In the wine industry, we often say that to make great wine you need great grapes. The vineyard is where everything begins, and there are many important steps that the vineyard manager and viticulturist need to perform in order to produce high quality grapes. This article will summarize what these main practices are, and why we do them.
Grapevines, like many other plants, monitor the seasons and adapt their growth and “behaviour” depending on environmental indicators such as light and temperature. This can be called their endogenous clock. This clock monitors the different stages of development that the grapevine goes through, called phenological stages. Grapevines are perennial plants, and therefore they go through the same cycle of stages each year. The main different stages that a grapevine goes through annually are dormancy, budbreak, flower-ripening, fruit set, veraison, harvest, leaf senescence, and abscission (Keller, 2015). At each of these stages, the vine growers have various tasks to complete in the vineyard to complement and enhance the growth of the vines and the production of fruit.
One of the first tasks that needs to be performed in the calendar year is pruning the grapevines. This typically takes place somewhere between December and March (in the Northern Hemisphere) but it can vary significantly depending on the exact location of the vineyard, the climate, the age of the vines, and the viticulturist and winemaker’s goals. Pruning (or winter pruning) is the act of cutting away some of the annual vegetative growth of the grapevine in order to control the amount of buds and their spacing for the new season. One year old and two year old wood can be cut away, but sometimes even older wood is removed. This task needs to be performed each year during the dormant stage of the grapevine. There are many different ways that grapevines can be pruned, and it depends significantly on the location, the rules of a particular appellation, the grape variety, how vigorous the vine is, and the end goals of the wine style. The two most common types of pruning are called spur pruning and cane pruning. Spur pruning retains several different spurs with about two buds per spur evenly spaced along the permanent cordon. Cane pruning, on the other hand, takes one or two long canes from the previous year with buds spaced evenly along it. These canes are typically tied along a training wire. The type of pruning often fits very closely with the training system that is used. A training system is a set of posts and wires that helps to position the grapevine in a certain way. This can help to enable mechanization in the vineyard, and it also allows for proper canopy management. This, in turn helps, adequately ripen the fruit and reduce the risk of fungal diseases.
Soil and Vineyard Floor Management:
Another important task that needs to be performed in a vineyard is preparing the soil and managing the vineyard floor. This can take many different forms, including fertilization, cover crop management, mowing, herbicide, and tilling the soil with various machines or animals.
First we will discuss fertilization. There are several different types of fertilizer that can be added to the soil, but fertilization does not necessarily need to be done every year. Grapevines, like most plants, require several different macronutrients (needed in larger quantities) and several micronutrients (needed in small or even just trace amounts). One of the most important macronutrients used by grapevines is nitrogen, and other macronutrients include phosphorus, potassium, calcium, magnesium, and sulfur (Keller, 2015). The best way to assess the nutritional needs of a vineyard is to do a soil analysis. This is done by taking samples of the soil from different depths and different locations, and sending it to a laboratory for testing. Later in the growing season you can also do leaf and petiole analysis to see how the plant is using different nutrients. From this, the viticulturist can make informed decisions about how much and what kind of fertilizer is needed, and if it should be added in one or more doses. Fertilization can be applied using organic fertilizers such as animal manure, compost, synthetic fertilizers, or it can be applied alongside irrigation (which is known as fertigation). Adding compost and manure to the soil can also help to increase the organic matter, which can improve soil quality. The timing of the application of the different nutrients depends on the winegrowing region, the climate, and the nutritional needs, however there are some guidelines that the viticulturist should follow. Many fertilizers are applied to the soil in the fall post-harvest, especially those that primarily consist of macronutrients (mainly nitrogen, phosphorus, and potassium) and those that will be applied in large quantities. At this time the vines have been depleted of most of their energy, but they have not quite entered their dormant (winter) stage yet. Therefore they are still able to take up different nutrients. The soil is not yet frozen at this time, and many parts of Europe experience rain which can help dissolve the nutrients into the soil so that the grapevines can utilize them. However, too much rain can also be a problem, as the nutrients can be washed and leached away from the soil. Therefore, as always, the vineyard manager needs to take into account their particular climate and weather. Manure is also often added in the fall or winter. Foliar applications (application of nutrients sprayed on the leaves of the grapevine) are typically used to apply micronutrients. This is the main form of fertilization during the growing season, and it can be used for small “top-ups” in nutrients based on the results of leaf analysis.
In addition to adding nutrients to the soil and to the grapevines, a vineyard manager may need to work the soil in various ways. This can be done by tilling the top part of the soil. Tillage helps to loosen the soil, aerate it, manage weeds, and it can also help to mix in organic matter or nutrients.
Cover crops can also be an important part of the vineyard floor management. Cover crops are different plants that are grown between the vineyard rows. There can be several benefits of growing cover crops, as well as some disadvantages. Some cover crops are beneficial because they can increase the nitrogen content of the soil (legumes), increase the organic matter of the soil, they can help control vine vigour and create controlled stress in the grapevines by competing for nutrients and water, decrease soil erosion, manage weeds, and more. A disadvantage of cover crops is that they can sometimes compete with the grapevines for water or nutrients too much. Depending on the region and water and nutrient availability, cover crops may or may not be advisable. Therefore it is really important for the viticulturist to understand the type of cover crop, the region of the vineyard, and the water availability of the soil. Sometimes cover crops are just grown during the winter, so that they do not compete with the vines during the growing season, but they still increase the organic matter of the soil. Any grass or cover crops grown between and within the vine rows must also be managed. Periodic mowing (or letting animals graze) can help to keep the area under control and help minimize interference with the grapevines.
In other areas herbicides are used to manage the weeds. This is a cheaper and less labour-intensive option, however there is of course an environmental concern. Depending on the approach taken by the viticulturist, they may or may not use this method.
Another important task that takes up much of the vineyard manager’s yearly schedule has to do with canopy management. This involves all of the different tasks that help to manage the vegetative growth in a year. If using a training system, this can help to manage the new growth and control it in an organized way. It is important to find the proper balance between having enough leaves to allow for adequate photosynthesis so that the grapevine can fully ripen the grapes, and having too many leaves that the canopy is crowded. A crowded canopy can mean that the clusters are shaded and do not properly ripen. It can also mean that there is not enough air flow which can create an environment prone to fungal diseases. This can wreak havoc on the fruit. Therefore the viticulturist will remove some of these leaves or shoots (called leaf pulling and shoot pulling), tuck the vines into the training wires to help organize the growth, and they will also control the vertical and horizontal growth of the vine. This is done by topping (trimming the top of the vines to break the apical dominance) and hedging (trimming the outward growth of the vines). This will also help to optimize the photosynthesis of the vine. The frequency of these tasks will depend a lot on the location and the vigour of the vine, and also if irrigation is available. If the viticulturist is irrigating the vines, they will be more vigorous and may need more frequent canopy management. Therefore creating an irrigation strategy is also crucial to allow for adequate water available to the vines at the right time, while not giving too much. Grapevines should ideally experience a small amount of “stress” so that they can ripen the fruit most optimally. The amount of water given to the vines will also affect the quality of the berries, and a small amount of hydric stress actually creates higher quality berries that have good concentration of flavours without being too watery.
Pest and Disease Management:
Another important role of the vineyard manager is to control pests and diseases in the vineyard. Typically this is done by having several treatments where the viticulturist sprays different natural or synthetic chemicals to the vines. In conventional, organic, and biodynamic grape production, treatments are used. The nature of the spray treatment, and the frequency of sprays, will vary depending on the approach taken. The goal is always to have as few sprays as possible, but spray treatments will vary significantly depending on the growing region, the climate, and the different pests and diseases that are present. Different areas have very different challenges that need to be managed by different strategies.
The last, and possibly most important task that needs to be performed in the vineyard is the harvest. This is an exciting (but busy!) time of year for everyone in the vineyard. Harvest in the Northern Hemisphere is typically between August-October, but it can vary significantly depending on the location, grape variety, and wine style. Deciding on the date of harvest is one of the most important decisions in the entire winemaking process. In the weeks after veraison, and prior to harvest, the viticulturist and winemakers will frequently sample the different vineyard plots, taste the berries, and analyze the juice in the lab for pH and sugar level. Sugar is measured by brix, baume, density, or oechsle, depending on the winegrowing region of the world. This can give an indication of the ripeness of the berries, and also the expected alcohol level that you can achieve in the wine. Harvest can be done by hand, as it is done in many traditional wine growing regions and on smaller estates, or by harvest machine. It is best to harvest the grapes in the early morning so that the temperature is cool, and then to have the grapes brought to the winery immediately so that there is no unwanted oxidation or fermentation of the juice.
Not only are the individual tasks in a vineyard important, but so is the timing. If the vineyard manager misses the timing of a certain task even by a few days, the quality of the grapes can be dramatically affected. Secondly, the vineyard manager needs to be consistent. Since it is a perennial crop, the vines need to be well taken care of year after year, because failure to do so can affect the growth of the years to come.
Keller, M. (2015). The science of grapevines: Anatomy and physiology (2nd ed.). Elsevier Inc. (2010).