6.2 Nutrient Management

Question 1

What types of techniques are used to control the level of nutrients in the soil and their accessibility to the vine?

Answer 1

• Direct application of nutrients
• Promotion of biological activity and soil structure
• Weed management

Question 2

Why are weeds bad for vines?

Answer 2

• Compete with the vine for nutrients
• Can increase frost risk because they prevent soils from asborbing max heat during the day
• Hamper the passage of machinery and personnel

Question 3

What are fertilizers? When are they applied? What are the two types?

Answer 3

• Types: organic or mineral
• Added before planting to help the growth of young vines
• Applied to established vineyards to correct any detected nutrient deficiencies

Question 4

What are organic fertilizers derived from? Give some examples.

Answer 4

• Derived from fresh or composted plant or animal material
• Ex: manure or slurry
• Ex: Cover crops can be grown and mown into the soil to decompose and provide nutrients

Question 5

What are the advantages of organic fertilizers?

Answer 5

• Cheap or sometimes free
• If high in humus, can be good for soil structure and water retention
• Provide nutrition for soil organisms and promote living matter in soil

Question 6

What are the disadvantages of organic fertilizers?

Answer 6

• Requires labour - because the organic nutrients need to be broken down into inorganic nutrients by these organisms, these fertilisers require incorporation into the soil
• Can be bulky - expensive to transport and spread

Question 7

What are mineral fertilizers?

Answer 7

• Extracted from the ground or chemically manufactured

Question 8

What are the advantages of mineral fertilizers?

Answer 8

• can be more tailored than organic fertilisers (single or several nutrients)
• Already in an inorganic form can be readily available to the vines
• More concentrated, cheaper to transport and distribute

Question 9

What are the disadvantages of mineral fertilizers?

Answer 9

• Hold no benefit for soil organisms
• Do not improve soil structure
• Can be expensive

Question 10

What is cultivation?

Answer 10

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

Question 11

What are the advantages of cultivation?

Answer 11

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

Question 12

What are the disadvantages of cultivation?

Answer 12

1. Repeated cultivation can damage the soil’s structure and ecology due to the breakdown of organic matter and destruction of habitats.
2. It is costly as it requires both skilled labour and machinery.
3. Disturbing the soil buries seeds, thus encouraging the weeds to grow back.
4. 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 13

What are herbicides?

Answer 13

Chemical sprays that kill weeds

Question 14

What are the 3 types of herbicides?

Answer 14

1. Pre-emergence herbicides
2. Contact herbicides
3. Systemic herbicides

Question 15

When are pre-emergence herbicides sprayed? What do they do?

Answer 15

• 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.

Question 16

When are contact herbicides sprayed? What do they do?

Answer 16

• Sprayed on established weeds

- Kill the green parts of the weed that they contact

Question 17

When are systemic herbicides sprayed? What do they do?

Answer 17

• sprayed on established weeds

- Taken in by the leaves, travels up and down the weed in the sap and kills the whole plant

Question 18

Name 3 advantages of herbicides.

Answer 18

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

Question 19

Name 4 disadvantages of herbicides.

Answer 19

1. They present the risks of poisoning to the operator, consumer and environment, and do not encourage vineyard ecosystems.
2. Weeds can become resistant and therefore larger doses or different chemicals need to be used.
3. They can increase vine vigour too much as there is no competition for water or nutrients (not necessarily a disadvantage in low vigour sites).
4. They are not allowed in organic and biodynamic viticulture.

Question 20

Give an example of a region and a herbicide to which weeds have become resistant.

Answer 20

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.

Question 21

What are the 5 main methods of weed control?

Answer 21

1. Herbicides
2. Animal Grazing
3. Cover Crops
4. Cultivation
5. Mulching

Question 22

What is animal grazing?

Answer 22

A method of weed control where animals, such as sheep, are allowed to graze in the vineyard

Question 23

Name 3 advantages of animal grazing.

Answer 23

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

Question 24

Name 3 disadvantages of animal grazing.

Answer 24

1. 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.
2. The animals need caring for if they belong to the vineyard owners, which requires labour.
3. The animals are often susceptible to vineyard pesticides

Question 25

What are cover crops?

Answer 25

Plants that are specifically planted, or allowed to grow, that have a beneficial effect on the vineyard

Question 26

Name 6 reasons why might cover crops might be used.

Answer 26

1. Grown to suppress weeds
2. Planted to improve soil structure
3. Compete with the vine for nutrient and water availability in fertile sites
4. Manage soil erosion
5. Enhance biodiversity
6. Provide a surface to drive on

Question 27

Give some examples of cover crops.

Answer 27

• Legumes (such as beans and clover)

- Cereals (such as ryegrass and oats)

Question 28

How does a grape grower choose which cover crops to plant? Name an organization that helps with this.

Answer 28

• Cover crops should be matched to the needs of the vineyard
• Certain cover crops with known characteristics allow more control
• Wine Australia

Question 29

Why might a grape grower choose to leave natural vegetation to grow in the vineyard?

Answer 29

• Cheap

- Permits greater diversity

Question 30

Why must a cover crop be managed carefully?

Answer 30

Ensure it does not compete too much with the vine for water and nutrients at key times in the vine cycle

Question 31

What is green manure?

Answer 31

If ploughed into the soil, the cover crop or natural vegetation can provide organic matter and fertilise the soil.

Question 32

Name 3 advantages of using cover crops.

Answer 32

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

Question 33

Name 3 disadvantages of using cover crops.

Answer 33

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

Question 34

What is mulching?

Answer 34

The spreading of matter onto the vineyard soil to suppress the growth of weeds

Question 35

What are mulches typically made of?

Answer 35

Biodegradable materials, such as straw or bark chips

Question 36

Name 3 advantages of mulching.

Answer 36

1. Does not use any chemicals; can be used in organic and biodynamic viticulture.
2. Reduces water evaporation from the soil, which can be advantageous in dry climates.
3. Source of nutrients and humus, which promotes soil biological activity and good soil structure.

Question 37

Name 3 disadvantages of mulching.

Answer 37

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