6. Managing Nutrients and Water Flashcards

1
Q

What does the term ‘soil health’ refer to?

A

The continued capacity of the soil to act as a living ecosystem that sustains plants, animals and humans.

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2
Q

What factors determine the health of soil?

A
  • Soil structure
  • The amount of organic matter and humus
  • The number of living organisms present
  • The amount of available nutrients
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3
Q

What properties of a soil’s structure influence the general health of the soil?

A
  • Good drainage
  • Sufficient water holding capacity
  • Sufficient oxygen
  • The ability to resist erosion
  • To allow the roots of the vine to penetrate to a sufficient depth
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4
Q

When is a vineyard’s soil typically tested? Why?

A

Grape growers may have soil tests conducted when establishing the vineyard and then annually so that corrective measures, such as improving the structure of the soil or adjusting nutrient levels, can be taken.

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5
Q

Why are organic matter and humus important for soil health?

A

Decomposing organic matter supplies nutrients, and humus improves the structure of soil and its water-holding capacity

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6
Q

Why are living organisms important for soil health?

A
  • Earthworms and microbes break down organic matter into humus and inorganic nutrients that are accessible to the vine
  • Ecosystem services
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7
Q

What are the six methods of managing nutrients in the vineyard?

A
  1. Fertilisers; organic or inorganic
  2. Cultivation; weed management
  3. Herbicides; weed management
  4. Animal grazing
  5. Cover crops
  6. Mulching
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8
Q

What are organic fertilisers?

A

Organic fertilisers are derived from fresh or composted plant or animal material (manure or slurry)

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9
Q

What is green manure?

A

Green manure is produced by cover crops that have been grown, mown and turned into the soil to decompose and provide nutrients

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10
Q

What are the advantages of organic fertilisers?

A
  • Cheap or sometimes free
  • Some are high in humus, 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.
  • Become available to the vine gradually (while organisms in the soil break down organic fertiliser to inorganic).
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11
Q

What are the disadvantages of organic fertilisers?

A
  • More labour required to incoperate into the soil for it to be broken down (converted by soil organisms to inorganic fertiliser).
  • Can be bulky and difficult to transport
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12
Q

What are inorganic fertilisers?

A

Inorganic fertilisers, also called synthetic fertilisers, are manufactured from minerals extracted from the ground or synthetic chemicals. They can provide a single nutrient or several nutrients.

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13
Q

What are the advantages of inorganic fertilisers?

A
  • They can provide a single nutrient or several; so can be tailored to the soil’s needs
  • Already in inorganic form, readily available to the vine once applied
  • Cheaper to transport and distribute compared to organic fertilisers
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14
Q

What are the disadvantages of inorganic fertilisers?

A
  • They hold no benefit for soil organisms and do not improve soil structure
  • More expensive to purchase than organic fertilisers
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15
Q

What is cultivation?

A

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

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16
Q

What are the advantages of cultivation?

A
  • 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.
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17
Q

What are the disadvantages of cultivation?

A
  • Repeated cultivation can damage the soil’s structure and ecology due to the breakdown of organic matter and disruption of earthworms in their habitat.
  • 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)).
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18
Q

What are the three types of herbicides?

A
  • Pre-emergence herbicides
  • Contact herbicides
  • Systemic herbicides
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19
Q

How do pre-emergence herbicides work?

A

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.

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20
Q

How do contact herbicides work?

A

Contact herbicides are sprayed on established weeds and kill the green parts of the weed that they contact, resulting in the death of the plant.

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21
Q

How do systemic herbicides work?

A

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.

22
Q

What are the advantages of herbicides?

A
  • 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.
23
Q

What are the disadvantages of herbicides?

A
  • 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.
  • 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.
24
Q

Give an example of weed’s becoming resistant to herbicides.

A

The routine use of glyphosate, one of the most common herbicides, in South Africa and elsewhere has given grape growers a particular problem with glyphosate-resistant ryegrass.

25
Q

What are the advantages of animal grazing in the vineyard?

A
  • 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.
26
Q

What are the disadvantages of animal grazing in the vineyard?

A
  • 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.
27
Q

What are the reasons a grower may choose to plant cover crops?

A
  • Weed suppression
  • Improve soil structure
  • Create competition with the vines for water and nutrients
  • Manage soil erosion
  • Enhance biodiversity
  • Provide a surface to drive on for mechanisation
28
Q

What are the main types of cover crops used?

A

Legumes and grasses

29
Q

How does the choice in cover crops assist in fixing nitrogen levels in the soil?

A

Legumes are known to increase nitrogen in the soil due to their role in fixing air nitrogen in their roots, whereas grasses scavenge the soil’s nitrogen.

30
Q

What are the advantages of cover crops?

A
  • Method does not use any chemicals
  • Increases soil biological activity and biodiversity in the vineyard
  • 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.
31
Q

What are the disadvantages of cover crops?

A
  • 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.
32
Q

What is mulching?

A

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.

33
Q

What are the advantages of mulching?

A
  • 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.
34
Q

What are the disadvantages of mulching?

A
  • Mulch tends to be very bulky, and therefore is 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).
35
Q

What are the two main elements involved in the water management of a vineyard?

A

Irrigation
Drainage

36
Q

What steps can be taken to increase efficiency of water use?

A
  • 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 and rootstocks
  • Reducing evaporation
  • Reducing competition
  • Increasing humus levels in the soil to improve water retention
  • Promoting the growth of vine roots deep into the soil
37
Q

What risk does water that is high in salt (high salinity) pose for vines?

A

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.

38
Q

How are drip irrigation systems installed and why?

A

Narrow 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.)

39
Q

What are the key benefits of drip irrigation systems?

A
  • 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 (fertigation)
  • They can be used on slopes.
40
Q

What is fertigation?

A

Liquid fertiliser is added to the water supply in irrigation systems

41
Q

What are the disadvantages of drip irrigation systems?

A
  • Installation costs are relatively high, but maintenance costs are moderate
  • Clean water is required, otherwise the drippers quickly become blocked
  • Even with clean water, 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 green parts of the vine.
42
Q

What is flood irrigation?

A

Water is stored behind a sluice and at the scheduled time released to flood the vineyard.

43
Q

What is channel irrigation?

A

Water is stored behind a sluice and at the scheduled time released allowing the water to flow down furrows dug between the vine rows.

44
Q

What are the four methods of irrigation?

A
  • Drip irrigation
  • Flood irrigation
  • Channel irrigation
  • Overhead sprinklers
45
Q

What country are channel irrigation systems commonly used and why?

A

Argentina; because of abundant water from the Andes.

46
Q

What are the disadvantages of using overhead sprinklers as an irrigation method?

A
  • They are expensive to install and maintain due to the high water pressures needed
  • They use a relatively large amount of water compared to drip irrigation.
47
Q

What is regulated deficit irrigation (RDI)?
When and why is it typically used?

A

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.

The water deficit is usually scheduled between fruit set and véraison to limit further shoot growth and encourage grape development.

A dripper system is used to permit best control over application of water.

48
Q

What are the main benefits of using a regulated deficit irrigation (RDI)?

A

Vine growth and grape development can be better controlled and that less water can be used.

49
Q

Why are regulated deficit irrigation (RDI) systems favoured for black grapes?

A

It 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.

50
Q

What are the disadvantages and risks of regulated deficit irrigation (RDI) systems?

A
  • Difficult to use 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.
  • Timing of water application and monitoring of soil water levels is critical; prolonged or extreme water stress can lead to reduction in yield and quality.
  • Often results in lower yields; improvements in grape quality must make up for smaller volumes.
  • The additional costs of the equipment to monitor and respond to levels of moisture in the soil.
51
Q

What is dry farming?

A

Refers to not using irrigation in areas with limited rainfall in the growing season

52
Q

In areas with high rainfall, how can a grower regulate the water available to the vine?

A
  • Install artificial drainage systems (before the vineyard is planted).
  • Leave natural vegetation to grow or planting specific crops to provide competition for water, leaving less available for the vine.
  • Improve soil structure and removing any plough pans to better regulate water drainage