7. Canopy Management Flashcards
What are the six key aims of canopy management?
- Maximise the effectiveness of light interception by the vine canopy
- Reduce the shade within the canopy
- Ensure that the microclimate for the grapes is as uniform as possible so that grapes ripen evenly
- Promote balance between the vegetative and reproductive functions of the vine
- Arrange the vine canopy to ease mechanisation and/or manual labour
- Promote air circulation through the canopy to reduce incidence of disease.
How do buds exposed to sunlight develop differently to those subject to shady conditions?
- Exposure to sunlight is associated with greater bud fruitfulness, which describes the number of inflorescences developing inside a latent bud.
- Shady conditions are associated with reduced bud fruitfulness, with the bud producing more vegetative structures such as tendrils, rather than reproductive structures such as inflorescences.
How does sun exposure influence the development of the grape?
- Increased sugar levels in grapes through greater overall photosynthesis in the vine
- Increased tannin levels and greater polymerisation of those tannins, leading to less bitterness
- Enhanced anthocyanin (colour) development in black grapes
- Decreased malic acid
- Increased levels of some favourable aroma precursors compounds
- Decreased methoxypyrazines
Why do malic acid levels in grapes decrease with sun exposure?
Warmer grape temperatures lead to more malic acid being broken down in cellular respiration, otherwise, especially in cool climates, acidity levels in the wine could be unpleasantly high
What is undercropping, and how does it affect the vine’s cycle?
The yield of fruit is too low for the vigour of the vine.
- Shoot growth continues through the vine cycle because there is not much fruit to ripen.
- The growing shoots and leaves compete with the grapes for sugar and other compounds needed for growth and can negatively affect grape formation and ripening.
- Leads to a dense, shady canopy, and hence lower quality fruit due to lack of sunlight interception.
- Can lead to low yields the next year due to reduced bud fruitfulness, which can lead to under-cropping in that year and hence the vine enters what is known as ‘a vegetative cycle’.
What is overcropping and how does it affect the vine’s cycle?
The yield of fruit is too high compared to the vigour of the vine
The vine may gain sugars from the carbohydrates stored in the trunks, cordons and roots. The vine generally needs these carbohydrate sources in the winter and next spring, and too high a yield therefore weakens the vine in future years.
Describe a balanced cycle, where yields are balanced with vigour?
- Until véraison the vine’s sugars and nutrients are mainly allocated to shoot and root growth and storage.
- After véraison, sugars and other compounds needed for growth are mainly allocated to the fruit, and shoot growth is depressed.
- Because shoot growth is reduced, the canopy is less likely to become dense and shady, and light exposure in the canopy is improved, leading to high quality fruit.
- It also results in enhanced bud fruitfulness the next year, and the balanced cycle continues.
What are the natural factors that can influence the vine’s vigour?
- The growing environment; temperature and sunlight, water and nutrients
- Planting material; grape variety, clone, rootstock
- The presence of disease
- The age of the vine
How are yields measured?
A yield can either be measured per vine (e.g. kg per vine) or over a set area (e.g. kg per hectare or tons per acre).
What is vine density?
Vine density is the number of vines that are planted per hectare of vineyard.
What factors need to be considered when planning a vineyard’s vine density?
- Vine vigour
- The type of trellising system
- What access is needed between vines
What factors influence a grower’s decision on row orientation?
- Sunlight exposure
- Wind
- Slope
- Logistial efficiency
What is considered the best row orientation for even sunlight exposure?
It is generally considered that a north-south orientation provides the most even sunlight exposure through the canopy.
Bunches on the west side of the canopy (which are exposed to the afternoon sun) may require more shading from leaves to protect them from sunburn.
How might prevailing winds be a factor in decisions on row orientation?
Grape growers choosing to orient the rows at a 90° angle to the direction of the wind to provide most protection.
How does a sloped vineyard influence decisions on row orientation?
Vineyards on slopes at an angle of greater than 10% need to be planted up and down the slope rather than across or machinery may slip (unless the vineyard is terraced).
What factors need consideration when planning a vineyard’s training and trellising method?
- The vigour of the vine
- The topography of the site
- The need for mechanisation
What are the two categories of vine training?
Head training; can either be spur-pruned or replacement cane-pruned.
Cordon training; usually spur pruned
Why is winter pruning important?
It determines the number and location of buds that will form shoots in the coming growing season, and hence impacts on the potential yield.
Why does cordon training take longer to establish than head training?
The amount of permanent wood required
What is spur pruning?
- Spurs are short sections of one-year-old wood that have been cut back to only two or three buds.
- Spurs can either be distributed along a cordon or around the top of the trunk.
- Spur pruning is easier to carry out than replacement cane pruning and can often be mechanised.
What is replacement cane pruning?
- Canes can have anything between 8 and 20 buds.
- They are typically laid down horizontally and need tyingto a trellis for support and positioning.
- Replacement cane pruning is more complex than spur pruning and requires a skilled labour force to select suitable canes and train them.
What are the benefits of bush vines?
- Simple and inexpensive to develop
- Shoots may droop down and provide shade for grapes; beneficial in hot, sunny climates.
How are bush vines typically trained and pruned?
Head trained, spur pruned
What are the disadvantages of bush vines?
- Not suitable for mechanisation
- The risk of the canopy becoming too dense (leading to too much shading) if the vigour is too high
- Wet conditions would promote development of disease
What are the advantages of trellising?
- The shoots can be spread out to maximise light interception
- Increase air flow through the canopy (reducing risk of fungal disease)
- By positioning the fruit in one area, aid mechanisation.
What are the disadvantages of trellising?
Extensive to establish and require maintenence
Describe vertical shoot positioning (VSP).
- The vine’s shoots are trained vertically and are held in place onto the trellis forming a single narrow canopy.
- It can be used on both head-trained, replacement cane-pruned vines and cordon-trained, spur-pruned vines
What is guyot training?
Replacement cane pruned vines with vertical shoot positioning (VSP)
Single guyot; one cane
Double guyot; two canes
Is vertical shoot positioning (VSP) more suitable for low-moderate or high vigour vines?
Low-moderate
Why are vines with high vigour not suited for vertical shoot positioning?
Vines that are vigorous can produce a lot of shoots and ripen high yields of fruit. If these vines are trellised using VSP, the canopy can be too dense, resulting in too much shading of leaves and fruit.
How is this vine trained, pruned and trellised?
Head trained
Replacement cane pruned
Vertical shoot positioning
How is this vine trained, pruned and trellised?
Cordon trained
Spur pruned
Vertical shoot positioning
What is the name of this trellising system?
Double geneva curtain
What is the name of this trellising system?
Lyre
What is the name of this trellising system?
Scott-Henry
What are the aims of summer pruning?
- Enhancing grape ripening
- Reducing chance of fungal disease (increasing aeration in the canopy)
- Making the vineyard easier to manage (mechanisation etc)
What are the aims of disbudding?
- To adjust the number of buds to bring the vine into balance (and/or to comply with local growing laws).
- Remove buds that are poorly positioned (eg, those facing downwards or those too close together. )
- To remove buds of non-fruit-bearing shoots, which may compete with the grapes for sugar and other resources.
Why is disbudding typically done in spring/summer rather than winter?
Growers will often leave a high number of buds on the vine at winter pruning in case buds are damaged early in the growing season, for example, by spring frost.
What are the aims of shoot removal?
The removal of shoots, often laterals, that are infertile or poorly positioned (e.g. too close together or low down on the trunk) will help to maintain a well-organised, open canopy.
What are the aims of shoot positioning?
The shoots are tucked into the trellis wires to better organise the canopy and facilitate mechanisation.
What is the aim of pinching?
This removes the shoot tips at flowering to improve fruit set.
What are the aims of shoot trimming?
Cutting shoots to limit growth and reduce canopy thickness enhances fruit ripening by reducing competition for carbohydrates between the shoot tips and fruit. It also lowers disease pressure through better air circulation and improved spray penetration.
What are the aims of leaf removal?
Removing leaves to reduce shading of fruit and hence enhance ripening, will also lower disease pressure through better air circulation and improved spray penetration.
What is the risk of leaf removal?
In warm and hot climates, excessive removal of leaves can expose the grapes to too much sunshine and heat and lead to sunburn.
What is crop thinning/green harvesting?
This is the removal of bunches of grapes to increase ripeness of those grapes left on the vine.
What are the aims of crop thinning/green harvesting?
If this process is timed near véraison, it can enhance ripening. In cases where fruit ripening is uneven (e.g. because of uneven budburst or fruit set, frost or the presence of bunches on lateral shoots), the least ripe bunches of grapes may be removed to improve uniformity of ripening, and hence enhance quality.
