The onion

The onion

The onion (Allium cepa L) is a biennial plant of the family Alliaceae. It is native to Southeast Asia. The consumed part is the bulb. Culture is one of Morocco's main vegetable crops with an area ranging from 18,000 to 20,000 ha. The total production of onion bulbs is 300,000 to 400,000 tons / year or an average of 18 to 21 T / Ha. Tadla holds across the country in second place (11-12% of acreage) after the region of Meknes (16-21%). Indeed this garlicky is conducted generally at the summer crop area (83% of onion acreage).
The nutritional value of vegetables is high (Protein 1.4%, Fat 0.2%, Carbohydrates 10% Carbohydrates 4-18% Energy 40-49 calories / 100 g FW, Vitamins B1, B2 and C. Medicinal uses of onions are numerous: it is an appetitive and facilitating digestion, an energy food and support, an anti-diabetic, antiseptic and vermifuge, tonic factor (vasodilation of blood arteries), diuretic, aphrodisiac and anti -rhumatismal powerful.
Soil and climatic requirements of the crop:
Bulbing began when the photoperiod exceeds a critical threshold (depending on variety): 10-13 hours / day for cultivars short day and 14 hours / day for long day varieties. The rise in seed "bolting", corresponding to the issue of the scape, is generally medium size bulb on exceeding 20-25 mm at relatively low temperatures (below 10 ° C). A bulb juvenile phase (diameter <17 mm) can ride a flower even in very cold temperatures. Varieties "long day" respond relatively quickly to bolting under cold (4-10 ° C), compared to cultivars "short day". The bulb goes dormant at cold temperatures (- 1 to 4 ° C) or high (> 20 ° C). A high relative humidity of the air (> 70%) favors rooting and harvested bulb and reduces its quality. The optimum germination takes place at an air temperature between 23 ° and 27 ° C (initiation process between 2 and 3 ° C). The optimum growth between 20 and 24 ° C air (minimum 8 ° C, maximum 30 ° C) and between 10 to 30 ° C the ground. Culture resistant to cold up (-5) to (-10) ° C for the foliage and the threshold (-15) ° C for the bulb. Vernalization or dormancy, followed by bolting, is caused by low temperatures (4-10 ° C) for a long period (4-8 weeks). The plant is demanding to light especially at the "seedling". Bulbing normally requires a minimum of 10 hours of light per day (varietal character). An excessive air humidity (> 70% RH) can cause a resurgence of deadly fungal diseases (mildew). Germination is less demanding in that the water growth; Indeed 75% of the seeds can emerge in a very dry environment (soil moisture near the yield point). The optimum is in the vicinity of the capacity of the field soil. Culture is not demanding in soils, with the exception of a poor clay texture humus (constraints adhesiveness and plasticity clays), while the sandy loam soil well fertilized promote earliness in addition to improving productivity. The suitable pH is close to neutral (6.5 to 7.8). The maximum tolerable salinity is 1.2 mmhos / cm.
Varieties, sowing, planting and soil work:
The varieties are known in Morocco Doukkala red, red and yellow Amposta Valencia. Be careful in the selection of varieties (avoid importing varieties of long days that require more than 15-16 hours to their bulbing; this day duration is not common in Morocco, but should be choose varieties day Short whose critical photoperiod is low.
The germination of seeds is easily lost if the packaging of the seeds is not airtight. We should buy the seed of a known house, with packaging own home and variety. Sowing is in the nursery. The seed rate is 12.5 g / m². This is followed by the preparation of seed beds. It covers these boards manufactured by the substrate.
The stand is adopted 200-250 thousand plants / ha. After two to three months in the nursery, seedlings are carefully plucked (after copious wetting the ground) and are transported on the plot for planting. This parcel should be well prepared (plowed, leveled, rolled and billonnée). Planting is done arrangements 60 cm x 3 cm. Can make cuvettes 4 or 5 lines, spaced 30 cm. It also leaves the passages between 50- 60 cm cuvettes. The soil working should be deep to facilitate magnification bulbs. Lines must be spaced apart enough to be able to hilling. Ridging thus preferred to the bowl.
Irrigation:
In general culture demands a good distribution of water supply: (1) early varieties require a total water volume of about 400 mm / production cycle. (2) late varieties in need of approximately 600 mm / cycle. It is necessary, in all 10 irrigations a unit dose of 7 to 13 mm / day. Irrigation can be controlled by the tray class A; we take as cultural 0.5-0.8 coefficient during the period transplant - bulb beginning magnification; 1 bulb for the grow-out period and stopped irrigation during the period close to maturity harvest.
Fertilization:
The base formula is 80-150-150 kg / ha, respectively of N, P2O5 and K2O. The overall formula is 250-150-350 kg / ha N respectively, P2O5 and K2O. The difference being the top dressing. Nitrogen can be added in the form of ammonium nitrate, as supertriple P and K in the form of potassium sulphate. We recommend the manual location of fertilizer in the middle of the line. Can be up to 4 splits N and K (nitrogen 50unités for planting units 50 20 days after recovery 40 units of nitrogen with 100 units of potash just at the beginning of bulb magnification, 30 units nitrogen potash with 100 units during the bulb grow. The sulfur intake is important for the conservation of onion. The S element helps the good conservation of the bulbs.
  Pest control:
The main enemies of culture are thrips, leaf miners, cutworms and white, mildew, nematodes, physiological disorders (hollow bulb apical browning). Treated with different active substances according to the anomaly. Mancozeb is used often, the hymexazol the Ripost (Oxadixyl + mancozeb + Cymoxanil), the Maneb, Benomyl, Methyl parathion, pirimicarb, Dicofol and 44 PELT (MA Methylthiophanate). These treatments can be preventive (best) or curative (in cases of infestation).
Harvest and storage:
  Before harvest of conservation onion (large colored bulbs), we apply a weed killer and an inhibitor of germination and growth on foliage to cause leaf senescence. Irrigation was stopped a month before the uprooting of plants and proceeded to soak the bulbs by exposing the plants uprooted in the sun for one to two months (we let the plants uprooted from their place along the ridge). We must take care of these bulbs turning. In order to condition the bulbs mounds, they must be left carrying their leaves. The best storage conditions are (1) 0 ° C and 95% RH or (2) over 30 ° C and dry atmosphere (never between 7 and 28 ° C, with high relative humidity).

Agronomic and Veterinary Institute Hassan II