Managing Nutrients and Water Flashcards
What does managing soil health refer to?
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 (see Soil Preparation).
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 (see Nutrients).
What are organic fertilisers?
Organic fertilisers are derived from fresh or composted plant or animal material, such as manure or slurry. Cover crops can be grown and mown into the soil to decompose and provide nutrients (termed green manure). Some O.F 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. However, 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. This also means that the nutrients become available to the vine gradually, which can be an advantage. However, a disadvantage is that they can be bulky and therefore expensive to transport and spread.
What are mineral fertilisers?
Mineral fertilisers are extracted from the ground or chemically manufactured. 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. They hold no benefit for soil organisms and do not improve soil structure. They are often more expensive than organic fertilisers to purchase, but, as they are more concentrated, much cheaper to transport and distribute.
What is meant by cultivation?
Cultivation is a method of weed control that involves ploughing the soil to cut or disturb the weeds’ root systems.
What are the advantages of cultivation?
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.
What are the disadvantages of cultivation?
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)).
What are herbicides and what are the three types?
Herbicides are chemical sprays that kill weeds. There are three types of herbicides:
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.
Contact herbicides are sprayed on established weeds and kill the green parts of the weed that they contact.
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.
What are the advantages of herbicides?
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.
What are the disadvantages of herbicides?
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.
What are the advantages of animal grazing?
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.
What are the disadvantages of animal grazing?
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.
Explain cover crops and their use in managing soil nutrients.
Cover crops are plants that are specifically planted, or allowed to grow, that have a beneficial effect on the vineyard. May be grown to suppress weeds. 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. Cover crops that are quick to establish and are adapted to the soil and climatic conditions are best. Examples of cover crops include legumes (such as beans and clover) and various cereals (such as ryegrass and oats). Cover crops are used around the world, they have to be matched to the needs of the vineyard.
It is also possible to leave natural vegetation to grow in the vineyard to achieve any of the above aims. Although this is cheap, and can permit greater diversity, specific cover crops with known characteristics allow more control.
The cover crop must be managed so that it does not compete too much with the vine for water and nutrients at key times in the vine cycle. If ploughed into the soil, the cover crop or natural vegetation can provide organic matter and, in this way, fertilise the soil (this is called green manure).
What are the advantages of cover crops?
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.
What are the disadvantages of cover crops?
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.
What is mulching?
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.
