Grapes are among the first fruit species to be domesticated and today are the world’s most economically important fresh fruit crop used to make a variety of fresh, dried and processed products such as wine. It has been said that “the secret to great wine starts in the vineyard,” and “you can make poor-quality wine out of high-quality grapes, but you cannot expect to make great wine from poor-quality grapes.” Growing high-quality grapes for premium wine requires the grower to fully understand the principles of viticulture. The new revised edition of the Grape Grower’s Handbook is a complete rewrite and provides the grower with a broad spectrum of expertise and knowledge in growing grapes for wine grape production in commercial vineyards. Some books offer a strong academic perspective with little practical application on growing grapes for wine production, others books offer a broad overview on growing grapes but provide little detail while most books narrowly focus only on more traditional topics of grape growing. Unlike most books on growing grapes for wine production the Grape Grower’s Handbook is meant to be a stand-alone publication that describes all aspects of wine grape production. The book is written in a nontechnical format designed to be practical and wellsuited for field application. Some of the topics discussed but not limited to include grapevine growth, varieties, rootstocks, climate requirements, training and pruning, canopy management, development and nutrition, water and soil management, pests and diseases, pesticide application, frost protection, winter protection of grapevines, cover crops, and pre-harvest operations. The book is thoughtfully organized presenting a seamless flow of topics within chapters making it easy to find specific information that interests the reader. The information in this easy-to-use guide is distilled from a variety of sources and has the added value of numerous citations so interested readers can research topics in greater detail if desired. No one concerned with the growing of grapes for wine production can afford to be without this book.
Grapevines are long-lived deciduous plants that have long been cultivated for the production of wine. The annual growth cycle of the grapevine involves many processes and events in the vineyard each year. From a winemaking perspective, each step in the process plays a vital role in the development of grapes with ideal characteristics for making wine. Annual growth of grapevines is frequently described using the following stages: 1) budburst, 2) flower cluster initiation, 3) flowering, 4) fruit set, 5) berry development, 6) harvest, and 7) dormancy. The passing of each event announces the beginning of a new stage in the vineyard management cycle. The timing and duration of events are subject to variations due to the grape variety, local climate, and seasonal weather, but the sequence of events remains constant. It is recognized that many of these events overlap others for a period of time, requiring the vine to allocate its resources among competing activities. From a husbandry viewpoint, knowledge of a plant’s growth stages is advantageous as cultural and chemical practices can be applied at optimum times in a plant’s annual growth cycle. Additionally, information regarding growth stages can be useful in estimating crop yields.
Wine grape varieties of commercial importance represent only a fraction of thousands of grapevine varieties grown throughout the world. The majority of those cultivated for wine production belong to the European vine species Vitis vinifera, which has been used to produce wine for more than six thousand years. In contrast to European varieties, there are many different species of grapes native to America that are commercially grown. The best known species is Vitis labrusca. There are also French- American varieties that are hybrid crosses between European and native, American varieties. Vinifera varieties are considered by many to be the best for producing world-class wines. Each different grape variety has its own particular character, defined by flavor, color, berry size, phenolics, and the balance of sugars and acids contained in the fruit. Exactly how a grape variety’s characteristics manifest in finished wines is dependent on many factors, the most important of which is the terroir—soil and microclimate within the vineyard—viticultural management practices and the chosen winemaking technique. A named, cultivated grape variety is formally referred to as a “cultivar.” However, the more common designation of “variety” is used in this book because of its greater use in non-technical publications. In Europe, the finest wines are known primarily by their regional names (Chardonnay and Pinot Noir, for instance, are the major grapes of the Burgundy region in France). Elsewhere, however—as in Americas, Australia, South Africa, and New Zealand—most wines are labeled by their varietal names. In addition to choosing the right variety in planting new vineyards the grower can select clones based on flavor profile, berry size, cluster shape, vine yields, vine vigor, bud break, and tolerances to heat, humidity, and drought.
Until the mid-1800s, European vinifera vineyards consisted of own-rooted vines. The inadvertent introduction of phylloxera (Daktulosphaira vitifoliae) with the importation of American grape varieties changed that, and the European wine industry was nearly destroyed. American grape varieties that evolved in the presence of phylloxera are tolerant to their feeding, meaning the vines can survive and be productive in the presence of phylloxera. Vinifera grapevines are susceptible (have no tolerance) to feeding by phylloxera. While many native varieties can be grown successfully on their own roots, V. vinifera and many hybrid varieties need to be grafted. Aside from phylloxera resistance, rootstocks can be used to combat other soil-borne pests, primarily nematodes. They may also be used to overcome vineyard problems such as drought, adaptability to high pH soils, adaptability to saline soils, adaptability to low pH soils, and adaptability to wet or poorly drained soils. Numerous reports have also proved the rootstocks affect vine growth, yield, fruit quality, and wine quality. These effects take place in a more or less indirect manner and are consequences of interactions between environmental factors and the physiology of the scion and the rootstock varieties employed.
Vineyard site selection is probably the most important, fundamental, irreversible decision in the life of a vineyard. It takes several years to develop and establish a vineyard and for the vines to produce a regular crop of grapes with the vineyard remaining productive for many decades. Although the grapevine can grow in many places, its successful cultivation for quality wine production is limited to sites where specific characteristics and conditions occur and the necessary management practices can be achieved. The main factors affecting vines, their development and annual cycle of growth, and the crop produced each year include: physical environment (e.g., landform, altitude, slope, aspect, natural & built features, soils, nutrients, water & drainage); natural phenomena (e.g., climate, heat summations, seasonal variations, longer term cycles and fluctuations, weather & hazards); viticulture and vineyard management (e.g., selection of sites, design and layout of vineyards, varieties and rootstocks, infrastructures & services such as irrigation). All of thee factors contribute to the terroir of a region’s wine. Terroir (pronounced tair-wahr) is a French concept in which a complex interplay of physical factors and cultural influences interact to define the wine styles and quality that come from any vineyard site or region.
Vineyard establishment involves careful planning in site preparation and vineyard design. Wine grapes are a very capital-intensive crop, so a well planned, organized vineyard will prove to be more efficient, requiring less input and offering larger potential returns. Mistakes made in the establishment of a vineyard can be very costly and have long-standing consequences. Some cultural practices can be changed as a wine grape grower accumulates experience, but many pre-planting decisions are permanent, and so should be carefully considered when establishing a vineyard.
Establishing a commercial vineyard with clean planting stock derived from disease-tested stocks is paramount to insure the long-term sustainability and success of the vineyard. The grapevines will most likely be one of the greatest initial capital expenses, and other than proper site selection, may be the most critical pre-harvest decisions to make. Choosing the best planting stock for a particular site is a key factor in the production of premium wines. The use of certified, disease-free grapevines can have an impact on survival, growth rate, susceptibility to pests and diseases and the quality of fruit—all of which affect profitability.
Proper planting and training of young grapevines is essential for the establishment of a productive vineyard. The objective of is to achieve a uniform planting of strong, healthy, well-shaped vines that meets the requirements of the training system. To achieve this, all initial growth is used to develop a strong root system and trunk(s). Attention must be paid to all vineyard practices to ensure adequate growth and development of young grapevines. If badly managed, delays in the development of a uniform vineyard will occur with some probability the vineyard will never reach its full potential.
A trellis is needed to support the foliage and fruit since the grapevine does not have a rigid trunk. Not only does the trellis support the weight if the fruit, but it spreads the grape canopy ensuring sunlight penetrates all parts if the vine in addition to promoting good air circulation which is essential for keeping down the incidence of disease. A trellis system can be as simple as a single wire in a high cordon system to as complex as a number of catch wires at various heights as in the case of a Lyre trellis. The types of trellis systems used worldwide are numerous, and no single system is appropriate for all situations. Deficiencies in design, materials or construction can result in deficiencies in vineyard performance leading to excessively high maintenance costs throughout its life cycle. Trellis construction represents a major investment in both time and money.
Profitable grape production requires that grapevines be managed so that a large crop of high-quality fruit is produced each year. Grapevines must be pruned and trained annually to achieve this goal. The term dormant pruning refers to the annual removal of wood during the vine’s dormant period. Grapevines are pruned primarily to regulate the crop but also to maintain a vine conformation consistent with the desired training system. Pruning is used to selectively remove unsuitable or extraneous canes, retaining a small number of good canes. Canes are carefully selected to serve two functions: 1) produce fruitful shoots in the coming season, and 2) produce healthy shoots from which a good fruiting cane can be selected in the next dormant season. Training positions the fruit-bearing wood and other vine parts on a trellis or other support so as to shape the vine. The basic goal of training is to maximize production, facilitate vine management (i.e., spraying, tillage, pruning, harvesting), improve canopy microclimate and to support the mechanical load of the vine.
Vineyard canopy management is employed to optimize yield, improve fruit quality, reduce the risk of disease, and facilitate other vineyard operations. These objectives are generally achieved by improving the microclimate of the grapevine through the use of shoot positioning, shoot thinning, hedging, leaf removal, and cluster thinning. These management practices can improve light interception, which promotes sugar accumulation and acid composition, improves phenolic compounds (for red grapes), reduces levels of methoxypyrazines, and improves development of aroma and flavor compounds. Since light interception also affects bud development, fruit set, and berry growth, shading can negatively affect crop levels. Open canopies tend to have reduced disease pressure, since improved airflow reduces humidity, which allows better penetration of fungicides and insecticides. Finally, vine vigor can also be controlled indirectly by management techniques—irrigation, fertilization, and floor management.
Grapevine water management is a key issue for vineyards. Poor water management can result in water stress or over vigorous conditions resulting unbalanced vine growth, reduced yields and inferior fruit quality. How much water is required to grow quality wine grapes is dependent upon evaporative demand at the location of the vineyard, stage of vine development, and percent ground cover by the vine’s canopy, and amount of rainfall occurring during the growing season. One of the most effective tools in managing the water needs of a vineyard is irrigation, which is used to supplement natural precipitation so that vines achieve adequate vegetative growth and berry development. The manner in which water is applied to the vineyard encompasses everything from the decision of when to apply the water, how much water to apply, and the best method in which to apply water. Vineyards can be irrigated with overhead sprinklers, drip emitters, micro-sprinklers, or furrow irrigation; each has its particular advantages and disadvantages.
Good irrigation management is required for efficient and profitable use of water for irrigating the vineyard. A major part of any irrigation management program is the decision-making process for determining irrigation dates and/or how much water should be applied to the grapevines for each irrigation. This decision-making process is referred to as irrigation scheduling. To ensure that the vines are neither over, nor under watered requires constant monitoring of a number of factors including weather conditions, the amount of water stored in the soil from winter rains, the stage of development of the vines and the vineyard, the soil type(s), the irrigation system type, and its efficiency. Irrigation scheduling, which determines the time and amount of water to apply is usually based on four methods: 1) monitoring soil moisture levels by hand or with various instruments, 2) measuring plant-water status, 3) evapotranspiration-based, and 4) a water balance method based on the estimated crop water use rate and soil water storage. Many of these techniques are proven and have been in use for years for growing wine grapes. In reality, irrigation scheduling is most often a combination of the three basic techniques. The benefits of irrigation scheduling are widespread including cost efficiencies on electricity, water, labor, soil health, nutrient retention, and minimizing any detrimental environmental side effects such as nutrient leaching. Not adhering to an irrigation schedule may contribute to poor vine balance, excessive or poor vigor, decreased berry set, early berry dehydration, nutritional imbalances, and inconsistent yield and quality of fruit.
Micro-irrigation is the standard water delivery method for vineyards. Micro-irrigation consists of frequent low volume, low pressure application of water on the soil surface by an outlet device called an emitter. Emission devices used consist of emitters that are either in-line (integrated inside the tube) or on-line emitters (external on drip tube), and mico-sprinklers systems (used primarily in vineyards on sandy soils or for growing cover crops). Micro-irrigation is the most efficient way to supply supplemental moisture to grapevines. A well-designed micro-irrigation system loses practically no water to runoff, deep percolation, or evaporation. Micro-irrigation reduces water contact with grapevines leaves, stems, and berries. Thus, conditions may be less favorable for disease development. Irrigation scheduling can be managed precisely to meet grapevine demands, holding the promise of increased yield and fruit quality. Micro-irrigation is also referred to as drip or trickle irrigation.
Deficit irrigation strategies are commonly employed in growing wine grapes to reduce water consumption, control vegetative growth, and improve fruit and wine quality. In general, moderate water deficit affects a host of fruit quality attributes, such as berry size, seed maturity, acidity, pH, tannins, flavonols, and color. Two irrigation techniques that have been shown to be useful for this are Regulated Deficit Irrigation (RDI) and Partial Rootzone Drying (PRD). These two methods of irrigation do, however, differ fundamentally in two key respects. With regulated deficit irrigation water application is manipulated over time whereas, with partial rootzone drying, irrigation is manipulated over space. With regulated deficit irrigation, a water deficit is applied in a vineyard over a critical period (i.e., after fruit set and up to véraison or harvest). By contrast, partial rootzone drying relies on separating alternating dry and moist roots with an irrigation system that can produce the desired pattern of soil wetting. Partial rootzone drying can be targeted to a particular grapevine growth phase but is usually maintained during an entire growing season.
The water quality used for irrigation is essential for successful wine grape growing. Poor water quality can affect grapevine growth, and can even result in the gradual death of the vines. Water quality properties can be divided into three categories: physical, biological and chemical. Critical physical properties include suspended solids and temperature. Suspended solids such as soil particles are potential problems since these particulates can clog irrigation nozzles and cause abrasion of irrigation equipment. Important biological properties include algae, microbes and disease organisms. Chemical properties are typically given the most focus when dealing with irrigation water. From the wine grape grower’s standpoint, the most critical chemical water quality parameters are soluble salts, hardness, sodium and chloride concentration, and pH. In a few cases, elements such as iron, boron and fluoride are also considered critical parameters.
Grapevine nutrition plays a major role in the life of the vineyard; therefore, the nutrients in the soil and vines must be monitored on a continual basis and maintained for optimal efficiency. Since this is a constantly changing situation, it is best to set up a regular program of soil and tissue (e.g., petiole or leaf blade) sampling and analysis to avoid mineral deficiencies and unnecessary application of fertilizers. The interpretation from the analysis of the tissue and soil samples should always be used together with visual observations made in the vineyard. Although the mineral elements are needed in different quantities, each one plays an essential role in completing the vine’s life cycle. Macronutrients such as nitrogen, phosphorous, potassium, and magnesium are used in relatively large quantities by vines. Micronutrients such as boron, iron, manganese, zinc, and molybdenum, although no less essential, are needed in very small quantities. When one or more of these elements is deficient, vines may exhibit reduced growth or yield and greater susceptibility to diseases and winter injury. This may also result in other problems such as fruit with a low or high pH, poor color, low phenolics, stuck fermentations, and undesirable flavors. The availability of essential nutrients is, therefore, critical for optimum vine performance and profitable wine grape production.
Proper nutrition is a key requirement for the reliable production of grapevines. Like other plants, grapevines require nutrients for growth and fruit production. Fertilizers supply nutrients to soils and help to correct nutrient deficiencies. Fertilizer refers to any compound that contains one or more chemical elements, organic or inorganic, natural or synthetic, that is placed on or incorporated into the soil or applied to directly onto the vines to achieve normal growth. There are various types of fertilizers available for use in vineyards, each of which are suited to different situations and serve different purposes. With the increased cost of fertilizers and concerns about the adverse environmental impacts, there is great interest in fine-tuning fertilizer management. The goal is to match application source, rate, timing and method to meet the grapevines needs and achieve optimum levels of fertilizer use efficiency.
Fertigation is the application of dissolved fertilizers through an irrigation system to the vineyard. Most commonly this is done through a drip irrigation system but it can also be done with microsprinklers. Using a fertigation system, a wine grape grower can apply fertilizer anytime, and place it where the grapevine roots are most numerous and active. In addition to greater flexibility in application timing and placement, fertigation increases the rate of nutrient uptake and predictability of vine response to fertilization compared to band and broadcast applications. Effective fertigation requires knowledge of certain grapevine characteristics such as optimum daily nutrient consumption rate and root distribution in the soil. Nutrient characteristics such as solubility and mobility are important and irrigation water quality factors such as pH, mineral content, salinity, and nutrient solubility must be considered. The macronutrients nitrogen, potassium, phosphorus, and magnesium are the most common nutrients applied by fertigation, but micronutrients such as boron, zinc, iron, calcium manganese, and copper can also be applied through the irrigation system. In addition, to fertilizers other chemicals can be injected through the irrigation system, including chlorine, acid, herbicides, nematicides, and fungicides.
The grapevine is a long-lived perennial that has a 40- to 50-year life of a commercial planting. This means that the relationship between soil and vine must be as harmonious as possible. Soil provides not only mechanical support for the vines, but more importantly, the soil supplies water and nutrients that influence the vigor of the vine, the balance between vegetative growth and fruit, the yield of grape berries, and berry quality. A number of pests and diseases of grapevines, such as nematodes, phylloxera, and the spores of the downy mildew fungus, live in the soil and can have a profound effect on the health and longevity of the vines. Maintaining the soil in good condition physically (soil structure), chemically (adequate nutrients and no toxicities), and biologically (organic matter turnover and biodiversity) is important for sustained yield and vine longevity. They all have a major influence on the growth of grapevines and ultimately on the long term sustainability and success of a vineyard.
Disease management is an important and integral part of wine grape production. Grapevine diseases are caused by microscopic organisms referred to as plant pathogens. There are several categories of these organisms that may be damaging to plants such as fungi, bacteria, and viruses. Vineyard disease management practices rely on anticipating occurrence of disease and attacking vulnerable points in the disease cycle (i.e., weak links in the infection chain). Therefore, correct diagnosis of a disease is necessary to identify the pathogen, which is the real target of any disease management program. A thorough understanding of the disease cycle, including climatic and other environmental factors that influence the cycle, and cultural requirements of the host plant, are essential to effective management of any disease.
Pest management is an important and integral part of wine grape production. Pests cause extensive damage and are responsible for two major kinds of damage to grapevines. First is direct injury to the grapevine by pests feeding on leaves, shoots, roots, and grapes. The second type is indirect damage in which the pest itself does little or not harm but transmits a bacterial, viral, or fungal infection to the vines. To manage these pests in the vineyard, it requires implementing an integrated pest management program, which consists of the following: 1) monitoring the populations of the major pest species in the vineyard; 2) using action thresholds based on pest populations to determine when a spray should be used to control a pest; and 3) when possible, using an effective and safer alternative to reduce pest populations.
Nematodes are microscopic, unsegmented roundworms present in most soils that feed on vine roots. Nematodes are a major economic problem in every major grape production region in the world. Plant-parasitic nematodes can cause direct and indirect damage to a vine. Nematode feeding can cause direct damage by stopping root elongation, killing plant tissue, changing root growth patterns, and by removing plant nutrients. Their feeding patterns fall into two categories: some feed externally on roots (ectoparasitic nematodes), while some penetrate into roots and feed internally (endoparasitic nematodes). Indirectly, plant-parasitic nematodes can damage plants by vectoring viruses or by increasing the severity of other plant diseases, such as Pythium, Fusarium, Rhizoctonia, and Phytophthora. Nematodes like other pests take advantage of vines that are under stress as a result of management practices and/or other biological pressure.
Weeds can present problems in vineyards, as in many cropping systems. Weeds compete with grapevines for water, light, and nutrients; however, the effects of this competition vary throughout the life of the vine. Weeds may also serve as alternate hosts for disease pathogens, nematodes, and insects; they may also serve as a habitat for vertebrate pests. They may interfere with harvest, spray equipment, and other cultural operations. Weed competition is most critical during the early stages of vine growth, usually the first three years after planting. Weed competition can decrease survival, severely retard vine growth, and prolong the time before a vineyard comes into production. In established vineyards, the critical period of weed competition is from bloom until véraison, when days are long, grapevine leaf area is maximized, and when soil moisture may be limiting. During winter months, presence of weeds as a ground cover is not considered to be a problem and may not adversely affect the vines. In fact, weeds may help conserve soil and improve tilth and access to vineyards during winter months.
There are many pesticides available for use in vineyards, all of which control specific pest and disease problems in growing grapevines. Pesticides include any substances used either to directly control pest populations or to prevent or reduce damage in the vineyard. Although many pesticides are designed to kill pests, some may only inhibit their growth, or simply attract or repel them. The most commonly applied pesticides are herbicides (to kill weeds), fungicides (to control fungi), and insecticides (to kill insects).
When developing an integrated pest management strategy, it is important to know the target pests, their economic threshold levels, and multiple control strategies that can minimize pesticide inputs in the vineyard. However, in many cases, pesticides need to be applied as a last resort to reduce pest infestations and optimize grapevine production. The objective in applying pesticides in vineyards is to deliver an effective, uniform dose to a target area in a safe and timely manner. Inaccurate pesticide application is expensive and can result in wasted pesticide, marginal pest control, compromised worker safety, and possibly excessive pesticide carryover contributing to water contamination and/or vine damage. Many types of application equipment are available to apply pesticides. Some types can be used in a wide range of situations whereas others are highly specialized and are only used for a few specific pesticides.
Vineyards provide food and shelter for vertebrate pests that can cause significant through loss of fruit, chewing of roots, and girdling or trunks and shoots. Grapevine injury by rodents, rabbits, or deer is often more serious, killing the vine outright or causing permanent damage that lowers yields for years following the initial feeding. Some pests will chew or destroy flexible irrigation lines and emitters. Other pests will dig holes through the soil surface, thereby channeling surface irrigation water to undesired areas. Food safety also becomes an issue if pest residues come into contact with the fruit. The extent of the damage varies by region and vineyard due to differences in climate, terrain, and wildlife. The major vertebrate pests are deer, pocket gophers, ground squirrel, rabbits, and birds. Ideally some combination of habitat modification, exclusion, repellents, and lethal methods (e.g., trapping, toxic baiting, burrow fumigation, etc.) can be used to effectively control these pests in the vineyard, as well as maintain healthy wildlife populations and ecosystems.
The best protection for avoiding a spring frost is locating the vineyard on a proper site. However, most sites are not perfect, and may benefit from additional frost protection. In the spring, frost has the potential to kill young vines, reduce or destroy the crop for that season, and reduce the potential yield for the following season. In general, younger tissues tend to freeze at a higher temperature because they have a greater, water content, hence shoot tips, emerging leaves and developing inflorescences tend to be most sensitive to a frost. Vines that have not broken bud are less prone to damage. In the fall, frost before harvest will lead to premature leaf fall. This effectively prevents any further photosynthate accumulation by the vine, the transfer of nutrients from the leaves into the vine, and the accumulation of sugars in the berries. The focus of this chapter is on practical considerations related to what has been traditionally called spring frost protection.
Cold damage to grapevines is a worldwide concern but is especially prominent in regions that experience low-winter temperatures. Cold-winter temperatures can damage the buds, canes, cordons, trunks, or roots, and even kill the vine. The plant tissues are injured more when there is an exceedingly fast drop in temperature at night during the winter. Winter injury is also the major cause of crown gall disease development in vines. The economics of these losses to winter injury can be devastating to a vineyard business affecting a vineyard’s profitability for many years. While growers can’t control the weather, they do have some control over their grapevines’ ability to survive through the winter with minimal damage.
A cover crop is a noneconomic crop that is grown in the vineyard to prevent soil erosion, suppress weeds, maintain soil structure, provide easier access during wet weather, and contribute to soil fertility through organic matter. Cover crops may also contribute to insect and mite pest control, depending on the pests present and the conditions. An ideal vineyard floor should be easy to maintain, aid the growth of the grapevines and fruit, maintain the soil structure of the vineyard, reduce erosion potential, and not compete with the vines for water or nutrients, nor harbor insects or other pests. In practice, no single vineyard-floor management system accomplishes all of these goals, but rather a balance of the above factors should be achieved while also considering the soil type, slope, age of vines, irrigation, and harvesting methods. Cover crops are increasingly being recognized as an important component of “sustainable” production in most wine producing regions of the world.
Estimating wine grape yields is a process of projecting as accurately as possible the quantity of crop that will be harvested for a vineyard. In normal situation, the grapevine yield can be variable from year to year (10 to 20%), thus yield estimation is essential to help make decisions, both for the grower and the vintner. Grape growers are concerned about the yield, to ensure that fruit composition target values are met, and to maintain the vine size for a future crop. Early forecasts of grape yield can significantly enhance the accuracy of scheduling labor, delivery, purchases of related materials and so on. Wineries need to know how many grapes they will be expected to process in a vintage. This affects their logistics, from the tank and barrel space to scheduling of grapes for processing. Crop yield is a function of three factors—the number of bearing vines, the number of clusters per vine, and the cluster weight.
There are many aspects in evaluating wine grape maturity that determine the best time to harvest wine grapes. Some of these are quantitative and can be determined to a high degree of numerical accuracy, and others are qualitative and are more subjective. Some of the quantitative measures include soluble solids content, titratable acidity, and pH for the intended type and style of wine. Of equal importance are the grower’s observations of the qualitative indicators—integrity of fruit, color intensity of skins, seed coat color, the degree of tannin “ripeness” when the skins are chewed, degree of lignifications of the cluster peduncle development, and observations of the physical condition of the vines. Practical and economic considerations play a role too and may include availability of labor and weather conditions.
The harvesting of wine grapes is one of the most crucial steps in the process of winemaking. Manual harvesting and mechanical harvesting are the two routes that a wine grape grower can take to get the grapes off the vine and ready for the crush. Hand-harvesting affords more precise selection and tends to do a better job of protecting the grape’s juice content from oxidation due to damaged skins. Mechanical harvesters allow for a more efficient, often cost-effective, process and are well-suited for large vineyards that lay on a flat patch of earth. In general, sparkling wine grapes are harvested first (Chardonnay and Pinot Noir) to ensure lower sugar levels followed by most of the white wine grapes. Red wine grapes are typically next in line to harvest, as they take a bit longer to reach full maturation. Finally, the dessert wines make their way to crush after undergoing some dehydration on the vine to produce a raisin-like grape with highly concentrated sugars.
Precision viticulture is generally considered to be the application of one or more of the geospatial technologies and other related devices, tools and techniques that use spatial location for the purposes of collecting, processing, analyzing, and visualizing environmental data collected in a vineyard. Precision viticulture is considered to be an approach to wine production based on recognition of the fact that the productivity of vineyards and individual blocks within a vineyard can be inherently variable over space and time because of differences in topography, soils, soil moisture, slope and aspect, plant health and vigor, microclimate and management practices. Variability in the environment ultimately leads to variability in grape yield (quantity) and quality and ultimately wine production. There are four major components of technology used for precision viticulture management practices. They are global positioning systems (GPS), remote sensing, geographical information systems (GIS), and variable rate application (VRA). The global positioning system (GPS) is a satellite constellation used to geo-reference spatially referenced vineyard data (e.g., soil samples, yields, etc.), or some other grapevine management practice within the vineyard block. Geographic information system (GIS) enables the convenient capture, storage, manipulation, and management of spatially aligned, geographic data layers. Remote sensing refers to capture of digital imagery of the Earth’s surface by aircraft and satellite. Variable-rate application (VRA) describes any technology, which enables growers to vary the rate of inputs.