6. Managing Nutrients + Water

Question 1

What are (4) advantages/ (2) disadvantages of organic fertilizers?

Answer 1

AD - cheap/free

• high in humus = good for soil structure + water retention.
• provide nutrition for soil organisms.
• Nutrients become available for soil more gradually = longer lasting.

DIS - they need to be broken down into inorganic = requires incorporation into soil = labour/cost.

• Bulky = expensive to transport/spread.

Question 2

What are (4) disadvantages of cultivation as a method of weed control?

Answer 2

• repeated = can damage soil’s structure/ecology via breakdown of organic matter/destruction of habitats.
• requires skilled labor + machinery = costly
• can increase vigour too much (no competition)
• can actually bury seeds, encouraging weeds to grow back.

Question 3

Why is it advantageous for grape growers to remove weeds from the vineyard (3)?

Answer 3

• Weeds compete with vines for resources (water/nutrients)
• Weeds can increase risk of frost by blocking heat that would be absorbed by soils.
• Weeds can impede machinery/personnel (e.g. stinging nettles)

Question 4

Why would artificial drainage channels need to be installed in a vineyard?

When does this need to be done?

What are advantages to this practice (2)?

Answer 4

• Vineyard receives plentiful rainfall but soils are not free-draining (like gravel soils in Médoc are.)
• Must be done before vineyard is planted.
  1) Healthier, better balanced vines that ripen fruit consistently.
  2) Aids mechanization by providing better driving surface.

Question 5

What are disadvantages of drip irrigation (4)?

Answer 5

• high installation costs
• clean water required to prevent blockage
• drippers can become blocked anyway by algae/minerals/bacteria/salt = more maintenance.
• cannot be used in frost protection (drippers are below upper parts of vine)

Question 6

What are (2) advantages of cultivation as a means of weed control?

Answer 6

• doesn’t use chemicals (suitable for organic / biodynamic)
• enables cover crops to be incorporated into soil at same time as removing weeds.

Question 7

What is the source of mineral fertilizers?

What is their purpose?

Answer 7

• Extracted from the ground or chemically manufactured.
• Purpose is to provide a single nutrient or several nutrients lacking in the soil.

Question 8

What are 3 types of herbicides?

Answer 8

1) pre-emergence: sprayed before weeds establish and persist on surface of soil
2) contact: sprayed on established weeds and kill green parts it contacts
3) systemic: sprayed on established weeds and are taken in by leaves and kill whole plant

Question 9

What are disadvantages of cover crops (3)?

Answer 9

• reduction in vine vigour (via competition) that can be excessive in poor soils/dry environments
• difficulty of mowing under-row area = time/labour
• unsuitable for steeply sloping vineyards (slippery when wet)

Question 10

3 regions that have experienced shortages in water supply in recent times:

Why?

Answer 10

Australia / California / S. Africa

Prolonged periods of dry weather.

Question 11

Drip irrigation is the ___ ___ type of irrigation used in vineyards.

Describe how it works (3):

Answer 11

• Most Common
  1) Pipes laid along each row (tied to lowest trellis wire)
  2) Drippers fitted at appropriate intervals
  3) Positioned away from vines to encourage root growth

Question 12

What are the 4 key components relating to soil health?

Answer 12

1. Soil structure: Good drainage, sufficient water-holding capacity, sufficient O, erosion resistance, root penetration ability.
2. Organic Matter / Humus: decomposing organic matter which supplies nutrients, improves soil structure+water-holding capacity.
3. Living Organisms: earthworms+microbes breakdown organic matter into humus/inorganic nutrients that are accessible to the vine.
4. Nutrients: Total amount of available nutrients needed for the vine to grow successfully.

Question 13

What are some steps a grape grower / winery can take to increase efficacy of water (7)?

Answer 13

• use of water-efficient irrigation systems (e.g. drip / RDI)
• use of drought-tolerant grapes (e.g. Grenache) + rootstocks
• reducing evaporation (e.g. mulch)
• reducing competition (e.g. removing weeds)
• increasing humus levels = better water retention (e.g. compost)
• re-using water for irrigation (e.g. after being used for cleaning)
• promoting depth of vine root growth (e.g. cultivation)

Question 14

What are the (3) advantages / (3) disadvantages of Regulated Deficit Irrigation?

Answer 14

AD: - vine growth/grape development are better controlled.

• less water needs to be used.
• especially advantageous for black grapes (reduced grape size = grater concentration of anthocyanins/tannins)

DIS: - timing of application/monitoring of water levels is crucial = need for skilled labor, special equipment.

• prolonged stress can lead to yield/quality reductions.
• even if successful, often results in lower yields, meaning improvements in quality must outweigh loss of quantity.

Question 15

What are (3) disadvantages of mulching?

Answer 15

• tends to be bulky = expensive to transport/spread.
• a lot is required to be effective.
• can increase vigor too much because of lack of competition.

Question 16

What is mulching?

Answer 16

The spreading of matter onto the vineyard soil to suppress growth of weeds (usually biodegradable materials e.g. straw/bark chips)

Question 17

Why is water quality an important consideration for vineyard irrigation (2)?

Answer 17

• Water high in dissolved solids (mud) = blocked sprinklers = needs filtering.
• Water high in salinity = difficulty for roots to take up water, vine dehydration = green parts will wilt/die.

Question 18

What are advantages of animal grazing as a method of weed control (3)?

Answer 18

• no chemicals (suitable for organic/biodynamic)
• they provide vineyard with manure
• they’re a source of meat for humans

Question 19

What is Regulated Deficit Irrigation?

When is it usually scheduled / why?

What type of irrigation system is used?

Answer 19

• a system of timing and regulating the amount of irrigation so the vine is put under mild-moderate water stress for a specific time within a growing season
• usually scheduled between fruit set and véraison to limit further shoot growth/encourage grape development.
• drip system used

Question 20

What is channel irrigation?

Answer 20

Similar to flood, but water flows down furrows dug between vine rows (more efficient)

Question 21

What is the most common type of contact herbicide used by grape growers?

Where has usage of this posed a problem?

Answer 21

• Glyphosate.
• High usage in S. Africa has led to glyphosate-resistant ryegrass.

Question 22

What are advantages of mulching (3)?

Answer 22

• doesn’t use chemicals (can be used for organic/biodynamic)
• can reduce water evaporation from soil (good in dry climates)
• can be a source of humus/nutrients

Question 23

What are advantages of drip irrigation (4)?

Answer 23

• economic use of water.
• possible to control water supply to individual rows / blocks
• can be used to apply fertilizer (“fertigation”)
• can be used on slopes

Question 24

How are overhead sprinklers used for irrigation?

What are PROS (2) / CONS (2)?

Answer 24

Overhead sprinklers are installed above the vines, water is pumped into them and then showered over the vines.

PRO: can be used as a method of frost protection.

• more targeted approach than flood irrigation.

CONS: expensive to install/maintain due to high pressures needed.

• uses a relatively large amount of water vs drip irrigation.

Question 25

What are 3 methods that can be used during growing season to increase the level of nutrients available for vines?

Answer 25

1) direct application of nutrients (e.g. fertilizers etc…)
2) promotion of biological activity and soil structure
3) management of weeds that can compete with vine (e.g. herbicides)

Question 26

What are organic fertilizers?

Answer 26

Fertilizers derived from fresh/composted plant/animal material e.g. manure or slurry.

Question 27

What is dry farming?

Why would a grape grower choose this method?

Answer 27

Farming practice whereby irrigation is not used, specifically in areas with limited rainfall e.g. Swartland, S. Africa.

Leads to lower yields + potential improvement in grape quality.

Question 28

What are some considerations that should be made when selecting cover crops for a vineyard (2)?

What is an example of a tool that assists grape growers in this process?

Answer 28

• Cover crops that are quick to establish and adapted to the soil/climate of the given region are best, and must be matched to the needs of the vineyard.
• Natural vegetation can be allowed to grow in vineyard, but cover crops allow more control from grape grower.
  e. g. Wine Australia has an online cover crop finder for specific conditions for grape growers.

Question 29

What are (3) advantages/ (2) disadvantages of mineral fertilizers?

Answer 29

AD:- can be tailored more to specific needs of soil.

• nutrients are already in inorganic form = more readily available to vines.
• More concentrated = cheaper to transport + distribute.

DIS:- no benefit for soil organisms/don’t improve soil structure

• more expensive.

Question 30

What conditions are more/less favorable for the use of RDI (2)?

Answer 30

• easiest in regions w/dry growing season and sandy/loam soils that dry out and can be re-wetted quickly.
• regions w/heavy or frequent rainfall throughout the growing season or w/heavy clay soils make RDI more difficult to be effective.

Question 31

What are advantages of herbicides (3)?

Answer 31

• cheap (labor/machinery)
• highly effective
• less damaging to soil than cultivation

Question 32

3 ways in which water can be regulated in areas with high rainfall:

Answer 32

• Building artificial drainage systems.
• Leaving natural vegetation to provide comepetition for water.
• Improve soil structure + remove plough pan to increase water drainage.

Question 33

What are cover crops (1) and what is their purpose (6)?

Answer 33

Plants (usually legumes e.g. beans, clover / cereals e.g. ryegrass, oats) that are specifically planted/allowed to grow to benefit the vineyard by:

• suppressing weeds
• improving soil structure
• competing with vine for water/nutrients (reducing vigor)
• managing soil erosion
• enhancing biodiversity
• provide a surface to drive on

Question 34

What are disadvantages of animal grazing as a method of weed control (3)?

Answer 34

• vines must be trained high (animals will eat grapes/leaves)
• animals need caring for = labor/cost
• animals are susceptible to vineyard pesticides

Question 35

What is cultivation (as a method of weed control)?

Answer 35

Method of weed control that involves ploughing soil to cut/disturb weed’s root systems.

Question 36

What is flood irrigation?

Where is this method common?

What are some PROS (1) / CONS (3)?

Answer 36

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

Commonly found in Argentina (using abundant water from the Andes)

PROS: Cheap/easy to install and maintain.

CONS: Inefficient (little water is actually taken up by the vine.)

Only usable on flat or v. gently sloping land.

Not suitable where water supplies are limited.

Question 37

What are disadvantages of herbicides (4)?

Answer 37

• risks of poisoning operator/consumer/environment
• weeds can become resistant with routine usage
• can increase vine vigour too much
• not allowed in organic/biodynamic