Sheep grazing in vineyards
Grazing of grass-covered vineyards has a dual interest, both for the farmer and the winemaker.
Grass cover management
To successfully graze vineyards it is essential to properly manage the grass cover.
Estimation of grass production
The standing grass production depends on its height and density. INRAe indicates that there are 100 kg of dry matter per centimeter of grass height per hectare available for grazing. Thus, a height of 10 cm corresponds to 1 T of DM/ha.
However, it should be noted that the nutritional value of pastures or grass-covered vineyards decreases as the grass matures. For example, at the 10 cm ear stage, a permanent pasture has a nutritional value of 0.90 UF (Forage Unit)/Kg of dry matter (DM) and 16.7% nitrogen content (MAT), which corresponds to good hay. At the early heading stage, it is only 0.83 UF/Kg DM and 13% MAT. At flowering, the value drops to 0.6 UF/Kg DM and 9% MAT.
It is therefore essential to have good grass cover in the vineyards and to bring the animals in when the grass height is good, between 7 cm minimum and 20 cm maximum. The height of the hocks is a good indicator.
Practices to avoid for good vineyard grass cover
Overgrazing
Overgrazing, generally due to too long a grazing period in the same place or overstocking of the plot, can have several harmful impacts:
- Increase (x3 to x4) the regeneration time of the vegetation cover, except during the period from late autumn to mid-winter when it is less problematic to graze low.
- Risk that the sheep turn to the vine, once all the grass is eaten.
- Increase the risk of parasite infestation.
- Damage the root system of plants and thus the longevity of the grasses in the vineyard grass cover.
- Increase the risk of erosion if the soils are sloped.
Undergrazing
Undergrazing causes other problems:
- Loss of quality and decrease in nutritional value (energy and nitrogen) of the cover plants.
- Refusal by animals who do not like to consume mature plants.
Sheep management
Animal needs during grazing
The needs for each category of animals are calculated based on LU (Livestock Units) referencing the average standard of 15 kg of DM per day, i.e.:
- 2.25 kg of DM per day for a ewe (1 ewe = 0.15 LU)
- 2.25 kg of DM per day for a ewe lamb (1 ewe lamb = 0.15 LU)
- 0.75 kg of DM for a grass-fed lamb (1 lamb = 0.05 LU)
- 2.25 kg of DM per day for a goat (1 goat = 0.15 LU)
Flock composition
The composition of flocks grazing the vineyard varies from one situation to another:
- Most animals used are lactating ewes and their lambs, as lambing mostly occurs in autumn. Some farmers prefer ewes over ewe lambs because the latter are more restless and can damage young vine plants.
- To start grazing vineyards, it seems preferable to have at least a group of 20 ewes grazing the vineyards, to "maintain herd behavior."
- Regarding breeds used, some prefer to use "calm" ewes (Merinos, Mourerous) accustomed to vineyards. Ewes that have never grazed in vineyards may wander a bit in the plot at first but this only lasts a short time.
Ouessant sheep - Some farms use small size sheep, of the Ouessant breed, to avoid damaging the vine shoots and excessively attacking the leaves.
Herd management
The herd can be corralled and/or guarded.
Guarding is preferred when:
- Plots are small.
- The herd returns every evening to the sheepfold.
- Grass is abundant (in this case, it is easier to guard the herd because the ewes move little).
Some shepherds use netting or benefit from fixed fences to assist guarding, allowing better management of available resources and saving time.
It is easier to manage animals with movable fences, letting them graze the grass at will. It is advisable to make fairly large paddocks, with 10 to 15 nets, depending on the terrain configuration and available plots, and to leave "turning areas" in the paddock so that the ewes can distribute well between rows.
Using large paddocks has several advantages:
- Greater flexibility in grazing management.
- Easier herd monitoring.
- Reduced risk of equipment theft. To limit theft risks, it is better to place fence posts and batteries inside the paddocks with a padlock and attach them to vine stakes or posts. Regarding the number of electric posts, two posts are recommended for large paddocks. Power supply is by batteries or mains if a network is available near the plots.
However, care must be taken not to make paddocks too large compared to the herd size, as this presents various risks:
- Uneven use of the paddock by the ewes.
- Presence of ungrazed areas.
- Decrease in the amount consumed by the animals.
Thus, a paddock is considered "too large" when the grazing duration exceeds 2 weeks in autumn and 3 weeks in winter.
To ensure homogeneous grazing impact, it is advised to avoid creating paddocks with heterogeneous vegetation or topography. Also, cuts perpendicular to the slope are preferred to prevent ewes from always staying at the top of the paddocks and neglecting the lower parts. Water points can also be placed to direct grazing towards less frequented areas by the ewes.
Grazing pressure can be a lever to ensure good renewal of grass cover. If there is undergrazing (below 10 ewes/ha), animals may select what they eat, create paths, overgraze some areas and underuse others.
Herd monitoring
The risk of predation by stray dogs or wolves as well as theft of animals or equipment requires farmers to increasingly use livestock guardian dogs. Using these dogs requires setting up information signs about the presence of guardian dogs and the behavior to adopt towards these dogs, within the framework of multi-use of the environment.
These dogs can cause some difficulties for vineyard grazing:
- Difficulty of access to plots for people working in the vineyards.
- Increased sudden herd movements that can damage irrigation installations.
Recommendations for grazing grass-covered vineyards
Grazing period
From the end of hardening (end of October) until budburst of the vines (end of February or even March depending on the grape varieties and regions).
For good vineyard grass cover and good flock nutrition, grazing periods must also be reasoned according to the grass growth. To provide ewes with sufficiently abundant rich grass, it is preferable to start grazing when the grass is at hock height, between 7 cm minimum and 20 cm maximum; going beyond risks refusals.
Vineyard layout
- Plan for blocks of at least 15 to 20 ha grouped together, with pastures or fallow areas as fallback zones in case of heavy rainfall. This avoids trampling of grass and waste. In case of rain, it is also necessary to keep "clean" areas (parts where animals have not grazed) to avoid damaging the grass cover and prevent animals from attacking vine wood.
- Consider the organization and schedule of vineyard work: pre-pruning, pruning.
- Agree with the winemaker to define machinery access to plots before setting up electric nets…
- To avoid damaging irrigation equipment, the hose should be hung on the wire at least 60 cm high and sprinklers at a minimum height of 40 cm. Animals should not be left too long to avoid damaging the irrigation equipment, by limiting animal movements in the plot.
Impacts of viticultural practices on grazing
Vine pruning and shoots on the ground
Usually done just after leaf fall but can extend much longer, vine pruning leaves shoots between vine rows. These are later shredded, collected, or left in place. Entry of the herd between pruning and shredding is generally to be avoided for several reasons:
- Scattering of shoots by sheep reducing shredding efficiency.
- Setting up nets by shepherds made difficult by shoots on the ground.
Thus, pre-pruning, which limits the presence of large shoots on the ground, is preferred by farmers as it leaves only small shoots on the ground, which are not problematic for grazing, and in some cases allows simultaneous vine pruning and guarding.
Fertilizers and phytosanitary products
Herbicides can limit grazing possibilities for several reasons:
- Risks to ewe health. Some recommend bringing the herd into the vineyard after a rainfall episode so that leaves are cleared of most phytosanitary residues.
- Decrease in diversity of food resources for ewes. Herbicide use can select, by flora inversion, species unpalatable to ewes (Cape ragwort, Tagetes,...). Some recommend waiting 2 years to allow vegetation to regenerate.
- Accumulation of copper in ewe livers which can sometimes cause death. Preventively, some farmers provide ewes with liver-detoxifying plant-based products.
Fertilization can also hinder ewe grazing, but to a lesser extent:
- In the case of organic fertilization, manure or pellets are not always incorporated, which can disturb ewes if spread in autumn.
Soil work
Soil work restricts grazing of vineyard areas:
- Delays herd arrival, if done just after harvest.
- Destroys grazable surfaces, if done when ewes are present.
- Decreases vegetation cover density, so the farmer must have large areas.
- Leads to selection of ruderal species not consumed by the herd, sometimes problematic for wool valorization (vetch notably). Farmers and winemakers can organize so that plowing is done after the herd has passed.
Sowing a cover crop
Sowing a cover crop between vine rows is practiced by some winemakers to provide ewes with more resources and support fertilization. Indeed, by providing ewes with a denser cover, the winemaker extends grazing time and thus increases the amount of manure deposited by animals.
Trellising, irrigation and sheep movement
Trellising and irrigation systems can impact grazing management. When vines are trellised and wires are too low, ewes cannot move freely between rows, complicating herd management, especially if rows are very long. The optimal height for most ewes is 60 cm.
Regarding irrigated vineyards, to limit equipment damage, it is also preferable to have the hose hung on the wire at least 60 cm above ground, and sprinklers at 40 cm.
Summary
Benefits
- Grazing contributions on vineyards for the farmer and flock
- Effects on soil fertility
- Maintaining a short soil cover in vineyards and controlling grass cover allowing reduction of weed control by mechanical or chemical means.
- Reducing risk of water competition
- Reducing risk of disease spread, when ewes consume leaves;
- Valorization of dry areas
- Fire prevention
- Positive social image with consumers
- For the farmer, vineyard grazing can represent up to a quarter of the annual ration and diversifies fodders. This allows a reduction in direct feeding costs. For one month of grazing, the farmer estimates a saving of 22,500 kg of hay, thus between 2,250 and 2,700 euros saved.
- For the winemaker, vineyard grazing saves work time and fuel (1 to 2 passes less), significant savings. For conventional growers, it reduces phytosanitary product purchase costs.
Points of caution
Several points of caution in herd management should be noted:
- Stay calm with the herd to avoid damage to vines, trellising or irrigation.
- Regarding young plants, they can only be grazed if ewes have already eaten well.
- When interplanting is practiced, damage can be observed on young plants if "pits" are present.
- Monitor trampling of vineyards. In case of rain, grazing should be avoided due to risks of damage to vegetation cover and soil compaction, as most farmers interviewed pointed out.
- For the farmer, increased labor due to the need for guarding, almost mandatory.
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