Onion Allium cepa belongs to the family Amaryllidaceae. Onion is a bulbous plant with the bulbs and leaves are semi-cylindrical or tubular with waxy coating on the surface.
Onion Growing season and Planting time:
Onion in India is cultivated by farmers of almost all states as both Kharif and rabi crop synched with geographical location and weather based.
Almost all soils such as heavy soil, clayey soil, sandy loam, etc are suitable for onion growing. Red to black loamy soil with good drainage is best suited and ideal. Soil must be friable with lots of organic matter and good water holding capacity.
So, adding organic matter during preparation of land in the form of compost or farm yard manure or well decomposed poultry manure is more important. Soils with pH range of 6.0 to 7.0 is more ideal and onions cannot survive beyond the range.
Usually three types of onions are grown commercially in India like White, Yellow and Red.
Varieties: At the following link the seed varieties can be viewed. Few of them are Nasik Red, Prerana,XP Red onion, Gulmohar, Prema Onion, Marshal onion ,..etc.
Seedling transplanting: 2 - 2.5 kg/acre; - Spacing for seedling transplanting: 15 cm x 7.5 cm
Direct sowing: 8 – 10 kg/acre; Spacing - 30 cm x 30 cm
Broadcasting: 20 – 25 kg/acre Spacing - 30 cm x 30 cm
The onion seeds are transplanted in the nursery in about 35 – 40 days. Before transplanting the land should be ploughed to fine tilth, decomposed farm yard manure 8 tonnes or vermicompost 4 tonnes fortified with biofertilisers 5 kg and biological agent Multiplex Biojodi 5 kg should be incorporated in the soil.
The land can be prepared to flat beds or ridges and furrows based on the seasons. Flat beds with size 1.5 to 2 m width and 4 to 6 m length or broad bed furrows with 15 cm height and 120 cm top width may be prepared. The furrows should be 45 cm deep so that proper drainage is ensured.
The onion seedlings nursery of 0.12 acre land is required to raise for one acre of onion crop. Prepare nursery beds of size 7.5 m length, l.2 m width and 10cm height. Add 3 - 4 basketful of FYM/compost, 200g BACILLUS + PSEUDOMONAS (Multiplex Biojodi) and Bio activator mixtures (Ecohume Gr granules) per bed.
Mix all the above products well & incorporate into the soil. Sow the seeds in the rows of 7.5 cm apart to facilitate the easy weding and uprooting during transplanting. Seeds after sowing need to be covered with soil or farm yard manure and irrigate the beds immediately. Again after 10 days add 0.5 kg/bed 15:15:15 (N:P:K). Seedlings will be ready for transplanting within 6- 8 weeks after sowing. Then transplant the seedling at 15 cm x 7.5 cm spacing.
Direct seeds sowing: After thorough land preparation directly sow the seeds in a row of 30 cm apart and 30 cm between plants.
Broadcasting: Broadcast the seeds after land preparation and Basal applications. Thinning may be required at highly populated dense growth of the onion saplings.
Onion plants are transplanted to main filed at the age of 35 - 40 days. During transplantation proper care is taken and should avoid over aged seedlings.
Some of the important factors need to followed during transplanting.
- About one-third of the top of the seedling is cut
- Roots are dipped in 2 gm Metalaxyl 35% [Krilaxyl Power]solution for two hours to prevent fungal diseases
- The seedlings are transplanted into prepared beds at a distance of 10 – 15 cm between plants.
Water requirements for Onion crop
Onion crop requires water or moisture to survive and grow. Irrigation for onion crop starts from immediately of seedling plantation or sowing and 3 days after planting or sowing. Subsequently the irrigation in regular intervals need to be provided to supply proper moisture for growth and development of onions. Over watering, less watering supplying irregular with dry spells will harm onion growth and development. Supply of irrigation abruptly to onion crop, the bulbs may develop splitting and reduce the crop quality. The last irrigation to the onion crop must be stopped 10 days before harvest.
Recent techniques of irrigation like sprinkler, drip may be adopted to supply proper watering to the onion crop as they will help maintaining required ideal moisture level in soil.
Recommended dose of Fertilizer Application: NPK – 50:30:40 kg/ per acre per crop
6 to 8 ton of FYM applied at the time of soil preparation per acre along with 20 kg N, 20 kg P2O5 & 20 kg Potash /acre should be applied along micro nutrient 5 kg Zinc high Aries Multi Micronutrient fertiliser + 15 kg Calcium nitrate.
Remaining 20 kg N + 10 kg P and 20 kg Potash to be applied after a month of sowing and another 10 kg of N 20- 25 days before harvest.
A. Diseasesa. Viral Infections
Onion Yellow Dwarf Virus Disease – transmitted by aphids
- The virus infected leaves develop yellow streaks that spread progressively leading to yellow leaves.
- Highly infective leaves curl and plants will
- Onion bulbs in infected crop fail to grow to full size
Irish Yellow Spot Virus - transmitted by Thrips
- Spindle or diamond shaped straw coloured lesions are observed on the leaves.
- These lesions may also be in green with yellow borders
- At flowering stage, the flower stalks may be infected.
Management of Viral infections
- Viral diseases resistant varieties may be grown
- Planting material for sowing must be of good quality with free of insects and diseases
- Avoiding aphids and thrips infestation through inter-cropping
- Growing stress free onion crop avoid the viral infections
- Crop rotation in virus infected fields is advised
- Spraying insecticides to kill and manage the aphids and thrips
- Damping Off - Water soaking/ More moisture at root zone and Pythium spp.
- Transplanted or sowed seeds will topple off
- The disease may be rottening of the young stems above the ground, appear as soft water-soaked spots.
Sowing or transplanting on the raised beds
Drenching with Metalaxyl 35% [Krilaxyl Power]
2. Stemphylium blight – caused by Stemphylium vesicarium
- Small flecks of yellow to orange colored develop in the middle of the leaf
- Small flecks grow to form elongated; spindle shaped to ovate, diffused spots
- Larger developed spots will be surrounded by pink margin
- Usually the spots progress from the tips and uncontrolled severe infections display the patches.
3.Purple Blotch – Caused by Alternaria porri
- Infection of purple blotch starts from older leaves, tips with small elliptical lesions turns to purple brown on development.
- The spots will be surrounded by chlorotic margins and severity may girdle the leaves and even they may fall off.
4. Anthracnose (twister disease) – Caused by Colletotrichum gleosporiodes
- Infected with anthracnose disease the stems or necks will abnormally elongates
- The leaves will also get curled and twisted with water soaked pale yellow patches on the baldes
- Black coloured structures appear around the centre of the leaf
- Botrytis fungus causes Neck rot, gray mold, or leaf and flower blast of onions and garlic.
- Downy mildew of onion is caused by Peronospora destructor
Management of above fungal infections
The above fungal infections may be controlled by spraying any of following insecticides.
- Sucking Insects
Thrips and Aphids
Thrips (Thrips tabaci)- Adult thrips which are yellow to black in color with 4 wings and immature thrips have white color body with no wings will harm onion plants in growth stages up to 45 days from sowing or transplanting. The aphids also will infest the onion crops in colonies sucking the plant sap in onion leaves.
- The thrips infested leaves will be twisted and curled, show silver coloured patches in severe infestations and tip burn is noticed.
- The aphids infested plants show sticky appearance on the onion leaves and sooty mould is also visible in severe attacks
The molecule listed below may be used in the management of above pests
Pink or pinkish purple microscopic mites will infest the onion leaves.
- The leaves may turn yellow mottled at the edges.
- The leaves curl up and may not open up completely
Harvesting of onion is done the green tops start drooping. 10 days after stopping irrigation the harvesting is initiated. The plants are gently pulled out from the soil and leave on the soil for drying for about 4-5 days.
The crop should be sprayed with carbendazim 2 gm/L of water will help harvested onion protect from any kind fungal infections after harvest.
K SANJEEVA REDDY,
Senior Agronomist, BigHaat.
For more information kindly call on 8050797979 or give missed call on 180030002434 during office hours 10 AM to 5 PM
Disclaimer: The performance of the product (s) is subject to usage as per manufacturer guidelines. Read enclosed leaflet of the product(s) carefully before use. The use of this product(s)/ information is at the discretion of user.
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