D1C06 Managing Nutrients + Water

Question 1

Define soil health within grape growing.

Answer 1

Within grape growing, soil health is the ability of the soil to support the vine, enabling it to grow and produce fruit.

Question 2

Vines gain the water and nutrients that they need to survive, grow and produce fruit from the soil. Ensuring the soil is healthy is therefore seen as a vital part of good vineyard management.
What 4 factors determine soil health?

Answer 2

the structure of the soil: good drainage, sufficient water-holding capacity, sufficient oxygen, the ability to resist erosion and to allow the roots of the vine to penetrate to sufficient depth
the amount of organic matter and humus in the soil: decomposing organic matter supplies nutrients, and humus improves the structure of soil and its water-holding capacity
the number of living organisms in the soil: earthworms and microbes break down organic matter into humus and inorganic nutrients that are accessible to the vine
the total amount of available nutrients that the vine needs to grow successfully

Question 3

What are the effects of poor soil health?

Answer 3

Poor soil health can lead to problems with the availability and uptake of nutrients and water in the soil, and hence poor vine growth and ripening.
Grape growers may have the soil tests conducted when establishing the vineyard and then annually so that corrective measures can be taken.

Question 4

There are several methods that can be used during the growing season to control the level of nutrients in the soil and their accessibility to the vine.
Name 6 of these methods…

Answer 4

1. Application of fertilizers
2. Cultivation
3. Herbicides
4. Animal grazing
5. Cover crops
6. Mulching

Question 5

Next to influencing accessibility of water as well as nutrients, for what additional reasons are weeds removed?

Answer 5

1. Bare, moist soils are best at absorbing heat during the day and the heat they release at night reduces frost risk. By comparison, weeds, as well as cover crops and mulches, can therefore increase frost risk.
2. Some weeds also hamper the passage of machinery and personnel (e.g. stinging nettles, brambles).

Question 6

What are the 2 main reasons for the application of fertilizers?

Answer 6

Fertilisers may be added before planting to help the growth of young vines. They may also be applied to established vineyards to correct any detected nutrient deficiencies.

Question 7

What is the effect of excessive addition of fertilizers?

Answer 7

Excessive addition of fertilisers may lead to excess vigour and an unbalanced vine

Question 8

Where are organic fertilizers derived from?

Answer 8

Organic fertilisers are derived from fresh or composted plant or animal material, such as manure or slurry. Or from green manure.

Question 9

Define green manure…

Answer 9

Cover crops or natural vegetation that are grown and mown into the soil to decompose and provide nutrients.

Question 10

What are the advantages of using organic fertilizers?

Answer 10

Organic fertilisers are often cheap or even free.
Some are high in humus and therefore good for soil structure and water retention.
As their nutrients tend to be in organic form, they provide nutrition for soil organisms, promoting the living matter in the soil.
The nutrients become available to the vine gradually, which can be an advantage.

Question 11

What are the disadvantages of using organic fertilizers?

Answer 11

Because the organic nutrients need to be broken down into inorganic nutrients by these organisms, these fertilisers require incorporation into the soil, which requires labour.
A disadvantage is that they can be bulky and therefore expensive to transport and spread.

Question 12

What are the advantages of using mineral fertilizers?

Answer 12

They can provide a single nutrient or several nutrients; therefore, they can be more tailored than organic fertilisers.
The nutrients are already in an inorganic form and therefore can be more readily available to the vines than organic fertilizers.
They are more concentrated, much cheaper to transport and distribute than organic fertilizers.

Question 13

What are the disadvantages of using mineral fertilizers?

Answer 13

They hold no benefit for soil organisms and do not improve soil structure as organic fertilizers do.
They are often more expensive than organic fertilisers to purchase.

Question 14

Define cultivation…

Answer 14

Cultivation is a method of weed control that involves ploughing the soil to cut or disturb the weeds’ root systems.

Question 15

What are the 2 advantages of cultivation?

Answer 15

This method does not use any chemicals and so can be used in organic and biodynamic viticulture.
It enables fertiliser and, where relevant, mown cover crops to be incorporated into the soil at the same time as removing weeds.

Question 16

What are the 4 disadvantages of cultivation?

Answer 16

Repeated cultivation can damage the soil’s structure and ecology due to the breakdown of organic matter and destruction of habitats.
It is costly as it requires both skilled labour and machinery.
Disturbing the soil buries seeds, thus encouraging the weeds to grow back.
It can increase vine vigour too much as there is no competition for water or nutrients (not necessarily a disadvantage in low vigour sites (poor soils and/or lack of water)).

Question 17

Define herbicides….

Answer 17

Herbicides are chemical sprays that kill weeds. There are three types of herbicides:

Question 18

What are the 3 types of herbicides used?

Answer 18

1. Pre-emergence herbicides are sprayed before weeds establish. They persist in the surface layers of the soil, but are absorbed by the weeds’ roots and inhibit germination of young seedlings.
2. Contact herbicides are sprayed on established weeds and kill the green parts of the weed that they contact.
3. Systemic herbicides are sprayed on established weeds and are taken in by the leaves. The herbicide travels up and down the weed in the sap and kills the whole plant.

Question 19

What are the 3 advantages of herbicides?

Answer 19

They are cheap in terms of labour and machinery requirements.
They are highly effective, particularly in the under-row area.
They are less damaging to the soil structure than cultivation.

Question 20

What are the 4 disadvantages of herbicides?

Answer 20

They present the risks of poisoning to the operator, consumer and environment, and do not encourage vineyard ecosystems.
Weeds can become resistant and therefore larger doses or different chemicals need to be used. The routine use of glyphosate, the most common contact herbicide, in South Africa and elsewhere has given grape growers a particular problem with glyphosate-resistant ryegrass.
They can increase vine vigour too much as there is no competition for water or nutrients (not necessarily a disadvantage in low vigour sites).
They are not allowed in organic and biodynamic viticulture.

Question 21

Define animal grazing…

Answer 21

Another method of weed control is to allow animals, such as sheep, to graze in the vineyard.

Question 22

What are the 3 advantages of animal grazing?

Answer 22

This method does not use any chemicals and so can be used in organic and biodynamic viticulture.
The animals can provide the vineyard with manure.
The animals can be a source of meat for humans.

Question 23

What are the 3 disadvantages of animal grazing?

Answer 23

The vines must be trained suitably high or the grazing must be conducted out of growing season, otherwise the animals may eat leaves and grapes off the vines.
The animals need caring for if they belong to the vineyard owners, which requires labour.
The animals are often susceptible to vineyard pesticides.

Question 24

Define cover crops in the context of wine growing…

Answer 24

Cover crops are plants that are specifically planted, or allowed to grow, that have a beneficial effect on the vineyard.
Cover crops that are quick to establish and are adapted to the soil and climatic conditions are best. Cover crops are widely used around the world, but have to be matched to the needs of the vineyard.

Question 25

Name 6 beneficial effects achieved through the use of cover crops…

Answer 25

Cover crops may be grown to suppress weeds. They may also be planted to improve soil structure, compete with the vine for nutrient and water availability in fertile sites, manage soil erosion, enhance biodiversity and provide a surface to drive on.

Question 26

Why are cover crops sometimes more desired than leaving natural vegetation?

Answer 26

It is also possible to leave natural vegetation to grow in the vineyard to achieve any of the benefits of cover crops. Although this is cheap, and can permit greater diversity, specific cover crops with known characteristics allow more control.

Question 27

What are the 3 advantages of cover crops?

Answer 27

This method does not use any chemicals and increases soil biological activity and biodiversity in the vineyard, so is commonly used in organic and biodynamic viticulture.
The ability to influence the vigour of the vine by introducing competition for water and nutrients.
The provision of a good surface for machinery, particularly in climates with high annual rainfall.

Question 28

What are the 3 disadvantages of cover crops?

Answer 28

A reduction in vine vigour (through competition for water and nutrients) that can be excessive in poor soils and dry environments.
The difficulty of mowing the under-row area, particularly near the vine trunks, which has implications on time and labour.
The unsuitability for steeply-sloping vineyards, as they are slippery when wet.

Question 29

Define mulching…

Answer 29

Mulching is the spreading of matter onto the vineyard soil to suppress the growth of weeds.
Mulches are usually made of biodegradable materials, such as straw or bark chips, that ultimately provide nutrients for the vines. Materials with a high nutrient content can be chosen in nutrient-poor vineyards.

Question 30

What are the 3 advantages of mulching?

Answer 30

This method does not use any chemicals, so can be used in organic and biodynamic viticulture.
It can reduce water evaporation from the soil, which can be advantageous in dry climates.
It can ultimately be a source of nutrients and humus, which promotes soil biological activity and good soil structure.

Question 31

What are the 3 disadvantages of mulching?

Answer 31

Mulch tends to be very bulky, and so expensive to transport and spread.
It is only effective if applied in a thick layer, so a lot can be needed.
It can increase vigour too much as there is no competition for water or nutrients (not necessarily a disadvantage in low vigour sites).

Question 32

Under what conditions is irrigation necessary?

Answer 32

If the new vineyard is located in an area that is likely to receive very little water through the growing season, or has very free-draining soils, irrigation may be necessary and should be a part of vineyard design and establishment.
Not that irrigation systems can be fitted in an established vineyard if the need is persistent, but this can be much more difficult because of potential disruption to the vineyard in order to lay pipes.

Question 33

What could be reasons for not using irrigation, even-though very little (rain)water is received through the growing season?

Answer 33

It must be noted that some EU GIs do not permit irrigation or only allow it for emergency situations (establishing young vines, drought that threatens the livelihood of grape growers).In other cases, difficulty in sourcing water for irrigation may mean that it cannot be used.

Question 34

What are the typical sources of water for irrigation?

Answer 34

Water for irrigation can come from many sources, such as a nearby river, lake, reservoir or bore-hole. However, water is a precious resource and therefore in many countries water use is tightly regulated.

Question 35

Australia, California and South Africa have experienced extreme shortages in water supply in recent times resulting from prolonged periods of dry weather. Therefore, for sustainability, it is important to increase the efficiency of water use.
What 6 steps can taken in the vineyard?

Answer 35

use of certain water-efficient irrigation systems and techniques combined with better monitoring of water take-up by the vines (e.g. dripper systems and regulated deficit irrigation)
use of drought-tolerant grape varieties (e.g. Grenache), and rootstocks (e.g. 140R)
reducing evaporation (e.g. by applying a mulch)
reducing competition (e.g. removing weeds)
increasing humus levels in the soil to improve water retention (e.g. by adding organic matter such as compost)
promoting the growth of vine roots deep into the soil (e.g. through cultivation)

Question 36

What can be the effect of (irrigation) water with a high salinity, as is the case in many areas in Australia?

Answer 36

This water increases salt levels in the soil and makes it more difficult for vine roots to take up water. The vine becomes dehydrated and the green parts of the vine start to wilt and eventually die. This is particularly a problem when drip irrigation is used, as the salt accumulates at the root zone, rather than being washed deeper into the soil, for example by flood irrigation.

Question 37

Describe a (typical) drip irrigation system |infrastructure…

Answer 37

Drip irrigation is by far the most common type of irrigation used in vineyards. Thin water pipes are laid along each row, typically tied to the lowest trellis wire. Drippers are fitted at appropriate intervals. The drippers are positioned far enough away from the vines to encourage the roots to grow and seek out water.
(If the drippers are positioned near to the vine trunk, the roots will simply collect near the trunk where the water falls.)

Question 38

What are the 4 advantages of drip irrigation systems?

Answer 38

they permit an economic use of water
it is possible to control water supply to individual rows or blocks of vines, allowing more tailored management of the vineyard and thus potentially higher yields and quality
they can also be used to supply fertiliser (liquid fertiliser is added to the water supply); this is called fertigation
they can be used on slopes.

Question 39

What are the 4 disadvantages of drip irrigation systems?

Answer 39

installation costs are relatively high, but maintenance costs are moderate
clean water is required, otherwise the drippers quickly become blocked
the drippers can gradually become blocked by algae, bacteria or high levels of minerals and salts; therefore, some maintenance work is usually required
they cannot be used in frost protection (aspersion) as the drippers are below the upper parts of the vine.

Question 40

Explain flood irrigation…

Answer 40

In flood irrigation, water is stored behind a sluice and at the scheduled time released to flood the vineyard.

Question 41

What are the advantages & disadvantages of flood irrigation?

Answer 41

It is cheap to install and maintain, but is inefficient as a lot of the water is not taken up by the vine. It can also only be used on flat or gently sloping land. They are not suitable where water supply is limited.

Question 42

Explain channel irrigation…

Answer 42

Channel irrigation is similar to flood irrigation; however, the water flows down furrows dug between the vine rows, which can help increase efficiency of water use.

Question 43

In which wine region are flood- and channel-irrigation typical used?

Answer 43

These systems are common in Argentina because of abundant water from the Andes.

Question 44

Explain overhead sprinklers…

Answer 44

Overhead sprinklers pump water and shower it over the vineyard.

Question 45

What are the advantages & disadvantages of overhead sprinklers?

Answer 45

They are expensive to install and maintain due to high water pressures needed and still use a relatively large amount of water compared to drip irrigation. However, they can be used as a method of frost protection.

Question 46

What is DFI?

Answer 46

Regulated deficit irrigation (RDI),

Question 47

Explain how Regulated deficit irrigation (RDI) works…

Answer 47

RDI is a system of timing and regulating the amount of irrigation so that the vine is put under mild to moderate water stress for a specified time within the growing season. A dripper system is used to permit best control over application of water.
This water deficit is usually scheduled between fruit set and véraison to limit further shoot growth and encourage grape development.

Question 48

Describe the effect of different soil types on the effectiveness of RDI…

Answer 48

RDI is easiest in regions with a dry growing season and sandy or loam soils that dry out and can be re-wetted quickly.
It can be much more difficult to create the ideal conditions in regions with heavy rainfall in spring and/or frequent rain in the growing season, and with heavy clay soils that take a long time to dry out.

Question 49

Why is RDI often favoured for black grapes?

Answer 49

This RDI regime can reduce grape size, which increases the proportion of skins to juice, and hence increases the concentration of anthocyanins and tannins, often seen as a sign of quality.
It often results in lower yields, and therefore the grape grower must be confident that any improvements in grape quality will make up for smaller volumes

Question 50

Define ‘dry farming’…

Answer 50

Some grape growers do not use irrigation; this may or may not be through choice. This practice is often called ‘dry farming’ and tends to refer to not using irrigation in areas with limited rainfall in the growing season (rather than not using irrigation because there is plentiful rainfall). Similar to limiting the amount of water in irrigation, this can lead to lower yields but potentially an improvement in grape quality.

Question 51

When are drainage systems used?

Answer 51

Some vineyard areas receive plentiful rainfall, and if the soils are not suitably free draining, this can cause a number of problems. In these cases, artificial drainage systems may need to be installed.

Question 52

Give 2 methods to regulate the water available to the vine (in areas with high rainfall in the growing season)….

Answer 52

leaving natural vegetation to grow or planting specific crops to provide competition for water, leaving less available for the vine
improving soil structure and removing any plough plans to better regulate water drainage