Managing Nutrients and Water Flashcards
Explain how to manage soil health?
Within grape growing, soil health is the ability of the soil to support the vine, enabling it to grow and produce fruit. It is related 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.
- 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.
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 – whether to improve the structure of the soil (for example by adding compost) or by adjusting nutrients.
Explain nutrient management?
The right balance of nitrogen, phosphorus and potassium as well as many other nutrients is essential for healthy vine growth and the ripening of grapes.
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. Some of these techniques involve direct application of nutrients (in either organic or inorganic form), some involve the promotion of biological activity and soil structure, and some involve the management of weeds (unwanted plants) that can compete with the vine for nutrients (and water). Many of these techniques have multiple functions, and can influence accessibility of water as well as nutrients.
The removal of weeds is usually desirable for additional reasons. 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. Some weeds also hamper the passage of machinery and personnel (e.g. stinging nettles, brambles).
Explain organic fertilizers?
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).
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. 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.
Explain inorganic fertilizers?
Inorganic fertilizers, also called synthetic fertilizers, are manufactured from minerals extracted from the ground or synthetic chemicals.
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.
Explain cultivation, it’s advantages and disadvantes?
Cultivation is a method of weed control that involves ploughing the soil to cut or disturb the weeds’ root systems.
Advantages include:
- 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.
Disadvantages include:
- 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)).
Explain herbicides, it’s advantages and disadvantes?
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.
Advantages include:
- 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.
Disadvantages include:
- 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.
Explain animal grazing, it’s advantages and disadvantes?
Another method of weed control is to allow animals, such as sheep, to graze in the vineyard.
Advantages include:
- 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.
Disadvantages include:
- 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, it’s advantages and disadvantes?
Cover crops are plants that are specifically planted, or allowed to grow, that have a beneficial effect on the vineyard. 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. 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 widely used around the world, but have to be matched to the needs of the vineyard. For example, Wine Australia provides an online cover crop finder for particular conditions for its grape growers.
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).
Advantages include:
- 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.
Disadvantages include:
- 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.
Explain mulching, its advantages and disadvantes?
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.
Advantages include:
- 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.
Disadvantages include:
- 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).
Explain irrigation?
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.
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.
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.
Explain sources of water and efficiency of us?
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.
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. Steps taken in the vineyard include:
- 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 – see Nutrient Management)
- 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).
Water is also a valuable resource in the winery, where it is mainly used for cleaning. Consideration of ways in which this water can be re-used (e.g. some may be suitable for irrigation) can also maximise efficiency of water consumption.
Explain the importance of water quality?
Assessing the water quality is also important. Water that is high in dissolved solids such as mud can block sprinkler and drip irrigation systems and therefore needs settling and filtering before use.
Water that contains high levels of salt (high salinity) can also be problematic, as is the case in many areas in Australia. 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.
Explain irrigation and its advantages and disadvantages?
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.) The key benefits of these systems are that:
- 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.
The disadvantages are that:
- installation costs are relatively high, but maintenance costs are moderate
- clean water is required, otherwise the drippers quickly become blocked
- however, 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.
Explain flood irrigation?
In flood irrigation, water is stored behind a sluice and at the scheduled time released to flood the vineyard. 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.
Explain channel irrigation?
Channel irrigation is similar; however, the water flows down furrows dug between the vine rows, which can help increase efficiency of water use. These systems are common in Argentina because of abundant water from the Andes. They are not suitable where water supply is limited.
