How to use Cover Crops in Vineyards and their Advantages
Cover crops in vineyards
Erosion, soil degradation due to extensive farming and tillage, biodiversity loss, and loss of water and moisture from topsoil are just some of the problems farmers face nowadays in every crop system, and vineyards are no exception.
One of the possible answers to those problems could be cover crops. Although using cover crops dates as far back in history as winegrowing itself, it’s still an object of discussion whether cover crops are better than conventional soil management methods, but there are some proven benefits of this system. Conventional methods like tillage, which require machines and tractors, put pressure on the soil to a depth of about 15 cm, making the topsoil less permeable. Also, vineyards placed on inclined terrain are in great danger of losing soil to erosion.
Growing cover crops in vineyards is nothing new, but it is definitely becoming more common, especially in organic vineyards. Planted between the vine rows and sometimes under the vines, they should be introduced into the vineyard five or six years after planting the vineyard.
The cultures we choose can vary from year to year. This depends on our goals. Crops should be able to form a firm turf and have root systems that are capable of binding the soil.
Cover crops have multiple roles and benefits. Some of them are the:
- positive impact on biodiversity in the soil
- improvement of the organic content in the soil that leads to a better aggregate structure of the soil
- reduction of the negative impact of compacted soil due to agricultural machinery
- erosion control: by covering the soil surface, they are effective at reducing raindrop impact and slowing surface water movement, which can be particularly problematic on sloped terrain
- enhancement of water absorption and air capacity
- preservation of the moisture by leaving a ”carpet” that is left on the surface after mulching
- help with low-temperature resistance
- facilitate the movement of machines through the rows (the soil is less muddy)
As a result, this strategy of wine growing can improve soil quality and reduce soil degradation.
Like everything else in farming, cover crops can also have some negative effects. For example, they can provide conditions for rodents and other pests, become hosts for specific diseases, or simply present competition for nutrients and water.
To prevent crops from competing with the vines for water and nutrients, we must choose them carefully and apply them rationally. To respond to pests and pathogens, crop rotation is advised to prevent and control diseases in the vineyard.
Types of cover crops suitable for vineyards
Cover crops can be divided into three major groups, each with specific properties that make them desirable in the vineyard ecosystem.
Grasses (barley, wheat, oat, rye, etc.):
- useful for erosion control
- fast growing
- easily managed residue
- accumulate soil nitrogen in symbiosis with Azospirillum but not able to fix nitrogen from the atmosphere
Legumes (fava beans, cowpeas, clovers, alfalfa, etc.):
- nitrogen-fixing plants
- more extensive root systems help maintain the soil structure
Broadleaf non-legumes (radishes, mustard, etc.):
- absorb soil nitrogen
- holds the soil in place (protects from soil erosion)
- can be used for green manure
Depending on the local environmental conditions (soil pH, nitrogen and water availability, salinity, shade, temperatures, etc) the farmer may choose to apply some of the above mentioned species in mixes (e.g., legumes and grasses). The ratio of each part may vary.
When using cover crops in our vineyards, we have a few options to choose from, but it mostly comes down to the till or no-till approach.
In the till approach annually, seeded cover crops (barley, wheat, winter peas) are used; they grow from autumn until spring and then are tilled. This method requires tilling, which can disrupt the topsoil and leave it exposed to sunlight during hot periods.
If winegrowers do not want to till their soil, there are a few options, where the cover crop is mowed or mulched and left to lie on the surface. These options are:
- cultivars that will reseed themselves (some clovers and grasses)
- annually seeded plants (barley, wheat, broad beans)
- perennial plants or native grasses (alfalfa, red clover)
Farmers often opt for a mixed approach where cover crops are grown every other row, so we have one row with the tillage system and the other not tilled. Rows can then be switched every year or every few years.
The right choice of species grown (or a mixture of seeds) for this use is vineyard site-specific. It depends on many factors such as soil type, incline, microclimatic factors, and finally, the winemaker’s goals.
One study done in warm, humid, and moderate Mediterranean conditions showed that a well-developed cover crop containing 50% of clovers could leave to the ground up to 30 kg/ha of fixed nitrogen. Naturally, choosing this seed mixture on nitrogen-rich soil would not be the best idea.
The objective of the study conducted on the Tempranillo grape variety in La Rioja (Spain) was to determine the influence of barley and clover cover crops on grapevine nutritional status and the availability of N, P, K, and Mg. Cover crops did not affect the uptake of P, K, and Mg. Nitrogen availability decreased after a year of using barley as a cover crop, while clover led to increased nitrogen availability after two years.
Another study in La Rioja showed an increase in organic carbon, water-soluble carbon, and potentially mineralizable nitrogen five years after cover crops were introduced.
Fescue (Festuca arundinacea) cover crop was the subject of a study in southern Italy that compared the effects of cover crops and conventional tillage during three growing seasons. The results showed that cover crops increased soil organic carbon, total nitrogen, and microbial biomass while having little to no effect on grape quality and yield.
It is important to prepare the soil before sowing the selected plants. This preparation should be done in moderately humid conditions. It is recommended that the surface be well flattened and slightly pressed so the seeds can reach a depth of 0.5 cm – 2.5 cm.
Sowing can be done in late summer, fall, or early spring. Fertilizing the cover crop is unnecessary since the vineyard should be fertilized beforehand. When using herbicides on unwanted plants (for example, under the vines), farmers need to be mindful of a possible drift toward the crops. Mowing should be done before the crop grows too much and develops a big mass since, after mowing, the weight of the mass can negatively impact the remaining crop.
Crops can be mowed or tilled. Tilling is done in spring when there is still enough moisture in the soil to make the process easier. Before tilling, growers usually mow the crop to help decompose the plant residues. If just mowing is chosen for maintaining crops, it can be done in spring or late spring/summer. With spring mowing, the aim is to reduce shading from weed species, and in late spring, cover crops are stopped from growing too tall. In both cases, the mowed residue can reduce the loss of humidity from the soil during dry summer months.
- Mirosevic, N., Karoglan-Kontic, J. (2008.). Vinogradarstvo
- Eva P.Pérez-Álvarez, Enrique García-Escudero, Fernando Peregrina (2015). Soil Nutrient Availability under Cover Crops: Effects on Vines, Must, and Wine in a Tempranillo Vineyard. American Journal of Enology and Viticulture
- Eva P.Pérez-Álvarez, Mikel Colina, Enrique García-Escudero (2012.). Cover crops and tillage influence soil organic matter and nitrogen availability in a semi-arid vineyard. Agronomy and soil science
- Concetta Eliana Gattullo, Giuseppe Natale Mezzapesa, Anna Maria Stellacci, Giuseppe Ferrara, Giuliana Occhiogrosso, Giuseppe Petrelli , Mirko Castellini, Matteo Spagnuolo (2020.). Cover Crop for a Sustainable Viticulture: Effects on Soil Properties and Table Grape Production. Agronomy