1. Taxonomy and Origin
2. Economic importance and Geographical distribution
3. Morphology
4. Edaphoclimatic Requirements
4.1. Climate
4.2. Light
4.3. Soil
5. Vegetal material
6. Growing techniques
6.1. Preparation of the land
6.2. Transplant
6.3. Direct sowing
6.4. Weeds
6.5. Density of plantation
6.6. Cutting
6.7. Manure
6.8. Watering
7. Pests and Illnesses
7.1. Pests
7.2. Illnesses
8. Physiopathology
9. Harvesting
10. Postharvest
11. Nutritional values


6.7. Manure

It has been proved that the asparagus is a crop with few nutritional requirements. Therefore, the quantity of the substances to be added will not be high. However, the elements should be added in the correct moments, when the plant requires them most.

Annual production of green asparagus per hectare (kg/ha)
Turions (t/ha)	N	P2O5	K2O	CaO	MgO
6.47	154.4	43.1	192.8	122.4	12.8
4.53	102.9	49.8	122.8	86.2	8
2.25	72	36	90	-	-

- Nitrogen: it influences the development and production processes, although excessive doses can lead to low performance, as the number and diameter of the turions are reduced.

The best moment for adding nitrogen is when the plants have already developed the feathery foliage.

Nitrogenous fertilization reduces the attacks of Rhizoctonia violacea as it favours the development of the mycelium so as to prevent the formation and spread of sclerotium.

- Phosphorous: Studies have shown that phosphorous reduces the fibrousness of turions, thus improving their quality. Moreover, the development of secondary roots is influenced by its presence or absence.

- Potassium: this is the element the plant makes most use of and its deficiency leads to a poorer quality of the turions.

- Calcium: the addition of calcium is important for this crop, due to the relationship of Ca and P, which should be at a ratio of 3/1.

- Magnesium: the performance of the crop depends on the relationship of K and Mg.

- Boron: it is the most important trace element, as the lack of it can lead to chlorosis in the cladodes and their subsequent desiccation and fall. It is also recommended to add basic manure to satisfy the needs of boron during the first phase of the growth. The level of boron should always be controlled, as it can be affected by a period of drought.

20-40kg of borax/ha should be added every three years.

* Due to the influence of microelements (magnesium and boron) in the behaviour of the asparagus growing, it is necessary to know the amounts contained in the plant as it is shown in the following table:

Amount of microelements in green asparagus (ppm)
Vegetative part	Iron	Copper	Magnesium	Boron	Zinc	Molybdenum
Turion	70	23	37	20	82	1.2
Stem	36	14	21	750	23	1.5
Cladodes	119	13	74		26	6.2

- Basic manure: it should be added during a deep ploughing in the first year:
30-60t/ha of manure.
60UF/ha of N.
100-200UF/ha of P₂O₅.
150-250UF/ha of K₂O.

- Late manure:

During the harvest, it is not convenient to add minerals, as they can unbalance the physiological process of the plant and, therefore, reduce the quality of the turions. We must remember that the plant is naturally prepared, due to the reserves accumulated during the vegetative development period of the previous year.

The addition of late manure is essential during the vegetative development. No mineral manures will be added after September, so as not to favour late sprouting.

During the second year, the following should be added:
15t/ha of manure.
70-90UF/ha of P₂O₅.
100-190UF/ha of K₂O.

From the third year onwards, the following elements should be added:
15t/ha of manure.
100-250UF of nitrogen.
70-100UF of P₂O₅.
150-250UF of K₂O.

6.8. Watering

Throughout the growing of green asparagus, there are three important moments related to its watering: the first one occurs during the plantation process and it only happens once in the first year; the other two relate to the harvest and the annual development of the over-ground part (these two are annual and variable according to the state of the crop).

The objective of watering the plantation is to keep the humidity of the radicular system and to help in the formation of the crown. Excessive water leads to chlorosis in young plants, causing the yellowing of the tips of the feathery heads; if, on the other hand, there is a lack of water, the feathery heads do not develop properly and the plant will be stunted.

The aim of watering the harvest is to maintain the humidity of the zone where turions will emerge and the surrounding areas. It should be taken into account that any alteration in the terminal meristem of the turion causes irregular growth, deformations and loss of over-ground tropism.

At the beginning of this period, the field should be watered to its maximum capacity, providing around 200-300 m³/ha; during harvest, 30-40 m³/ha should be applied weekly, depending on the soil, the growing technique, the climate, etc.

In general, those waterings should not be abundant, so that no puddle should form on the soil.

Watering the over-ground part influences the nutrients and the development of said part.

During this period, if there is no possibility of using drip irrigation, it is preferable to use gravity irrigation, instead of sprinkle irrigation, as this last system may favour the development of fungi illnesses that affect the over-ground part, especially rust.

The field should be watered once or twice a week; during this period, water needs may vary between 900 and 1000 m³/ha.

The field should last be watered in September, so as prevent late sprouting, which will use the leaf buds of the next harvest and will consume reserves of the roots; this new shoots will not have time to restore said reserves before the end of their cycle.

If there is local irrigation available, this system should be used throughout the cycle, not only during the harvest but also during the vegetative development. It is advisable to install two lines of drippers, one for each side of each line of plants. This is the best system of irrigation.

If this system is not available, sprinkle irrigation should be used during the harvest; microsprinklers are the best option. On the other hand, the traditional system of gravity irrigation should be used during vegetative development.

7. PESTS AND ILLNESSES

7.1. Pests

- Wireworms (Agriotes lineatus)

Adult specimens are 1cm long, black beetles, whereas larvae are cylindrical, yellow and hard and can be up to 25mm long.

As larvae development takes up to four years, in an infected soil we can find larvae of different ages. They live at different depths, depending on the moment of the year, as they are highly sensitive to heat and dryness.

They eat or pierce the underground organs of the plant: roots, crowns, bud leaves and turions.

- White Grubs (Melolontha melolontha L.)

Adult specimens are beetles up to 3cm long. Their elytrons are brownish-grey red and they have longitudinal striations and feelers

Larvae are white and cylindrical and they have a thick head and strong jaws.

Egg lying occurs at the beginning of the summer and they are laid at a depth of 20cm.

Damage to plant is produced when larvae eat the roots, rhyzomes and bud leaves, thus destroying the underground part of the plant.

- Myriapoda (Scugiterella inmaculata Newport)

This pest can cause significant damage to the turions while they are underground. They bite the turions and if their attack is too strong, they can weaken the crowns.

Adult specimens are whitish and 7mm long. They live at different depths and move through the spaces of the soil. Their attacks are stronger in cool, humid springs, as these conditions enable them to live nearer the surface and as the growth of the turions is slower; therefore in this case, there are greater possibilities of causing severe damage.

The signs are small holes on the turions. If the attack is very strong, big striations appear on the surface of the turion.

Control

- Eliminate dry stems of the previous harvest, as they can be a safe refuge for this pest.

- Crioceris (Crioceris asparagi L., Crioceris duodecempunctata L.)

They are colourful coleopterans that hibernate when they are adults to appear on the crops in spring when the first feathery foliage appears and lay eggs on the stems of the asparagus. The number of cycles is two.

Both when they are adults and larvae, they eat the leaves and stems. They can cause a lot of damage in young asparagus plantation.

Control

- Check for the appearance of the first adults.
- Insecticides should be aimed at attacking adult specimens.

- Asparagus Fly (Platyparea poeciloptera Schr.)

It is a pest that only attacks the asparagus. Adult male specimens of this dipteran are 5-5.5mm long, whereas adult female specimens are 7-7.5mm long. Their thoraxes are greyish, with three longitudinal black lines; their heads are yellow and the abdomen is black and long. Their wings have a characteristic brown strip that zigzags longitudinally.

They hibernate when they are pupas to appear as adults at the beginning of the spring and lay the eggs on turions, in general on the base of a scale. Larvae create passages under the skin of the plant so as to descend to the crown; afterwards, they widen said passages. Stems wither and die; consequently, the plant weakens a lot.

- Bean Fly (Phorbia platura Meigen)

Larvae penetrate inside the turions carving passages, which makes turions bend noticeably. They normally attack the thickest turions, although they can also attack ramified stems after the harvest. These attacks may sometimes cause subsequent cryptogamic infections.

Control

- After planting the asparagus, it is advisable to prevent damage during the first year. Crowns should be planted after the flies lay the eggs at the beginning of the summer.

- Asparagus Aphid (Brachycorynella asparagi Mordv.)

It is a small, greyish green species, with a long body.

The first specimens are apterous y appear in small colonies at the end of the spring on the inferior branches. Afterwards, winged specimens develop; they infect neighbouring plants, attacking the highest branches and sprouts.

Stems and branches get shorter, cladodes become yellowish and in next year's first ramifications the internodes appear too short and ramified from the bottom.

Control

- It is advisable to use aphicide that would not attack natural parasites and predators of this pest.

- Asparagus Moth (Hypopta caestrum Hbn)

They are lepidopterons with one annual cycle. Adults lay eggs on the base of the stem; then the larvae eat the young sprouts of the crowns and roots, leaving just the skin. They spens winter as larvae in diapause and when spring comes, they surface as nymphs.

Control

- It is advisable to pick up the pupas.

8.2. Illnesses

- Rust (Puccinia asparagi DC)

It is the most common illness in asparagus plantations and it spreads quickly if it is not treated correctly. Infection may start during spring. In 1-year plantations, pycnidia (weak, sticky, elliptical, yellowish green spots) appear on the over-ground part. In adult plantations, this fungus does not appear; on the other hand, at the beginning of autumn, swellings directly appear in stems, which, 15-20 days later, open to give way to reddish-brownish grey pustules called uredosores, full of numerous spores that serve as the propagation mechanism of the fungus. When plants are under severe attack, the over-ground part dries up in a few days.

Damage to the crop are related to the limitation of the development of the plant’s vegetative organs, which during this growing phase synthesize reserves to accumulate them in the underground system of the plant, the rhyzome and the main roots and which will serve as the basis for the following year’s production.

- Control

It is almost impossible to eradicate this illness once it is present in the crop, so it is advisable to keep it to the possible lowest level.

- Plantation rows should run following the direction of the dominant winds of the area, so that the over-ground part has as little humidity as possible.
- Plantation frames should be as separated as possible to favour ventilation and wind circulation.
- The rests of the over-ground part should be burnt, as if they are buried, new sources of infection are incorporated to the soil.
- In case of lush asparagus plantations, great care must be taken at east until the beginning of autumn.
- Localized irrigation should be used instead of flood irrigation as this may turn water into a propagation vector of the illness.
- Resistant varieties should be planted.
- Preventive chemical treatments should be applied to interrupt the propagation cycle.

In young plantations, the treatments should be carried out in spring, whereas in adult plantations, they should be applied at the end of the harvest.

- Stemphylium (Stemphilium vesicarium Wallr)

This illness is characteristic of areas where humidity is localized.

The first symptom is the appearance of small, black pits on the dry scales located at the base of the main stems of the plant. These points turn into circular or oval, 2-6mm diameter spots, whose centres are greyish brown, edged by a violet halo.

Consequently, we can differentiate different phases: at first, it becomes chlorotic, then it turns dark brown and finally the cladodes of the feathery heads are lost, thus leaving the over-ground part of the plant bare naked.

This illness spreads through spores; its spread is favoured by morning mist, sprinkle irrigation, rivers, etc. All that is boosted by the use of cultivated varieties with great vegetative development, a high density of plantation, the overuse of nitrogenous manure that favours the development of the over-ground part of the plant, etc.

Damages lead to a reduction of the foliar surface and the subsequent reduction of photosynthetic activity, which influence the productive and qualitative performance of the following harvest.

Control

- Clean and eliminate affected plants.
- Control irrigation and drainage of the field so as to prevent the formation of puddles.
- Use a system of localized irrigation.

- Botrytis or Grey Mould (Botrytis cinerea Pers)

This illness, which mainly attacks the turion, produces soft rot that is subsequently covered by greyish felt produced by the mycelia; this will then become white and under its surface black, hard corpuscles (sclerotia) will appear.

If the feathery heads get infected, they will become first yellow and then grey.

The only damages are the lost of turions and the reduction of it photosynthetic capacity.

Control

- If the asparagus is grown in greenhouses, it is advisable to regulate the humidity of the soil and ensure the correct ventilation of the place.
- Chemical treatments should be applied during the harvest if the autumn was humid, taking into account the safety period.

- FUSARIOSIS (Fusarium culmorum Sacc)

This illness irreversibly affects the plant and its yield and may shorten the commercial life of the plant, especially after some years of production.

This fungus gets into the plant by the wounds caused by the working of the land, mechanical treatments, attacks of pests, natural causes, etc.

Symptoms usually appear in summer; at first, the feathery heads become chlorotic and then they turn silver, although they do not loose their cladodes. If we transversely cut them, we may see vascular oxidation and necrosis in the cortical area. As for the radicular system, the main roots show a total lack of reserves, leaving a hollow epidermis.

During the harvest, the turions may quickly fade and wither and their surface may be invaded by a layer of with or pink mycelia.

Control

- Avoid clay, semi-permeable soils.
- Disinfect the vegetal material.
- Unbalance in the relationship of calcium and magnesium that may favour infections.
- Eliminate the remains of the turions after the harvest.
- It is advisable to put fungicides in contact with the radicular system of the plant, which is best achieved by the use of localized irrigation.

- Rhizoctonia (Rhizoctonia violacea Tul)

This illness leads to the production of small turions with a tendency to branch out; subsequently, the plants start to dry up. The infection occurs in the rhyzome and the collar of the stem; its clearest symptom is the appearance of a pink layer that will then turn purple.

The infection of neighbouring plants occurs through mycelia that go from the infected plant by rhyzomes emitted from it to the healthy plant.

Control

- Avoid planting in contaminated soils or fields where carrot, beetroot, alfalfa, potato, etc used to be grown.
- Disinfect crowns.
- Isolate the area where the infected plant was and apply several active substances.

8. PHYSIOPATHOLOGY

- Withering of young sprouts: this happens when young sprouts are about to branch out. There may be several causes for this, including lack of boron, water deficiency, etc.

- Re-sprouting in autumn: if ambient conditions in autumn are favourable, new sprouts may develop, which is detrimental as it uses the reserves that serve as the sources for the sprouting of new turions the following year. This can be controlled avoiding late manure and irrigation.

9. HARVESTING

The moment for starting the harvest is determined by quality standards on the size and colour of the turion that should not have open bracts in its head.

Mechanized harvest is recommended for outdoors plantations, as turions are not covered by soil.

If asparagus is grown in greenhouses, harvest must be done manually. Tools used for cutting range from coutlers at an angle of 100º to sharp thin-bladed knifes.

During the first half of the harvest, turions should be cut at a length of 30-35cm, while in the second half, as temperature rises, turions should be cut at a length of 22-25cm.

When grown in greenhouses, the harvest is 15 days shorter than in the case of outdoors plantations.

10. POSTHARVEST

Once turions have been cut, they should be kept in vertical position until they are in their final package so as to prevent their apical tip from bending due to geotropism. Furthermore, their bottoms should be immersed in water.

For selling fresh asparagus, they should be tied in bunches with strings or elastic bands and/or placed in small, polythene bags for storage in boxes that can be piled up.

Cold storage should be at a temperature of 2-3ºC and at a relative humidity of 95-100%; it should be taken into account that the asparagus quickly looses its organoleptic properties.

11. NUTRITIONAL VALUES

Nutritional values of asparagus per 100g. of dry matter
Water (%)	93.75-94.5
Albumin (%)	1.62-1.79
Fat (%)	0.11-0.25
Sugar (%)	0.37
Non-nitrogenous extracts (%)	2.26-2.33
Fibre (%)	0.81-1.04
Ashes (%)	0.54-0.70
Calcium (mg)	20
Phosphorous (mg)	60
Iron (mg)	1
Vitamin B1 (mg)	25
Vitamin B2 (mg)	170
Vitamin C (mg)	30
Vitamin A (U.I.)	900
Energy (cal.)	26

Author: Infoagro