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Onions (Allium cepa)

Local names in Kenya (Kitungu; Otungu; Esitinguo)



Onion is a biennial vegetable, but some varieties are grown as annuals. In the tropics the varieties that do well are in effect annuals as they can produce seed within the first year of growing. In general, onions are used for salads bunching onion or sliced full-grown bulbs, marinating e.g. silver skin onions, cooking such as in soups and frying e.g. with meat. Onions are particularly suited to smallholder farming. It also plays an important role in traditional medicine e.g. as a diuretic. Onion is rich in Calcium, Iron, Vitamin B, and Vitamin E and has therapeutic properties. In tropical climate onion can be grown all year-round where irrigation is possible.

Red bulb onion.


Site selection
Site selected should be open and without shade. 

Altitude range

Onion require altitudes of 500-2000 masl

Soil type and conditions

Well-drained, deep, fertile, clayey loam and sandy loam soils with good water holding capacity, away from shade.

It requires a pH of 6.0-7.0 (6.5-6.8) and lime can be applied if the pH is below 5.0. Onion nutrient requirements include: N, P, K, Mg, S, B, Zn, Mo, Mn

Temperature range

The temperatures should be 15 – 30 oC


The rainfall should be 500 – 700 mm p.a

Well distributed and with a dry season prior to harvesting


Land preparation
Prepare seedbed to appropriate tilth 

Steps during land preparation

  1. Deep plough and rip the land to give room for bulbing and to break hardpan
  2. Harrow to appropriate tilth just before planting
  3. Apply well-decomposed manure and mix with the soil, based on soil analysis results 
Planting materials: Seeds, Setts or bulbs 

Use clean, disease-free bulbs or sets for planting, from registered agro -input outlets.


Onion seeds and seedlings

Vegetative stage

Reproductive stage


Select a variety that is suitable and adapted to specific altitudes 

Available varieties include;

SP 7030NS, Jambar F1, Red creole, Red Pinoy F1, Red passion F1 and Red comet F1

Nursery Practices
Seeds can be planted directly into the seedbed or raised in the seed nursery 

Prepare nursery beds 1 m wide by any desired length

Onion seed bed


Prepare seedbed to appropriate tilth. Can be sunken nursery beds in dry areas flat or raised nursery beds in high rainfall areas and use boxes or trays filled with appropriate rooting media

Dress the seeds before planting in the nursery to control fungal diseases

Make drills of 15 cm apart and 5 cm deep; Mix the seeds with dry sand at ratio 1:3. Seed rate: 1-1.5 kg per acre

Sow seeds and cover lightly; irrigate lightly; provide shading or mulch

Seedlings will be ready 6-8 weeks, at pencil thickness

Prune the seedling leaves before transplanting, to harden the seedlings for transplanting

Uproot seedlings only when ready to transplant

Water the nursery bed prior to pulling out the seedlings 

Carefully pull out the seedlings to avoid damage


Planting Is done through direct seed planting using setts and seedling transplanting 


Direct sowing

Direct sowing gives excellent results where the season is sufficiently long to provide early pre-bulbing growth. Direct sowing at rate of 2-4 kg per ha at 30 cm apart

Drill 2.5 cm deep and 30 cm apart across the field


Planting using setts


Bury the onion setts up to only one inch under the soil. Thin after 4-6 weeks 1-1.5 months to 8-10 cm x 30 cm spacing depending on the use for medium sized onions

Planting can be spaced 7.5-8 cm within row. When smaller onions for use in pickling or boiling are desired, spacing can be reduced to 2.5 cm in the row. Larger bulb size is promoted by spacing of 10 cm or more


Transplant seedlings at 3-5 true leaves or pencil thickness and 10-15 cm tall, at a spacing 30cm between rows and 8-10 cm between plants for medium-sized bulbs.

Cut off 50 per cent of the green tops to harden the transplant and hasten take off

Water or irrigate immediately after transplanting and regularly until the seedlings get established


Water management
Irrigate moderately at the growing stage in the morning or evening if rainwater is not sufficient. 


Lighter soils need more frequent water applications but less water applied per application

Increase amount of water at the bulbing stage reduce and discontinue watering towards bulb maturity

Stop irrigation 15-20 days prior to harvesting


Weed management
Weed control should be timely and unearth during weed control by hand 


Hand weeding done 2-3 times depending on the condition of the field 

Use inorganic mulch polythene and organic grass mulch or selective herbicides


Soil fertility
At planting apply amounts of phosphate fertilizer depending on soil analysis results. The recommended rate is 200kg per ha TSP at planting 


Top-dress with 300kg per ha CAN or applicable N fertilizer 3-4 weeks after transplanting and same quantity 6 weeks after transplanting based on soil analysis report

Watering should be done immediately after topdressing

Second top-dress fertilizer at 7-8 weeks after transplanting at same rate as first top-dress

Strip or banding method is preferred over broadcasting as it is more effective. Too much nitrogen results in thick necks

Top-dressing should be completed before initiation of bulbing


Crop management
Thin and remove the soil around the bulb 


If the soil is hard, loosen or remove excess soil around the bulbing point to allow bulbs to expand/ develop well. Take care not to damage or expose the roots


Pest management
Check for pests; apply biological control using natural enemies and botanical methods 


Pests include;

Onion thrips (Thrips tabaci) and Onion fly (Delia antiqua), Cut worms, Aphids, Leaf miners (Liriomyza spp)


Onion thrips

Thrips thrive in dry conditions, moist plants drive them away. Adult thrips are small 0.5-2.0 mm, slender and winged 

Wings are long and narrow and fringed with long hairs Nymphs are white or yellow. Both adult and nymphs feed on the base of the plant within the leaf sheaths


Onion fly maggots

These measure 8 mm long and are white cream in color; They are the most destructive stage of the fly


Cut worms




Leaf miners


Pest Control Strategies

IPM and crop rotation

Proper soil management and field sanitation

Rogue infested plants

Weeding and irrigation of water stressed plants that are more susceptible to thrips

Biological control using natural enemies and botanical methods e.g. Neem extracts can be sprayed on plants attacked by onion thrips

Use well decomposed manure or compost S

pray with recommended pesticides


Disease management
Check for disease; spray with suitable fungicides as instructed 


Major diseases include;

Purple blotch (Alternaria porri), Downy mildew (Peronspora destructor), Rust (Puccinia porri), )Onion smuts and Soft rots

Purple blotch


Downy mildew




Onion smuts


Soft rots

Disease control strategies

IPM and Good agronomic practices e. g.  right spacing

Use clean seed or planting materials and varieties tolerant to major diseases

Timely harvest and crop rotation

Spray with suitable fungicides, as recommended/instructed

Field hygiene e.g. destroy infected crop residues


Onion mature in 3 months after transplanting 


Bulb onions are ready for harvest when: they are 3 months old after transplanting 75% of the tops have turned brown or yellow, fall over and dry

Eaves start to turn yellow and the skin becomes papery around the bulb, foliage wither and form a shiny membrane cover around the bulb, the neck of the onion is dry and tight

The silver skin peels off easily, 50% of the bulb is exposed out of the soil neck falls

The green onions can be harvested during thinning after 45-60 days and used as salads. Harvesting is done when leaves begin to turn yellow and bulbs are firm


Onion are ready for harvesting when they are 3 months old after transplanting 


Harvesting is done manually in Kenya during hot and sunny days by levering the bulbs with a fork to loosen them and pulling the tops gently by hand to avoid bruises

To prevent sun scald the bulbs are laid in such a way that the tops of one row is over the bulbs of another, but if the rain occurs, the bulbs should be brought to the curing house immediately

Late harvesting causes excessive sprouting during prolonged storage

Onion will produce 7-10 tons per ha


In the curing house they are cleaned, sorted, graded, packaged and stored 


Store in a clean, dry, cool and well-aerated place

Controlled atmosphere storage is practiced increasingly to extend the marketing period 

Well preserved onions can stay up to six months without getting spoilt; although it is advisable to use or sell them as early as possible as they will slowly lose weight


Post-harvest handling
Leave the bulbs in the field for 2-3 days before curing. Curing is one of the post-harvest handling techniques. 


Cleaning is done by removing the soil, foreign matter and badly affected onions manually or by using air

Curing process of drying the necks and leaves of the bulb to ensure maximum quality and increased shelf-life

Cure naturally sun-drying in the field or artificially

Artificial curing is better because of better process control. Spread the onions on a wire rack in a well-ventilated and shaded area. Put a covering on top of the onions to prevent them from rain

The onions are considered well-dried once the neck is tight the outer skin is dry, makes a rustling sound when handled and the skin colour is uniform. This takes 2 to 3 weeks

Sort to remove the onions with thick necks, the bolted, injured, decayed onions, doubles, small bulbs, bruised, damaged by pests, diseases and sun-scald and sprouted

Trim the onion roots and leaves using a sharp knife and cut 4-6 cm from the bulb

Grade according to colour and size as follows; Grade 1: Big sized onions, Grade 2: Small sized onions and Grade 3: Bulb-lets

Store in a clean, dry, cool and well-aerated place. Controlled atmosphere storage is practiced increasingly to extend the marketing period

Well preserved onions can stay up to six months without getting spoilt; although it is advisable to use or sell them as early as possible as they will slowly lose weight


Market as soon as possible to avoid losses in storage due to sprouting, rotting and contamination 


Onions stored in net bags

Package in net bags or crates that allow air movement through the onions

nion buyers include; local traders, brokers, cooperative societies, households, hotels and institutions, and food processing companies