Irrigation in viticulture

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A vineyard with a drip irrigation system running along the bottom of the vines

Irrigation in viticulture is the process of applying extra water in the cultivation of

growing season, to avoid stress.[1]
A vine that does not receive the necessary amount of water will have its growth altered in a number of ways; some effects of water stress (particularly, smaller berry size and somewhat higher sugar content) are considered desirable by wine grape growers.

In many

Institut National des Appellations d'Origine (INAO), has also been reviewing the issue.[3]

In very dry climates that receive little rainfall, irrigation is considered essential to any

foliage. If the vine receives too much water stress, then photosynthesis and other important processes such as nutrient storage could be impacted with the vine essentially shutting down. The availability of irrigation means that if drought conditions emerge, sufficient water can be provided for the plant so that the balance between water stress and development is kept to optimal levels.[2]

History

Advances in irrigation have allowed viticulture to flourish in very dry climates, such as parts of Australia, that might not otherwise be able to sustain grapevines.

The practice of irrigation has a long

agricultural crops since around 5000 BC.[4] It is possible that the knowledge of irrigation helped viticulture spread from these areas to other regions, due to the potential for the grapevine to grow in soils too infertile to support other food crops. A somewhat robust plant, the grapevine's largest need is for sufficient sunshine, and it is able to flourish with minimum needs of water and nutrients. In areas where its water needs are unfulfilled, the availability of irrigation meant that viticulture could still be supported.[2]

In the 20th century, the expanding wine industries of California, Australia and Israel were greatly enhanced by advances in irrigation. With the development of more cost efficient and less labor-intensive ways of watering the vines, vast tracts of very sunny but dry lands were able to be converted into wine-growing regions. The ability to control the precise amount of water each vine received, allowed producers in these New World wine regions to develop styles of wines that could be fairly consistent each year regardless of normal

phenolic compounds that contribute to a wine's quality. This research lead to the development of ways to measure the amount of water retention in the soil, so that individual irrigation regimes could be plotted for each vineyard that maximized the benefits of water management.[2]

Role of water in viticulture

Water is vital to many of the physiological processes of the grape vine, including photosynthesis.

The presence of water is essential for the survival of all plant life. In a grapevine, water acts as a universal solvent for many of the

nutrients and minerals needed to carry out important physiological functions, and the vine receives these by absorbing the nutrient-containing water from the soil. In the absence of sufficient water in the soil, the root system of the vine may have difficulties absorbing these nutrients. Within the structure of the plant itself, water acts as a transport within the xylem to bring these nutrients to all ends of the plant. During the process of photosynthesis, water molecules combine with carbon derived from carbon dioxide to form glucose, which is the primary energy source of the vine, as well as oxygen as a by-product.[2]

In addition to its use in photosynthesis, a vine's water supply is also depleted by the processes of

humans and animals). The presence of adequate water in the vines can help keep the internal temperature of the leaf only a few degrees above the temperature of the surrounding air. However, if water is severely lacking then that internal temperature could jump nearly 18 °F (10 °C) warmer than the surrounding air which leads the vine to develop heat stress. The dual effects of evaporation and transpiration are called evapotranspiration.[2] A typical vineyard in a hot, dry climate can lose as much as 1,700 U.S. gallons (6,400 L; 1,400 imp gal) of water per vine through evapotranspiration during the growing season.[5]

Factors influencing irrigation

Climates with low humidity promote faster rates evapotranspiration which reduce the grapevine's water supply. These areas may need to utilize supplemental irrigation.

There are essentially two main types of irrigation; primary irrigation, which is needed for areas (such as very dry climates) that lack sufficient rainfall for viticulture to even exist, and supplemental irrigation where irrigation is used to "fill in the gaps" of natural rainfall to bring water levels to better numbers as well as to serve as a preventive measure in case of seasonal drought conditions. In both cases, both the climate and the

vineyard soils of the region will play an instrumental role in irrigation's use and effectiveness.[2]

Impact of different climate types

Viticulture is most commonly found in

Napa Valley only gets 2.4 inches (60 mm), on average, during the same period of time,[7]
often in an erratic pattern (some years seeing more, some years seeing only trace amounts of rain), and most appellations in Central and Southern California (both along the coast and inland) receive even less than that, necessitating supplemental irrigation.

Continental climates are usually seen in areas further inland from the coastal influences of oceans and large bodies of water. The difference from the average mean temperature of its coldest and hottest months can be quite significant with moderate precipitation that usually occurs in the winter and early spring. Depending on the water retaining ability of the soil the grapevine may receive enough water during this period to last throughout the growing season with little if any irrigation needed. For soils with poor water retention, the dry summer months may require some supplemental irrigation. Examples of continental climates that use supplemental irrigation include the

Argentina.[2]

Maritime climates tend to fall between Mediterranean and continental climates with a moderate climate that is tempered by the effects of a large body of water nearby. As with Mediterranean climates, the humidity of the particular macroclimate will play a significant role in determining how much irrigation is needed. In most cases irrigation, if it is used at all, will only be supplemental in years where drought may be an issue. Many maritime regions, such as

Oregon, suffer from the diametric problem of having too much rain during the growing season.[2]

Impact of different soil types

Sandy soils typically have poor water retention but good drainage. However, if its mixed with significant amounts of clay, such as this soil sample, its water retaining properties will increase while still draining well.

Soil can have a significant impact on the potential quality of wine. While

microbial agents that consume all the soil nutrients and end up starving the vine.[2]

The

South Australia. Depending on the climate and amount of natural rainfall, areas with poor water retention may need irrigation.[2]

Just as having too little water is detrimental to the grapevine, so too is having too much. When vines become water-logged they become a target for various microbial agents such as

earthworms and other organisms that have burrowed tunnels throughout the soil. Much like rocks, these tunnels give water a freer passageway through soil and contributes to its drainage.[2]

Measuring soil moisture

Tensiometers can be used to measure soil moisture. The components of this example include (1) porous cup, (2) water-filled tube (3) sensor-head and a (4) pressure sensor.
See also: Soil moisture sensor

Because of the problems associated with water-logged and wet soils, it is important for viticulturist to know how much water is currently in the soil before deciding if and how much to irrigate. Nowadays, precision agriculture uses high technology in the field, providing the producers with accurate measurements of the water needs of any specific vine. There are several methods of evaluating soil moisture. The most basic is simple observation and feeling of the soil, however this has its limitations since the

time-domain reflectometry and capacitance probes. In addition to monitoring for excessive moisture, viticulturists also keep an eye for signs of water stress (discussed below) due to severe lack of water.[2]

Irrigation systems

There are several methods of irrigation that can be used in viticulture depending on the amount of control and water management desired. Historically,

furrow irrigation system used in Argentina where small channels ran through the vineyard providing irrigation. This provide slightly more control since the initial amount of water entering the channels could be regulated, however the amount that each vine received was sporadic.[2]

Sprinkler irrigation involves the installation of a series of sprinkler units throughout the vineyard, often spaced as several rows about 65 feet (20 m) apart. The sprinklers can be set on an electronic timer and release predetermined amount of water for a set period of time. While this provides more control and uses less water than flood irrigation, like furrow irrigation the amount that each individual wine receives can be sporadic. The irrigation system that provides the most control over water management, though conversely the most expensive to install, is drip irrigation. This system involved long plastic water supply lines that run down each row of vines in the vineyard with each individual grape vine having its own individual dripper. With this system, a viticulturist can control the precise amount of water that each grapevine gets down to the drop. An adaption of this system, potentially useful in areas where irrigation may be banned, is underground subirrigation where precise measurements of water is delivered directly to the root system.[2]

Scheduling

See also: Irrigation scheduling
Water is very crucial during the early budding and flowering stages but after fruit set (pictured), the amount of water given to the vine may be scaled back in order to promote water stress.

With abundant water, a grapevine will produce shallow root systems and vigorous growths of new plant shoots. This can contribute to a large, leafy

physiologically ripe. With insufficient water, many of the vine's important physiological structures, including photosynthesis that contributes to the development of sugars and phenolic compounds in the grape, can shut down. The key to irrigation is to provide just enough water for the plant to continuing function without encouraging vigorous growth of new shoots and shallow roots. The exact amount of water will depend on a variety of factors including how much natural rainfall can be expected as well as the water retaining and drainage properties of the soil.[10]

Water is very crucial during the early

aromas.[12]

Water stress

See also: Deficit irrigation
One of the goals of controlled, mild water stress is to discourage the formation of excess new plant growths (a bud pictured) which will compete with the developing grape clusters for the vine's limited resources.

The term water stress describes the physiological states that grapevines experience when they are deprived of water. When a grapevine goes into water stress one of its first functions is to reduce the growth of new plant shoots which compete with the grape clusters for nutrients and resources. The lack of water also keeps the individual grape berries down to a smaller size which increase its skin to juice ratio. As the skin is filled with

France experience natural water stress due to the reduced rainfall that occurs during the summer growing season.[2]

At the far extreme is severe water stress which can have detrimental effects on both the vine and on potential wine quality. To conserve water, a vine will try to conserve water by limiting its loss through transpiration. The plant hormone

symptoms include:[12]

The effectiveness of water stress is an area of continuing research in viticulture. Of particular focus is the connection between yield size and the potential benefits of water stress. Since the act of stressing the vine does contribute to reduce photosynthesis-and by extension, reduce ripening since the sugars produced by photosynthesis is needed for grape development-it is possible that a stressed vine with high yields will only produce many under ripe grapes.

enologists and viticulturists such as Cornelius Van Leeuwen and Catherine Peyrot Des Gachons contending that white grape varieties lose some of their aromatic qualities when subjugated to even mild forms of water stress.[13]

Partial rootzone drying

In partial rootzone drying, half the roots are allowed to dehydrate which sends signals to the vine that is experiencing "water stress". Meanwhile, the irrigated roots on the other side of vine continue to provide sufficient amounts of water so that vital functions like photosynthesis does not cease.

One irrigation technique known as partial rootzone drying (or PRD) involves "tricking" the grapevine into thinking it is undergoing water stress when it is actually receiving sufficient water supply. This is accomplished by alternating drip irrigation to where only one side of the grapevine receives water at a time. The roots on the dry side of the vine produce abscisic acid that triggers some of the vine's physiological responses to water stress - reduced shoot growth, smaller berries size, etc. But because the vine is still receiving water on the other side the stress doesn't become so severe to where vital functions such as photosynthesis is compromised.[14] Partial rootzone drying has been shown to significantly increase a vine's water use efficiency. While PRD is shown to slightly reduce leaf area, this is generally not a problem as overall yield is unaffected.[15]

Criticism and environmental issues

See also:
Environmental impact of irrigation

The practice of irrigation has its share of criticism and environmental concerns. In many European wine regions the practice is banned under the belief that irrigation can be detrimental to quality wine production.

homogenization or "standardization" of wine.[12]

Other criticisms center around the broader environmental impact of irrigation on both the

A$3.6 million into research on how to minimize the damage caused by extensive irrigation.[17] In 2007, concerns about ecological damage to the Russian River caused government officials in California to take similar measures to cut back water supplies and promote more efficient irrigation practices.[18]

Other uses for irrigation systems

Drip irrigation systems can also be used to distribute controlled amounts of fertilization to the vines in a process known as "fertigation".

In addition to providing water for plant growth and development, irrigation systems can also be used for alternative purposes. One of the most common is the dual application of fertilizer with water in a process known as fertigation. Commonly used in drip irrigation systems, this method allows similarly regulate control over how precisely how much fertilizer and nutrients that each vine receives. Another alternative use for sprinkler irrigation systems can occur during the threat of winter or spring time frost. When temperature drop below 32 °F (0 °C), the vine is at risk of developing frost damage that could not only ruin the upcoming years harvest but also kill the vine. One preventive measure against frost damage is to use the sprinkler irrigation system to coat the vines with a protective layer of water that freezes into ice. This layer of ice serves as insulation keeping the internal temperature of the vine from dropping below the freezing mark.[2]

See also

References

  1. ^
    ISBN 0-7566-1324-8
  2. ^
    ISBN 0-19-860990-6
  3. ^ R. Joseph & J. Payne "Yves Benard: The new broom at the INAO Archived 2009-11-15 at the Wayback Machine" Meininger's Wine Business International, August 24, 2007
  4. ^ Think Quest Library "What is Irrigation? Archived 2012-10-19 at the Wayback Machine" Accessed: January 10, 2010
  5. ^ "Grapevine Water Relations" (PDF). Archived from the original (PDF) on June 1, 2010. Retrieved 2010-05-27.
  6. ^ "Climate of Florence, Italy".
  7. ^ "Climate of Napa, California".
  8. ^ C. Van Leeuwen & G. Seguin "The Concept of Terroir in Viticulture[permanent dead link]" Journal of Wine Research, 2006, Vol. 17, No. 1, pp. 1–10
  9. ^ A. Witze "Alcohol and science: The grapes of rock" Nature magazine volume 438 pp. 1073-1074 December 2005
  10. ISBN 0-932664-69-5
  11. ^ R. Gawel Is Irrigation Such a Bad Thing? An Australian Perspective Aroma Dictionary Wine Education Topics, Accessed: January 11, 2010
  12. ^
    ISBN 1-58017-105-2
  13. ^ C.P. Des Gachons, C. Van Leeuwen, et al "Influence of water and nitrogen deficit on fruit ripening and aroma potential of Vitis vinifera L cv Sauvignon blanc in field conditions" Journal of the Science of Food and Agriculture, Volume 85, Number 1, pp. 73-85 January 15, 2005
  14. ISBN 1-891267-91-4
  15. ^ Partial Rootzone Drying (PRD) Archived 2011-07-20 at the Wayback Machine
  16. ^ Harpers "INAO Signals Relaxation of AOC Irrigation Law Archived 2011-10-02 at the Wayback Machine" Harpers Wine & Spirits, December 1, 2004
  17. ^ Wines & Vines "Australian Plan to Stop Flood Irrigation" December, 2000
  18. ^ M. Greenspan "Water Cutbacks Drive Efficient Irrigation" Wine Business Monthly, July 15, 2007

Further reading

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