Introduction
One of the key principles of regenerative viticulture is to avoid bare soil – keeping the ground covered (see cover crops) also reduces soil temperature during hot periods. Living ground cover also provides habitat and biodiversity within a vineyard.
Furthermore, photosynthesis captures carbon dioxide from the atmosphere. A higher percentage of the ground covered for a higher proportion of the year, therefore, increases overall photosynthetic activity and helps build carbon stored in the soil.
A living soil is best able to furnish the vine with the nutrients it needs and to build resilience to disease.
Mulches or physical barriers can also be used for ground cover, as a form of weed control and to regulate temperatures and evaporation.
Use an m2 quadrant to estimate the % of ground cover in several sections of your interrow and undervine.
In detail
Keeping living roots in the soil is a core tenet of regenerative agriculture. Plants photosynthesise, absorbing CO2 from the atmosphere. Increasing the percentage of the ground that is living soil, supported by living ground cover in a vineyard, has been shown to:
- Increase soil organic carbon, through increasing the amount of photosynthetic activity and pulling carbon dioxide from the atmosphere and down into the soils, i.e. sequestration.
- Improve water infiltration, soil aggregate stability and therefore water holding capacity
- Decrease soil erosion, nutrient leaching and run off
- Increase biodiversity above ground through attracting beneficial insects that are predatory or parasitic of problematic insects
- Increase biodiversity below ground through ‘feeding’ the beneficial microbes in the soil, improving mycorrhizal relationships between vine and soil, increasing nutrient uptake
- Preserve aerobic conditions in the soil, which discourages pathogenic microbes which are generally anaerobic
- Make the vineyard accessible at wetter times of year
- Reduce soil temperatures during heatwaves
- Reduce soil compaction
- Provide opportunity for beneficial plant species regeneration
- Provide a more attractive beneficial landscape
Competition for nutrients between vines and other plant species in vineyards has also been cited as a concern in less vigorous blocks and in newly planted vineyards. In such cases advice from experts/viticulturists should be sought as to the timing, species and management of alleyway cover crops. The careful choice of cover crops is essential in managing this relationship. For example, nitrogen fixing leguminous cover crops, e.g. clover, can increase availability whereas some grasses have high nitrogen demands.
There is a wide choice of cover crops:
- Spontaneous sward, allowed to regenerate naturally with native species
- Perennials, including grasses which mat together as a turf but have high nitrogen demands
- Annuals which are seeding every year
- Self-seeding winter annuals in more arid climates
Seed mixes are available but don’t always result in a wide variety of flowering plants due to them out competing each other. Native species can provide better habitat for beneficial insects. What is critical is that research and advice is sought to ensure appropriate species are introduced to maximise their benefits and reduce competition.
How they are introduced is important too. The spontaneous sward is allowed to regenerate naturally. However, cover crop seeds can be sown either into pre-prepared cultivated tilth of, preferably, by direct drilling into existing sward. There are increasing vineyard tractor attachment options for direct drilling.
Management techniques vary with climatic conditions, vineyard vigour and machinery availability:
- Cover crops are now commonplace in the rows of vineyards in many (but not all) wine producing regions of the world, but the adoption of under-vine planting or sward maintenance is less common. In more vigorous regions, under-vine low growing cover crops can provide necessary competition but need to be mowed or strimmed regularly to reduce humidity and competitive pressure. Animals such as sheep can be incorporated into the vineyard to control growth but not usually during the vine growing season
- In the inter-row, cover crops are often mowed high, infrequently and in alternate rows, to maintain flowers and habitat for beneficial insects
- In arid climates, winter cover crops dry out in late spring and can be crimped and rolled to provide a mulch, reducing soil temperatures and reducing evaporation
Further information on cover crops can be found in the Cover Crops section.