whatever the reason, it is important to aerate the soil by reducing these compaction phenomena which can have serious consequences:

• Soil and root asphyxiation and reduced microbial life
• Poor penetration of water and fertilizer, increased leaching of the latter, erosion
• A decrease in deep root exploration, a primarily surface development and a greater risk of breakage when tilling the soil under the row
• Greater sensitivity to water stress and parasite attacks, a decrease in yield and quality potential, withering and general decline in severe cases.

The primary role of soil decompaction and loosening is to improve water absorption and drainage by aerating the soil. It can be done in a preventive way by reducing the number of tractor passes or by grassing, but some agricultural machinery is specially designed for this:

• Soil decompaction can be done with decompactors, a type of tool with deep tines that penetrate the soil to a depth of between 20 and 40 cm. They create break lines by fracturing and/or breaking up the deeper layers, but they do not enable organic matter to be buried.

• Heavier decompacting tools exist, notably subsoilers. These are also tools with deeper tines, which allow hardpan or ferruginous layers to be broken up. These tools can go down to a depth of 70 cm and are mainly used to decompact bare plots.
  Whatever the tool used for decompaction, it is important to work with well-dried soil and not overuse this practice which also destroys macropore structure and can contribute to a weakening of the soil structure. Before any decompaction work, it is necessary to establish the decompacting sequence, not to decompact all the rows, not to go too close to the vines and to take into account all the plot's characteristics. The higher the decompaction speed, the more effective it is.

**Shallow ploughing, scarifying and levelling of the soil

Throughout the growth period and up to the harvests, whether the vineyard is grassed or not, the soil should be tilled frequently. Very shallow ploughing or scarifying is generally used to aerate and loosen the soil and uproot weeds or grass. Tools equipped with claws can also be equipped with "combs" to smooth the soil after the passage of the claws. Rotavators, rotary harrows, rollers and shredders can also pack down the soil and pinch out weeds.