Onion crop – Interesting facts | Agristudent.com

 

Onion is an important crop. Given below are some interesting facts about onions –

Indian onions are famous for their pungency and are available round the year

The botanical name of Onion is Allium cepa

The family of Onion is Alliaceae

The origin of Onion is Central Asia

Chromosome number of onion crop os 2n= 16

Red colour in onion is due to a pigment called Anthocynin

Prrsence of pyruvic acid caused eye burning during cutting of onion

Onion is a rich source of vitamin B

The edible part of onion is called Bulb

The agriculture revolution associated with Onion is – Pink revolution

The outer skin colour of onion is due to a pugment called Quercetin

Onion is highly cross pollinated crop

Cross pollination in onion is maily brpught about by Honey bees

The phenomenon whoch gives rise to cross pollibation in Onion is Protandry (maturing of anthers of onion flowers before stigma)

The pungency in onion is associated with the presence of alkaloid called – Allyl propyl di sulphide

Onion is anti fungal due to the presence of anti fungal compound called Catechol

Major research in India is carried out in research centre called Directorate of research on Onion and Gatlic located at Pune

India is the second largest onion growing country in the world. (First is China)

Country which ranks first in export of onion is  Netherlands (India ranks 4th)

State of Maharshtra ranks first in Area and production of Onion in India

The biggest onion market in the world is located at Lasalgaon in Maharashtra

 

Indian onions are famous for their pungency

The bulb of onion can be white, yellow, or red

The bulb of onion requires 80 to 150 days to reach harvest.

The major Onion producing states in india are Maharashtra, Madhya Pradesh, Karnataka, Gujarat, Rajasthan, Bihar, Andhra Pradesh, Haryana, West Bengal, Uttar Pradesh, Chhattisgarh, Odisha, Jharkhand and Telangana

Onion is a temperate crop but can be grown under a wide range of climatic conditions such as temperate, tropical and subtropical climate.

Onion plant, in the young stage can withstand freezing temperature also.

In India, short-day onion is grown in the plains and requires 10-12 hours day length.

The long-day onion is grown in hills requiring 13-14 hours day length.

For vegetative growth – lower temperature and shoet photoperiod is required

For bulb development – higher temperature and longer photoperiod is required for bulb development and maturity.

The optimum temperature for vegetative phase and bulb development is 13-24˚C and 16-25˚C, respectively.

Bolting in onion is caysed by lower temperatures of less than 12 degree celcius

Onion requires about 70% relative humidity for good growth.

Rainfall required for onion growth is 650-750 mm with good distribution during the monsoon period.

The best soil for successful onion cultivation is deep, friable loam and alluvial soils with good drainage, moisture holding capacity and sufficient organic matter.

In heavy soils, the bulbs produced may be deformed.

The optimum pH range, regardless of soil type, is 6.0 – 7.5

Onions do not thrive in soils having pH below 6.0 because of trace element deficiencies, or occasionally, Al or Mn toxicity

Varieties of onion are

Small Common Onion – Agrifound Rose, Arka Bindu

White Onion – Bhima Shubra, Bhima Shweta, Bhima Safed, Pusa White Round, Arka Yojith, Pusa White Flat, Udaipur ­102, Phule Safed, N­257­9­1, Agrifound White.

Spanish Brown – Bhima Light Red, Bhima Kiran, Phule Suvarna, Arka Niketan, Arka Kirthiman

Red onion – Bhima Super, Bhima Red, Bhima Raj, Bhima Dark Red, Bhima Shakti, Punjab Selection, Pusa Red, N­2­-4­-1, Pusa Madhavi, Arka Kalyan, Arka Lalima.

Sowing method

Onions can be grown from seeds, seedlings and bulblets.

About 0.05 hectare nursery bed area is enough for getting seedlings to transplant in one hectare.

For raising nursery, raised bed of 10-15 cm height, 1.0 – 1.2 m width and length as per convenience may be prepared.

The distance between beds should be at least 30 cm, so that water movements are uniform and drainage of excess water is possible.

Raised bed is recommended for nursery because in the case of flat bed, water moves from one end to the other and there is a possibility of washing away of seeds.

Application of pre-emergence herbicide pendimethalin @ 0.2% is recommended to control weeds in nursery.

About 5-7 kg seeds are required to raise seedlings for one hectare.

Before sowing, seeds should be treated with thiram @ 2 g/kg of seed to avoid damage from damping off disease.

Application of Trichoderma viride @ 1,250 g / ha is also recommended to manage damping off and raise healthy seedlings.

Seeds should be sown in lines at 50 mm to 75 mm apart to facilitate the removal of seedlings for transplanting, quick weeding, spray of pesticides etc.

Foliar spray of benomyl @ 0.2% is recommended to control soil borne diseases in the nursery.

When the severity of thrips infestation is high, foliar application of Fipronil or profenopos @ 0.1% is recommended.

Seedlings are available for transplanting in 35-40 days after sowing (DAS) for Kharif and 45-50 DAS for late Kharif and Rabi seasons.

Raising small Bulblets

This method is used for getting early crop in the kharif season so as to meet the demand of green onion for salad in early winter – small bulblets method of raising is used

For bulblets method of raising, small onion bulblets of kharif onion varieties like Agrifound Dark Red, Baswant 780, N-53 and Arka Kalyan raised in the previous season are used for planting.

To cover one square metre area of the bed 15 g of seed are sufficient in bulblets method.

The best time of sowing of seeds for getting quality bulblets is mid January to the beginning of February depending upon the area.

Seeds of small onion (Bangalore Rose, Agrifound Rose and Arka Bindu) are broadcasted in small flat beds which are thinned later for allowing space for bulb growth.

For broadcasting directly in the field or sowing in the row, 20-25 kg seeds per hectare are used.

In the plains, seeds are sown (Direct sowing method) in lines 30 cm apart during September-October.

After sowing, hand hoeing is done to allow the seeds to reach to a depth of 2.5-3 cm.

Weeding is recommended at 10 days interval for preventing smoothering of seedlings by weeds.

Organic manures equivalent to 75 kg N/ha (approximately FYM 15 t/ha or poultry manure 7.5 t/ha or vermicompost 7.5 t/ha) should be incorporated at the time of last ploughing and beds with appropriate size should be prepared after leveling.

Water logging favours Anthracnose disease which is most devastating during Kharif season.

Broad bed furrows (BBF) of 15 cm height and 120 cm top width with 45 cm furrow are formed to achieve proper spacing and population density.

BBF is the best method for Kharif onion production because the excess water can be drained out through the furrow. This improves the aeration and helps in reducing the incidence of Anthracnose disease.

At the time of transplanting, one third of the seedling top should be cut to get good establishment.

The onion seedling should be transplanted after dipping roots in carbendazim solution (0.1%) for two hours to reduce the incidence of fungal diseases during the establishment.

The optimum spacing is 15 cm between the rows and 10 cm between plants.

Manuring and fertlization

Fertilizer schedule for onion (per ha)

Schedule

N

P2O5

K2O

Organic manures

Kharif onion (Yield potential – 25-30 t/ha)
Basal

25 kg

40 kg

40 kg

Organic manures equivalent to 75 kg N

(FYM – Approx. 15 t/ha or

Poultry manure- Approx. 7.5 t/ha or

Vermicompost – Approx. 7.5 t/ha)

30 DAT

25 kg

45 DAT

25 kg

Total

75 kg

40 kg

40 kg

Late Kharif and Rabi onion (Yield potential- 40-50 t/ha)
Basal

40 kg

40 kg

60 kg

Organic manures equivalent to 75 kg N

(FYM – Approx. 15 t/ha or

Poultry manure- Approx. 7.5 t/ha or

Vermicompost – Approx. 7.5 t/ha)

30 DAT

35 kg

45 DAT

35 kg

Total

110 kg

40 kg

60 kg

Long day onion (Yield potential-100 t/ha)
Basal

60 kg

60 kg

70 kg

Organic manures equivalent to 75 kg N

(FYM – Approx. 15 t/ha or

Poultry manure- Approx. 7.5 t/ha or

Vermicompost – Approx. 7.5 t/ha)

30 DAT

60 kg

60 DAT

60 kg

Total

180 kg

60 kg

70 kg

One third of recommended N and full dose of P2O5 and K2O are applied at the time of planting while remaining two third N is applied in two equal splits at 30 and 45 days after planting.

In addition to NPK, sulphur is also an essential plant nutrient important for onion crop for improving yield and the pungency of onion bulbs.

Sulphur is recommended as basal dose at the time of transplanting.

Application of 15 kg sulphur/ha is sufficient for growing onion crops in soils having sulphur level above 25 kg/ha while 30 kg sulphur/ha is needed for soils having sulphur level below 25 kg/ha for optimum production of onion.

Soil application of 50 kg S /ha is recommended for long day onion crops.

Application of Oxyflurofen @ 23.5% EC (1.5 -2.0 ml/L)/ Pendimethalin @ 30% EC (3.5-4ml/L) before transplanting or at the time of transplanting followed by one hand weeding at 40-60 days after transplanting is recommended for efficient weed control.

Rotation and Mixed Cropping Onion crop should follow the vegetable crops such as cauliflower, tomato and potato, which require large quantities of organic manures.

As a winter crop, it follows cereals, groundnut and cowpea while as a summer crop it follows paddy.

When cultivated as monsoon or late monsoon crop, coriander, french bean, sorghum, pearl millet, chillies, and groundnut are planted after harvesting onion.

During the initial five months after planting sugarcane, onion is grown as an inter-crop.

In general, onion needs irrigation at the time of transplanting, three days after transplanting and subsequently at  7-10 days interval depending upon the soil moisture.

In general, Kharif crop needs 5-8 irrigations, the late Kharif crop requires 10-12 and Rabi crop needs 12-15 irrigations.

Onion being a shallow rooted crop, needs frequent light irrigation to maintain optimum soil moisture for proper growth and bulb development.

Irrigation needs to be stopped when the crop attains maturity (10-15 days before harvest) and the top starts falling which helps in reducing the rotting during storage.

In case of drip irrigation, seedlings need to be planted at a spacing of 10 x 15 cm in a broad bed furrow (BBF) of 15 cm height and 120 cm top width with 45 cm furrow.

Each BBF should have two drip laterals at (16 mm size) 60 cm distance with inbuilt emitters.

The distance between two inbuilt emitters should be around 30-50 cm and the discharge flow rate is 4 l/hr.

In case of micro sprinkler, the distance between two laterals (20 mm) of micro sprinkler should be 6m with a discharge rate of 135 l/hr.

The research outcome indicated that the drip irrigation significantly improved the marketable bulb yield (15-25%) with higher per cent A grade bulbs, water saving of about 35-40% and labour saving of 25-30% as compared to flood irrigation.

Application of fertilizers @ NPK 40:40:60 kg /ha as basal and the remaining 70 kg N in seven splits through drip irrigation is recommended for achieving higher marketable bulb yield and cost benefit ratio.

0nion crop is ready for harvesting in five months for dry onion.

For marketing as green onion, the crop becomes ready in three months after transplanting.

When the bulbs developing from the leaf bases of onions are fully formed, the leafy green tops begin to yellow and eventually collapse at a point a little above the top of the bulb, leaving an upright short neck. When the tops “go down” in this way, the bulbs are ready for harvesting.

Because all the onions in a crop do not mature at the same time, large-scale commercial growers harvest them when about half the tops have gone down.

In kharif season, since tops do not fall, bulbs are harvested soon after the colour of leaves changes to slightly yellow and red pigmentation on bulbs develop.

Best time to harvest rabi onion is one week after 50% tops have fallen over.

Onions for sale as dried bulbs or for storage should be harvested progressively after tops have started falling over.

Irrigated onion crop in rabi season gives an yield of 25-30 t/ha while under rainfed conditions it yields only about 0.7-1.0 t/ha.

Onion raised as an intercrop in sugarcane and turmeric, in alleys of young fruit garden and banana garden, gives a yield of 5-9 t/ha.

The small sized, pungent, local cluster type onion yields half as compared to the large sized varieties.

Onions are stored in a well-ventilated place with lot of aeration and sunlight.

Onion bulbs are packed in perforated gunny bags and stalked in vertical column, one above the other. However, height of such vertical column should not exceed more than 5 feet and should have sufficient space all around and bottom.

Onions are dehydrated at 2 percent moisture (Dehydration ratio)

References

Vikaspedia.in

Handbook of horticulture

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