Onion

The bulb group consists of a wide range of under ground vegetables like onion, garlic, leek, chives and shallot etc.

Onion and garlic are the most important among these, being grown in Himachal Pradesh on commercial scale especially garlic.

OnionBotanical Name: Allium cepa L. Family: Amaryllidaceae Chromosome number 2n=16Origin : Central and South Western Asia

♥ Onion is the most popular and widely grown vegetables in low and mid hills during winter season.

♥ The onions cultivated in high hills (May-October) and kharif onion in low hills can be a more profitable venture.

♥ Pungency in onion is due to an enzymatic reaction only when tissues are damaged.

♥ It is due to the presence of sulphur bearing compound in very small quantity in the volatile oil of the plant juice. The major compound is allyl-propyl-disulphide.

♥ Colour: There are 4 classes – White Yellow Red and Brown.♥ Red colour is due to anthocyanin pigment and yellow is due

to quercetin pigment.

♥ The green leaves and immature and mature bulbs are eaten raw ♥ Used in preparation of sauces, soups and seasoning of food on accounts of its

special characteristic pungency.♥ Also used in processed form e.g. flakes, powder and pickles.♥ Onions are diuretic, applied on bruises, boils and wounds.♥ Relieves heat sensation.♥ Bulb juice is used as smelling on hysterical fits in faintness.♥ Used to relive insect bites and sour throat.♥ Results of investigation suggested that onions in the diet may play a part in

preventing heart diseases and other ailments.♥ Onions are given in jaundice, spleen enlargement & dyspeptic after cooping

in vinegar.♥ In malarial fever, they are eaten twice a day.♥ Roasted onion mixed with cumin, sugar candy and butter oil are a

demulcent of great benefit in piles.♥ The essential oil contains a heart stimulant, increases pulse volume and

frequency of systolic pressure and coronary flow and stimulates the intestinal smooth musculature and the uterus.

♥ Reduces blood sugar & has lipid lowering effect.

Importance and Uses

♠ Soil should be friable, fertile, well drained and have an abundant supply of humus.

♠ A heavy soil is not desirable that bakes and crusts after irrigation.

♠ Sandy loam and silt loams are best suited to it.

♠ The soil pH should be in the range of 5.8-6.5.

♠ It is sensitive to high acidity and alkalinity.

Soils

Climate♣ It grows in mild climate without extremes of high and low

temperature♣ Plants at early stage can withstand the freezing temperature.♣ Optimum temperature for seed germination should be 20-25oC.♣ Low temperature and short photoperiods are required for

vegetative growth. ♣ Relatively high temperature and long photoperiods are needed for

bulb development.♣ It requires 13-21oC for vegetative growth before bulbing and 16-

25oC for bulb development and 25-30 oC for bulb maturation.♣ Low temperature (<15 oC) for long period in bulb crop favours

bolting which is not desirable.♣ Low temperature of about 10-15oC is required for seed stalk

initiation ♣ Under high temperature (18-20oC) plants do not bolt either in

short day or long day.♣ Long day varieties do not bulb under short day whereas short day

varieties if planted under long day will develop bulbs.

Photoperiod► Onion is normally regarded as long day plant i.e. bulb formation is promoted

by long day conditions.► The cultivars differ greatly in day length requirement.► Photoperiod requirement in onion is a quantitative character and each cultivar

needs a minimum day length for bulb formation which is known as critical value.

► This critical value in combination with temperature influences bulb initiation.► The so called short day cultivars when passed the critical value limit will

initiate bulb formation and development is continued under long day conditions.

► Conversely, a long day cultivar will not be able to initiate bulb formation unless its longer critical value of photoperiod is reached.

► If onion plants are kept under short day conditions they continue to grow for over 3 years without bulbing.

Conclusion:► High percentage of non-bulbous plants if a particular cultivar is exposed to day

length photoperiods less than necessary for bulbing.► Conversely bulb prematurety occurs when cultivar is exposed to day lengths

longer than the required for bulbing resulting in reduced bulb size and low yields.

► Therefore, care must be taken in choosing appropriate cultivar.

Onion cultivarsCommon Big Onion (rabi)

Red Coloured

Agrifound Dark Red, Agrifound Light Red, Arka Niketan, Arka Pragati, Hisar-II, Kalyanpur Red Round, N-2-4-1, Punjab Red Round, Punjab Selection, Pusa Madhavi (Good Storage), Pusa Ratnar (Fair in storage), Pusa Red, Udaipur 101, Udaipur 103, VL-3

Kharif Onion

Arka Kalyan, Arka Pragati, Baswant-780, N=53, Arka Niketan (can also be grown in late kharif in Mar

White skinned varieties

Pusa White Flut, Pusa White Round, N-257-9-1, Punjab-48, Udaipur-102

Yellow skinned varieties

Brown Spanish (Long day variety, suitable for growing in hills), Early Grano (Good for salad, suitable for green onions)

Multiplier Onion

Agrifound Red, CO-1, C-2 (resistant to purple blotch), CO-3 (resistant to thrips), CO-4 (moderately resistant to thrips), MDU-1

Small Onion

Agrifound Rose (pickling type, suitable for export), Arka Bindu

Cultivars suitable for growing in Himachal Pradesh

Patna Red

N-53

Agrifound Dark red

Brown Spanish

DPO-1

DPO-1 (a variety in pipe line)

Patna Red

Planting Time (India)Season Time of sowing Time of transplanting Harvesting

time

Northern IndiaRainy(Kharif ) May- June (July) July- Aug (Mid Aug) Nov-Dec

Winter (rabi) Oct-Nov (Nov) Dec-Jan (Jan-early Feb)

May-June

Maharashtra and Parts of GujratRainy (kharif) May-June July Aug Oct-Dec

Late rainy (kharif) or early winter (rabi)

Aug-Sept Sept-Oct Jan-March

Winter (rabi) Nov-Dec Dec-Jan April-June

Tamilnadu, Karnataka & A.P.Early rainy (kharif) April-May May-June August

Rainy (kharif) May-June July-Aug Oct-Nov

Winter (rabi) Sept-Oct) Nov-Dec March-April

Nursery Sowing and Transplanting Time

►Seedlings become ready for transplanting in 8-10 weeks time.

►Seedlings must be about 15-20cm in length at the time of transplanting.

Region Nursery Sowing Transplanting Time

Low Hills 1. Mid November (Poly-house)2. June- July (Kharif onion)

1.December- January 2. July -August

Mid Hills

Mid October – Mid November December

High Hills April May - June

Seed Rate

Spacing

8-10 kg/ha

►15 cm between rows and 5-8 cm between plants to plant ►Transplanting on ridges is ideal for kharif onion crop.►Partial prunning of top is done in over-aged tall seedlings to

augment the stand of the crop. It also provides convenience in planting.

Sets ☻These are small dry onion bulbs produced in the previous year.☻These mature 3-4 weeks earlier and tend to yield higher than

the seeded onions.☻Commercially used to produce early green onions but also used

for dry bulb production.

Soil preparation and transplanting

♣Onion should be planted in well pulverized field.

♣Plough first with soil turning plough followed by 4 to 5 ploughings with country plough.

♣Then carry out leveling. ♣Onion is normally planted in flat beds however

kharif onion is planted on ridges. ♣Transplanting should be done during late

afternoon.

Manures and Fertilizers

FYM (q/ha) N P2O5 K2 O

(Kg/ha)

250 120 75 60

☻Full dose of farmyard manure and phosphorus, potassium and one-half of N should be applied at the time of transplanting.

☻Remaining part of N should be top dressed in two equal halves at an interval of one month each.

☻Application of S is found to improve quality and pungency when applied @ 20 kg CaSO4/ha.

Open pollinated varieties

►Onion is a closely planted and a shallow rooted crop.►Hand weeding is difficult which may damage the crop. ►Use of chemical weedicide along with one hand weeding at

critical growth stage is beneficial. ►The critical period of crop-weed competition is between 4-8

weeks. ►Application of Alachlor (Lasso) @ 2 litres/ha or

Pendimethalin (Stomp) @ 3 litres/ha in 750 liters of water before transplanting is beneficial for controlling weeds.

►3 weedings are sufficient to harvest economic crop if performed 30, 50 and 75 days after transplanting.

Weed control

Irrigation

╠ Onion needs very careful and frequent irrigation as it is a shallow rooted crop.

╠ Water requirement of the crop at the initial growth period is less and increases during later growth stages.

╠ Irrigation is to be applied at an interval of 10-15 days in cool weather and at a week interval during hot weather.

╠ Bulb formation and bulb enlargement stages (60-100 days after transplanting) are the critical for water requirement.

╠ Insufficient moisture tends to slow down bulb growth while over supply causes rotting.

╠ A dry spell may cause splitting of the outer scales. ╠ Generally, 10-12 irrigations are given in rabi season. ╠ Stop irrigation when the tops mature and start falling down.

Growing kharif onions by sets Onion sets are small bulbs ( around 0.25-1.0 inch in diameter) grown in

the previous year. These sets are used as the propagating material for the production of

dry bulbs and bunching onions. Variety recommended for this crop is N-53. 5-7.5 kg seed is enough to raise sufficient number of sets to plant one

hectare area. Sowing of seed is done during end of January or beginning of February

(left plants at same place till April). In April, plants form small sets due to close spacing. The plants are

uprooted and tops are removed. The sets having 1.5-2.0 cm in diameter and disease free are selected

and stored till July. About 10q sets are enough to plant one hectare area. Sets are planted at 10cm apart in rows on both sides of ridges spaced

35-45 cm. Sets are normally planted by July-August to get an early crop by early

November.

UNUSAUAL ONIONS

Some very different types of onions are available:

Multiplier Onion or potato onion (A. cepa, Aggregatum group): sends up multiple tops, each of which produces small onion bulbs in clumps.

Egyption onion or tree onion (A. cepa, Proliferum group): produces bulblets at the tops of the stalks instread of flowering.

Pickling onions or pearl onions: produces small bulbs which are pickled & used as condiments.

Harvesting☻Onions are ready for dry bulbs harvesting when the tops get dried

(or neck fall stage) and bulbs are mature. ☻Harvesting at this stage results in higher yield, longer storage life of

bulbs and less neck rot. ☻The green onions can be harvested from the time they reach pencil

size up until bulbing begins. ☻To hasten the maturity process, the tops can be rolled down with a

light weight roller when about 10% of the tops have fallen naturally. ☻Late harvesting results in thick necked bulb, sunken and also poor

storage life.☻Desirable to leave 1.5-2.0 cm of the tops attached to the bulb as it

helps to close neck and reduce storage loss.

Yield (q/ha) Rabi crop 250-300q/ha

Kharif crop 200-250q/ha

Curing

☻Curing or drying of bulbs is an important process to remove the excess moisture from the outer skin and neck of onion.

☻This helps in reducing the infection of diseases minimizes shrinkage due to removal of moisture

from the interiors. ☻An additional measure for the development of skin

colour.☻Practiced to remove field heat before storage of

onion bulbs.

Cont……

Curing cont……

◙ Bulbs are either cured in field or in open shades or by artificial means before or in storage.

◙ Onions are considered cured when neck is tight and the outer scales are dried until they rustle.

◙ Thorough curing is essential for 2-3 weeks (kharif crop) along-with tops when the temperatures are low during winters.

◙ In winter crop, bulbs are cured in field for 3-5 days in wind row method and cured in shade for 7-10 days to remove field heat.

◙ Bulbs are artificially cured by passing hot air at 46 oC for 16 hours when temperature is low.

◙ Shade curing improves bulb colour and reduces losses during storage.

Storage◙ Onion bulbs have a rest period for about 2 months.

◙ Proper storage is important as higher temperature induces sprouting.

◙ Essentials for successful storage are

Thorough ventilation, uniform comparatively low temperature, low humidity, proper maturity, optimum application of fertilizer, freedom from disease infection

◙ Bulbs are stored in special houses with thatched roof and sides covered by bamboo sticks with provision for good air circulation.

◙ Periodical turning is necessary.

◙ Losses in the range of 25-60 %.

◙ Cold storage at 4-6 oC and 65% RH.

◙ RH is lower than the most vegetables because dampness in storage cause considerable rot and mold growth.

PHYSIOLOGICAL DISORDERS

Possible Reasons

1. Bolting ☻ It means emergence of seed stalk prior to time of bulb formation and

adversely affects the formation and development of bulbs.

♣ Transplanting of aged seedlings♣ Early sowing of seeds in the nursery beds which results in

the formation of small sets.♣ Late transplanting of seedlings♣ Restricted or poor vegetative growth also leads to bolting.♣ Sharp fluctuations in temperatures at bulb initiation

stage.♣ Low temperature (10-12 oC).♣ Poor supply of nitrogen in nursery and field.

Management

►Time of planting should be adjusted in such a way that the crop may expose to moderate temperature at bulbing.

►Sowing of nursery at proper time►Transplant healthy and 6-7 weeks old seedlings.►Supply recommended dose of nitrogen.

2. Sprouting ☻An important disorder in storage of

onion and garlic and results in huge losses.

☻ It is associated with excessive moisture at maturity and supply of nitrogen.

Management

◙ Adjust time of planting in such a way that harvesting can be done in dry period

◙ Stop irrigation as soon as bulbs reach maturity

◙ Spray Maleic hydrazide 2000-2500 ppm or iron sulphate or borax @ 500-1000 ppm 2-3 weeks prior to harvesting.

Disease Management

Purple Blotch (Alternaria porri)☻ This disease occurs during favourable environmental conditions

(temperature 28-30 oC & RH 70-90%).☻ Higher incidence during kharif (62%) as against 38% in rabi.

► Small, sunken, whitish flecks with coloured centers occur on leaves and flower stalk. Further, large purple area develops forming dead patches.

► The intensity was observed from 5-25% on bulb crop & 10-45% on seed crop.

► Disease appears from mid Feb-April.► The leaves and stem fall down from point of attack.► Serious constraint in onion seed production in India.

♣ 3 summer ploughings reduce the disease severity.♣ Dithane-M-45 (0.25%) is effective.♣ Mancozeb @ 0.25% at 15 days interval is effective &

also cuprous oxide 75WP (0.25%) is effective.♣ Ecofriendly method: 2 sprays of palma rosa oil

(0.1%) first at the time of appearance and second 15 days later.

Management

Stemphylium Blight

☻ Appears on onion leaf as well as on leaf stalk.☻ Infection appears as small yellow to pale orange spots or streaks in the

middle of leaves/flower stalks on one side.

♣ Dithane-M-45 (0.25%) alongwith sticker triton can control the disease.

Management

Basal Rot

☻ Rotting of bulbs is caused by Fusarium fungus & bacteria. Basal rot caused by Fusarium oxyysporium f.sp. cepae is wide spread disease.

► The common symptoms are wilting & rapid dying of leaves from tips as the plants approach maturity & roots turn pinkish.

► Later on most of roots rot.► The bulbs become soft & ► On cutting, a semi watery decay is found

advancing from base of the scales upward.

♣ Satisfactory control can be achieved by flooding in non-growing season.

♣ Patna Red, N-257-7-1, Udaipur-103 are resistant.

Management

Downy Mildew (Peronospora destructor)☻ Caused in high humid location on the surface of leaves or flower stalk, violeet

growth of fungus is noticed which later become pale green yellow and finallu the leaves or seed stalk collapse.

☻ In storage, bulbs of infected plant become soft, shrivelled & outer scales become amber in colour.

► The common symptoms are wilting & rapid dying of leaves from tips as the plants approach maturity & roots turn pinkish.

► Lateron most of roots rot-off.► The bulbs become soft & when cut, a semi watery

decay is found advancing from base of the scales upward.

♣ Crop rotation with a 4 year break in onion cultivation.

♣ Good weed control and field hygine.♣ Removal of primary infected onion plants.♣ Spray of 0.2% Zineb.

Management

Onion Smut

☻ Soil borne disease.☻ It appears as elongated dark slightly thickned areas at the base of seedling.

The black lesions appear near the base of the scales on planting.☻ The affected leaves bend downward abnormally.

♣ Seed treatment with 55-85 g of arsan per 4.5 kg of seed before sowing.

♣ Treatment of soil with thiram alongwith methocal sticker.

Management

Insect-Pests

Thrips☻ Thrips tabaci is the major injurious pest of onion & garlic.

► Onion infested with thrips develop spotted appearance on the leaves which turn into pale white blotches due to drainage of sap.

► The adults hibernate in soil on grass and other plants in the onion field.► The thrips also over winter in bulbs and act as a source of infection in the

following year.► Thrips multiply in large number during March and April both on seed and

bulb crop in North India whereas in Nasik area, thrips incidence was even observed in the Jan & Feb.

♣ ♣ Application of carbosulfan (0.1%)/

malathion(0.05%) or fenitrothion(0.05%) has proved effective.

♣ Among synthetic pyrethroids, cypermethrin @ 0.0075% has also been found effective.

Management

Head Borer☻ The larva cuts the pedical of flower and feeds on stalk

► Maggots enter the bulbs through roots and attack the tender portion.

► Infested plants turn yellowish brown and finally dry up.

► The affected bulbs rot in storage as infestation leads to secondary infection by pathogenic organisms.

♣ Crop rotation should be followed.♣ Application of folidol M 2%@

25kg/ha is beneficial.

Management

Management♣ Spray cypermethrin@ 0.0075%/ deltamethrin@0.0028% or oxy demeton methyl@ 0.025%.

Onion Maggots (Hyleuria antiqua)

☻ Adult appears like housefly.☻ Maggots are small white and devoid of legs.

Mites

☻Suck sap☻Turning plants yellow with sickly appearance.

Management

♣ Infested bulbs should be exposed to sun for 2 days.

♣ Dusting of S @ 22 kg/ha is recommended.