Onion / Bulb onion / common onion belong to the Amaryllidaceae family. It is widely used as a vegetable and also to cook other vegetables. Onion is the basis for most of the cooking in India. Almost all the masalas, chutneys, gravies, curry’s, sambars, rasam and like use onion and tomatoes as the very basic ingredient.
Onions have a huge demand and therefore the supply has to be on par with the demand. Onion is a pungent vegetable and when chopped, it makes your eyes water profusely. The pungency in onions is due to a volatile oil called ally-propyl disulfide. Onion has a lot of nutritional value and health benefits. It can easily be grown in pots, containers and your backyard too. In India, it is cultivated in the states of TN, Maharashtra, AP, Telangana, Bihar, and Punjab. There are many varieties of onions such as red, yellow, and white. Then there are small, medium and large onions available as well in the local markets.
The local names for onions are Pyaaz, Ullipayalu, Vengayam, Eruli, Dungri, Savola, Kandaa, Ganda, Piyavu, Piaja, Tilhou and so on. Onions are an extremely important commercial crop and have a massive worldwide demand. It can be eaten raw, sautéed, cooked, boiled, fried, etc. Onions can be used in curries, salads, raitas, gravies, sambar and so on. It can be used as a flavoring in rice, biryani, pulao, etc. It can be pureed and used as well. Some household remedies for onions include cutting it and keeping it in the house to drive away colds and infections. The bulb of onion consists of swollen bases of green foliage leaves and fleshy scales.
Onion is a cool season crop and cultivated during winter and harvested during the summer season. It can grow well under a wide range of climatic conditions and a wide range of soils as well. It is cooked after peeling the outer layers and chopping it. It can be washed after peeling it as well. Washing also prevents the eyes from watering and helps remove any pesticides that might have been sprayed during cultivation. Onions are high in sugar and hence require being caramelized well before mixing other ingredients in it. That is also what gives the flavor well.
Onions can be stored easily for a week or a two, but depending on the weather conditions, they may become rotten and start getting soft. Onions are stored at normal room temperatures and not in refrigerators. They tend to attract fruit flies and this can be stopped by covering it with a netted lid. There are no particular dishes made from onions, but they form the foundation of each dish. All gravies are made by pureeing onions and tomatoes and then fried and used. They give body to chutneys and other masalas. Some people prefer cooking without onions as they find they kill the taste but all the same, the demand for onions is way too much for it to be ignored.
Image source – asiafarming.com
Types of onions
Image source – theindianspot
India is the second largest producer of onions. The National Horticultural Research and Development Foundation has developed a new variety of onion called the NHRDF-RED-2 that has a good yield. It has been found to have better adaptability and storage performance and is grown in North India. The crop matures in 100 – 120 days after transplanting and its keeping quality are good too. The average yield is 30 – 40 tons/ha.
Onions can be cut into circular rings and served as salads or deep fried with gram flour and served as onion rings etc. They are sometimes chopped and eaten along with the main course as a side to increase flavor. Raw onions are much more beneficial than even the fried ones. Hence the importance of onions has to lead to its increased demand worldwide. Onions are especially known for their antioxidant and antibacterial properties worldwide.
Process of growing Onions
⦁ Time / Season / Climatic Conditions –
Onions grow well in most climatic conditions but are best suited for mild weathers. It cannot withstand anything in excess. Onion is a cool season crop and is mostly cultivated in winter and harvested in summer. It can be grown at an elevation of up to 2000 m between April and August under rainfed conditions.
The best temperatures are 13 – 24 °C for the vegetative stage, 16 – 21 °C for a bulbing stage, and 30 – 35 °C at maturity and harvesting stages respectively.
Onions are grown best in these seasons –
Kharif – May – September
Late Kharif – August – February
Rabi Season – October – April
⦁ Seed Rate / Spacing –
Use only good quality seeds. Seed rate depends on the variety and method of planting. Seeds are sown @ 7 – 9 kg/ha at raised beds of 1.2 m width and 3 – 4m length. The seedlings are ready for transplanting in 45 – 50 days after sowing.
Seeds can be treated with Azospirillum @ 400 gm/kg of seed using rice gruel as adhesive and then dry it under the shade for half an hour and then sow. Apply VAM 1 kg/Sqm in the beds along with 10 kg FYM.
Ridges & furrow type of layout is followed for 15 cm x 10 cm spacing. In case of onion, preferably flatbeds are used because they accommodate more than ridges & furrow, so we get more yield. Also, flatbeds have an equal distribution of water & fertilizers. So we get uniform size & compact bulb of onion which have good keeping quality in storage & transport.
⦁ Soil type / Land preparation / Irrigation –
Onion can be grown on various soils. But sandy loam, silly loam and deep friable soils are best suited for onion crop. The land is prepared by giving 5 – 6 ploughings. The optimum pH range is 5.8 – 6.5. 25 – 30 cart-loads of well rotten FYM or compost applied at the time soil preparation per hectare. For onion 50 kg N, 25 kg P^Os & 25 kg Potash should be applied, as usual method.
Plough the land to get fine tilth by giving 6 – 7 ploughings. Make the land weed free and drain the land of excess water. Add 25 kg FYM. Form ridges and furrows in the field. Zinc sulfate is applied as basal dose @ 50 kg/ha at the time of the last plow.
Maintaining proper moisture content is very important in onion cultivation. Drip or sprinkler method of irrigation is used based on the groundwater availability. Water requirement of the crop at the Initial growth period is less. Irrigation should be stopped 15 – 20 days before attaining maturity for improving the keeping quality of bulbs. Frequent irrigation delays maturity. In Kharif season, depending upon the rains and time of planting 6 – 10 irrigations are enough. In Rabi season, 10 – 15 irrigations are given at bulb formation, irrigation is necessary and moisture stress at this stage results in low yield.
Sufficient irrigations are required at the bulb forming stage. Irrigation is necessary at the time of dibbling or transplanting of cloves onions require frequent irrigation because of the shallow root system. Excess irrigation leads to the plants becoming yellowish. Onions require 30 inches of irrigation during growing season. If there is not enough water, onions will not get a huge bulb. When the neck starts falling, the onion matures, and irrigation is discontinued.
⦁ Weed management / Pest Control –
Cultural Operation keeps the field absolutely free from weeds to produce a good crop of onion. Weeds if not controlled in an early stage will injure the onion bulbs and the yield will be poor. 2 – 3 hoeing and weedings are enough for the crop. After 2 – 3 irrigations, earth up the poor plants.
For transplanted onion, pre-emergence application of Oxyfluorfen @ 0.15 – 0.25 kg/ha or Fluchloralin @ 1kg/ha or Pendimethalin 3.5 l/ha with one hand weeding in both seasons
For onion nursery and direct seeded crop, application of Pendimethalin 3.5 l/ha just after sowing
Thrips and onion fly are controlled by spraying Methyl demeton 25 EC 1 ml/lit or Dimethoate 30 EC 1 ml/lit with Teepol 0.5 ml/lit
Cutworm is controlled by drenching the soil Chlorpyriphos @ 2 ml/liter
Nematode is controlled by applying Carbofuran 3 G 1 kg/ha or Phorate 10 G 1 kg/ha @ 10 days after transplanting
Leaf spot can be controlled by spraying Mancozeb 2 g/lit or Copper oxychloride 2 gm/liter of water. Add 1 ml of Teepol to 1 liter of the spray
Crop rotation also helps control weeds
⦁ Harvesting –
Follow harvesting of onion bulbs at the right stage of maturity. It is important in deciding storage life of onion as bulbs may be stored for about six months. The onion bulbs, reach maturity when the plants cease to produce new leaves and roots. In onion, neck fall is the indication of maturity. Time of harvesting depends on several factors tike planting season, cultivar, market price and condition of the crop. In general, when about 50 % neck fall is seen, the crop is harvested. Onion for storage should be fully developed. Thick-neck bulbs which result due to premature harvesting do not store well.
Bulbs are harvested by hand pulling if the soil is light. They are also harvested by hand implements. Onion along with tops are kept in the field for 2-3 days, curing for 3-4 days is necessary to remove excess moisture from outer skin and neck to reduce shrinkage and development of color in storage.
Kharif season yield – 15 – 20 t/ha, late Kharif season yield – 30 – 35 t/ha, Rabi season yield – 25 – 30 t/ha
⦁ Benefits of raw onions –
Raw onions lower the LDL (bad cholesterol) levels and keep your heart healthy.
⦁ The ⦁ vitamin C content along with the phytochemicals present in onions helps build immunity.
⦁ Quercetin, a powerful compound found in onions, has been suggested to play a role in preventing cancer, especially stomach and colorectal cancers.
⦁ Chromium helps regulate ⦁ blood sugar levels.
⦁ A mixture of onion juice and ⦁ honey is said to be effective as a cure for fever, common cold, allergies, etc.
⦁ Keep a small piece of onion under the nostrils and inhale, to stop or slow down a nosebleed.
⦁ Folate in onions also helps with ⦁ depression and aids sleep and appetite.
⦁ The vitamin C helps the formation of collagen that is responsible for ⦁ skin and hair health.
⦁ Freshly chopped raw onions have anti-bacterial properties
Chewing raw onions improves oral health and eliminates bacteria that can lead to tooth decay and gum issues.
Nutritional Composition of Raw Onions
One cup of chopped onion contains approximately:
a) 64 calories
b) 15 grams of carbohydrate
c) 0 grams of fat and cholesterol
d) 3 grams of fiber, 2 gm protein
g) 7 grams of sugar
h) 10% or more of the daily value for vitamin C, vitamin B-6 and manganese.
i) They also contain small amounts of calcium, iron, folate, magnesium, phosphorus and potassium and the antioxidants quercetin and sulfur.