Onion Cultivation: A Comprehensive Guide To Successful Harvests

Onion (Allium cepa) is an important root vegetable, serving as a staple ingredient in many Indian dishes. It is a member of the Allium family, which also includes garlic, leeks and chives. They are known for their pungent flavor and aroma, which are caused by sulfur-containing compounds. India is one of the largest producers of onions in the world, with the states of Maharashtra, Karnataka and Gujarat being major onion-growing regions. India produced about 32 million metric tons of onion in the year 2022. Total area under its cultivation in 2022 is 1.94 million hectares. The demand for onions in India is high, and the crop is an important source of income for many farmers in the country.  

Soil Requirement

Almost all soil types are suitable for onion cultivation. However, sandy loam to clay soil with good drainage, moisture holding capacity and rich in organic matter is considered ideal. Optimum soil pH for its growth is 6 – 7.5. Onion is sensitive to highly acidic, saline and alkali soils. Avoid waterlogging in the field. 

Season and Time of planting

Varieties of onion

Different Methods of Growing Onions

Onions can be grown in three different methods depending upon the purpose of their cultivation. 

1. Seed sown in nursery and then transplanting the seedlings in mainfield 
2. Raising small bulblets for green onion production 
3. Broadcasting or Direct sowing 

1. Nursery Management

Onion seeds are generally sown in nursery beds.  

Preparation of nursery bed: For 1 acre main field, 0.05 acre i.e., 200 m2 of nursery area is required. Apply 200 kg of FYM mixed with 2 litre of Trichoderma harzianum at the time of last ploughing helps in controlling damping off, root rot, collar rot and other soil borne diseases. Prepare raised beds of 1 – 1.2 m width, 10 – 15 cm height and of convenient length. Maintain 70 cm distance between the beds.  

Seed rate: 3 – 4 kg seeds are required for 1 acre field. 

Seed treatment: Before sowing, treat the seeds with Bavistin at 2 gm/lit of water for 1 kg seeds or in bio fungicide by mixing 8 – 10 gm of Trichoderma viride in 50 ml of water for 1 kg seed to prevent damping off and other diseases. 

Sowing: Sow the seeds in line at 5 – 7.5 cm apart at 1 cm depth. After sowing, cover the seeds with fine soil, powdered FYM or vermicompost. Give light irrigation. Drip or sprinkler systems of irrigation can be adopted. Cover the beds with paddy straw or sugarcane leaves or grass to improve germination by maintaining required moisture and temperature. Drench the soil bed with Carbendazim 50% WP at 0.5 – 0.75 gm/lit water to prevent damping off. Add 0.5 kg/bed of 15:15:15 (NPK) after 10 days of sowing, if seedlings show nutrient deficiency symptoms. Mulched grass or straw can be removed after germination is completed.  

2. Raising small bulblets for green onion production

This method is used for production of green onions/bunching onion which have demand for salad in early winter. For this, take small onion bulblets of kharif onion varieties raised in previous season for planting. Prepare raised beds or flat beds depending upon soil type (Raised bed – heavy soil; Flat bed – sandy soil). 15 grams of seeds are sufficient for 1 m2 area of bed i.e., 3 kg seed is required for total nursery area. Sow them in mid Jan – Feb starting to get quality bulblets. Leave the plants in nursery bed up to April to May till their top fall. Harvest the tops and selected bulblets and store them by hanging method till July. These stored small bulbets can be used for transplanting in the kharif season for raising green onion. 

3. Broadcasting/Direct sowing

Seed rate: 8 – 10 kg/acre; Time of sowing: Sept – Oct 

In case of big onion, sow the seeds in lines at 30 cm apart (30 cm within row and 30 cm between plants). Later, thinning can be done to give proper spacing for bulb development. In case of small onion, broadcast the seeds in small flat beds. Do hand hoeing after sowing the seeds to allow seeds to reach 2.5 – 3 cm depth. Give light irrigation. At 10 days interval, weeding can be done. 

Land preparation for main field 

Plough the field to a fine tilth and add 10 t of FYM at the time of last ploughing. Flat beds or broad bed furrows can be formed for transplanting the seedlings. Prepare flat beds of 1.5 – 2 m width and 4 – 6 m length. For broad bed furrows, prepare beds of 120 cm width and 15 cm height with 45 cm furrow spacing between two beds. Irrigate the beds before transplanting seedlings.  

Transplanting of seedling from nursery 

Seedlings raised from seed sown nursery will be ready for transplanting within 6 – 7 weeks of sowing for kharif and 8 – 9 weeks for rabi. Transplant the seedlings with a spacing of 15 cm between the rows and 10 cm between the plants.  

Fertilizer Requirement for Onion Crop

The general dose of fertilizer recommendation for onion is 60:24:24 kg/acre. 

Water Management 

Onion is mainly grown as an irrigated crop. Frequency of irrigation depends upon the climatic conditions and soil type. Irrigate the field at the time of transplanting the seedling. Give another irrigation on 3rd day after transplanting. Then, depending upon the soil moisture irrigate at an interval of 10 – 15 days. Stop irrigating the field 10 days before harvest. Avoid over watering or less watering as it may affect onion growth and development. Drip or sprinkler irrigation systems can also be adopted. 

Weed Management 

It is important to keep the field free from weeds during the initial growth stages.  Apply Oxyfluorfens 23.5% E.C at 200 ml/acre followed by one hand weeding 45 days after transplanting for effective weed management.  

Crop Rotation and Mixed cropping 

Onion can be grown as an intercrop with sugarcane during the initial 5 months after planting sugarcane. They can be rotated with legumes, corn, brassica and solanaceous crops. Onions are heavy feeders and can quickly deplete the soil of nutrients. Rotating onions with legume crops can help to replenish the soil with nitrogen. Corn, on the other hand, is a non-host for onion pests and diseases, which can help to reduce the build-up of these problems in the soil. Similarly, rotating brassica and solanaceous crops with onions can help to maintain soil health and prevent the build-up of pests and diseases. 

Plant Protection Practices 

Pests of Onion crop 

Diseases in Onion crop 

(Note: Check the product’s label before application to know the right time of application.) 

Harvesting 

Time of harvesting depends on the purpose for which the crop was planted. For dry onions, harvesting can be done in 5 months while for green onions, harvesting can be done in 3 months after harvesting. For harvesting rabi onion, the indication is 50% of neck/top falling over. Harvesting is done by manually uprooting the bulbs. But for kharif seasons, since the top does not fall over, the sign of harvest is change in colour of leaves to slight yellow and red pigmentation on bulbs. During hot days when soil is hard, use hand hoe to pull out the bulbs. Spray the crop with Carbendazim 2 gm/lit of water which will help harvested onion protect from any kind fungal infections after harvest. 

Curing 

After harvesting, onions need to be cured to prolong the shelf life, for proper development of skin colour and remove field heat before storage. For curing, spread them out in the field without direct exposure to sun by covering the onion bulbs with foliage of other bulbs in small heap.  Allow the onions to dry for 3 –5 days, until the leaves and stems are completely dry and brittle. After complete drying, cut the leaves leaving about 2 – 2.5 cm tops above the bulb.  

Storage 

Once the onions are cured, they can be stored in a cool, dry location. It is important to store them in a well-ventilated area to prevent mold and rot. Onions can be stored for several months if they are properly cured and stored.  

Yield 

8 – 10 t/acre.