Onion — Package of Practices
A bulb crop that lives or dies on drainage, sulphur and timing — keep it weed-free early, never waterlogged, and cure it well and it stores for months.
Overview
Onion is a cool-season bulb crop grown from transplanted seedlings (or sets). It is a heavy feeder, very sensitive to waterlogging, and slow to cover the ground — so weed control early and steady, even moisture are decisive.
Sulphur is the nutrient that sets onion apart: it builds pungency and storage quality. Curing the bulbs properly after harvest is what lets them keep for months.
Climate & season
Onion bulbs best in cool to mild weather (about 13–24 °C) during growth, with warmer, drier weather as bulbs mature. Day length and temperature together trigger bulbing, so choose a type suited to your latitude and season.
- Cool weather for leaf growth, warmer and drier for bulbing and maturity.
- Wrong day-length or excess nitrogen can cause bolting or thick necks.
- Wet weather at maturity invites neck rot and storage losses.
Soil & land preparation
A well-drained, fertile loam high in organic matter suits onion, at a pH of 6–7. Waterlogging is fatal.
- Plough to a fine, level tilth and ensure excellent drainage.
- Incorporate 25 t/ha of farmyard manure with biofertilizers.
- Form flat beds or broad ridges sized for easy, even irrigation.
- Rotate away from onion/garlic land to avoid basal rot and wilt.
Choosing a type & seed
Choose by season and day-length response (short-day for the plains), bulb colour and shape, and storage quality. Use fresh, true seed each season for good germination. No specific cultivar is named here.
Seed rate
- Transplanted crop: about 8–10 kg/ha of seed (raise a nursery).
- Small/aggregatum onion is planted from bulblets instead of seed.
Seed treatment
- Treat seed with Trichoderma viride or Thiram (≈ 4 g/kg) against basal rot and damping-off.
- Raise the nursery on raised beds with good drainage.
Nursery, transplanting & spacing
- Raise a nursery on raised beds; thin to avoid overcrowding.
- Transplant at 6–7 weeks, trimming long tops, into moist beds.
- Spacing: about 15 × 10 cm (rows 15 cm, plants 10 cm).
- Keep the field weed-free early — onion competes poorly with weeds.
Nutrient management
Onion is a heavy feeder that also needs sulphur — sulphur builds pungency and storage life. A common recommendation is N–P–K 100 : 50 : 50 kg/ha plus about 50 kg/ha of sulphur, on top of farmyard manure. Fine-tune to your soil test.
Apply as basal (at planting)
- Farmyard manure 25 t/ha with Azospirillum and Phosphobacteria (≈ 5 kg/ha each).
- Half the nitrogen and the full phosphorus, potassium and sulphur as the basal dose.
- Add zinc or boron only if a soil test or symptoms show a need.
Top-dress nitrogen
- Remaining half of the nitrogen in two splits, at about 30 and 45 days after transplanting.
- Finish all nitrogen before bulbs start to swell.
Irrigation
- Irrigate at transplanting, again after 3–5 days, then every 7–10 days.
- Keep moisture even — swings cause splitting and doubles.
- Onion is very sensitive to waterlogging; drain excess water fast.
- Stop irrigation 10–15 days before harvest so bulbs cure and store well.
Weeds & special care
- Keep the crop weed-free for the first 45–60 days — this is critical.
- Use a pre-emergence herbicide (e.g. pendimethalin) plus 2–3 hand weedings.
- Avoid deep hoeing near the shallow bulbs.
- Mulch helps hold moisture and suppress weeds.
Plant protection
Work the IPM way — clean seed, traps, weekly scouting and need-based sprays. Thrips and the leaf-blight diseases are the main targets in onion.
Major pests
| Pest | Damage | Manage with |
|---|---|---|
| Thrips | Rasp leaves, leaving silvery streaks; stunt bulbs | Blue sticky traps, neem, conserve predators; need-based spinosad use sparingly |
| Onion maggot | Larvae bore into the base and bulb | Clean cultivation, well-rotted manure only, crop rotation |
| Mites | Bronzing of leaves in hot, dry weather | Maintain moisture, recommended miticide if severe |
Major diseases
| Disease | Signs | Manage with |
|---|---|---|
| Purple blotch (Alternaria) | Purplish leaf spots with rings; leaves die back | Rotation, mancozeb sprays from ~20 days, a sticker in the spray |
| Stemphylium blight | Pale-to-brown spots merging on leaves | Same as purple blotch; good airflow, balanced nutrition |
| Basal rot (Fusarium) | Roots and base rot; plants yellow and topple | Treated seed/sets, rotation, Trichoderma in soil |
| Downy mildew | Pale patches with downy growth in cool, damp weather | Good drainage and airflow, recommended fungicide |
| Neck rot in store | Soft, grey rot at the neck during storage | Cure bulbs well, store cool, dry and ventilated |
Use chemicals safely
The products above are examples, not a prescription. Doses, approved crops and pre-harvest intervals differ by country and change over time. Always read the label, wear protective gear, use the correct dose, observe the waiting period before harvest, protect bees, and confirm with your local agriculture officer.
Harvest & yield
- Bulbs are ready when about half to three-quarters of the tops fall over and necks soften.
- Lift on a dry day; let bulbs dry in the field for a short while.
- Do not delay — over-mature bulbs sprout and store poorly.
- Typical yield: 25–35 t/ha under good management.
Post-harvest handling
- Cure the bulbs (with tops) in shade with good airflow for 1–2 weeks.
- Trim the tops and roots after curing; remove damaged or thick-necked bulbs.
- Store cool, dry and well-ventilated; avoid damp, which causes rot and sprouting.
- Grade by size for better market price.
Field tips that pay off
- Drainage and even moisture decide the crop — onion hates wet feet.
- Don't skip sulphur — it builds pungency and storage life.
- Weed early and hard; onion gives ground to weeds easily.
- Stop watering before harvest and cure well for months of storage.
Related crops
Onion — Package of Practices
A bulb crop that lives or dies on drainage, sulphur and timing — keep it weed-free early, never waterlogged, and cure it well and it stores for months.
Overview
Onion is a cool-season bulb crop grown from transplanted seedlings (or sets). It is a heavy feeder, very sensitive to waterlogging, and slow to cover the ground — so weed control early and steady, even moisture are decisive.
Sulphur is the nutrient that sets onion apart: it builds pungency and storage quality. Curing the bulbs properly after harvest is what lets them keep for months.
Climate & season
Onion bulbs best in cool to mild weather (about 13–24 °C) during growth, with warmer, drier weather as bulbs mature. Day length and temperature together trigger bulbing, so choose a type suited to your latitude and season.
- Cool weather for leaf growth, warmer and drier for bulbing and maturity.
- Wrong day-length or excess nitrogen can cause bolting or thick necks.
- Wet weather at maturity invites neck rot and storage losses.
Soil & land preparation
A well-drained, fertile loam high in organic matter suits onion, at a pH of 6–7. Waterlogging is fatal.
- Plough to a fine, level tilth and ensure excellent drainage.
- Incorporate 25 t/ha of farmyard manure with biofertilizers.
- Form flat beds or broad ridges sized for easy, even irrigation.
- Rotate away from onion/garlic land to avoid basal rot and wilt.
Choosing a type & seed
Choose by season and day-length response (short-day for the plains), bulb colour and shape, and storage quality. Use fresh, true seed each season for good germination. No specific cultivar is named here.
Seed rate
- Transplanted crop: about 8–10 kg/ha of seed (raise a nursery).
- Small/aggregatum onion is planted from bulblets instead of seed.
Seed treatment
- Treat seed with Trichoderma viride or Thiram (≈ 4 g/kg) against basal rot and damping-off.
- Raise the nursery on raised beds with good drainage.
Nursery, transplanting & spacing
- Raise a nursery on raised beds; thin to avoid overcrowding.
- Transplant at 6–7 weeks, trimming long tops, into moist beds.
- Spacing: about 15 × 10 cm (rows 15 cm, plants 10 cm).
- Keep the field weed-free early — onion competes poorly with weeds.
Nutrient management
Onion is a heavy feeder that also needs sulphur — sulphur builds pungency and storage life. A common recommendation is N–P–K 100 : 50 : 50 kg/ha plus about 50 kg/ha of sulphur, on top of farmyard manure. Fine-tune to your soil test.
Apply as basal (at planting)
- Farmyard manure 25 t/ha with Azospirillum and Phosphobacteria (≈ 5 kg/ha each).
- Half the nitrogen and the full phosphorus, potassium and sulphur as the basal dose.
- Add zinc or boron only if a soil test or symptoms show a need.
Top-dress nitrogen
- Remaining half of the nitrogen in two splits, at about 30 and 45 days after transplanting.
- Finish all nitrogen before bulbs start to swell.
Irrigation
- Irrigate at transplanting, again after 3–5 days, then every 7–10 days.
- Keep moisture even — swings cause splitting and doubles.
- Onion is very sensitive to waterlogging; drain excess water fast.
- Stop irrigation 10–15 days before harvest so bulbs cure and store well.
Weeds & special care
- Keep the crop weed-free for the first 45–60 days — this is critical.
- Use a pre-emergence herbicide (e.g. pendimethalin) plus 2–3 hand weedings.
- Avoid deep hoeing near the shallow bulbs.
- Mulch helps hold moisture and suppress weeds.
Plant protection
Work the IPM way — clean seed, traps, weekly scouting and need-based sprays. Thrips and the leaf-blight diseases are the main targets in onion.
Major pests
| Pest | Damage | Manage with |
|---|---|---|
| Thrips | Rasp leaves, leaving silvery streaks; stunt bulbs | Blue sticky traps, neem, conserve predators; need-based spinosad use sparingly |
| Onion maggot | Larvae bore into the base and bulb | Clean cultivation, well-rotted manure only, crop rotation |
| Mites | Bronzing of leaves in hot, dry weather | Maintain moisture, recommended miticide if severe |
Major diseases
| Disease | Signs | Manage with |
|---|---|---|
| Purple blotch (Alternaria) | Purplish leaf spots with rings; leaves die back | Rotation, mancozeb sprays from ~20 days, a sticker in the spray |
| Stemphylium blight | Pale-to-brown spots merging on leaves | Same as purple blotch; good airflow, balanced nutrition |
| Basal rot (Fusarium) | Roots and base rot; plants yellow and topple | Treated seed/sets, rotation, Trichoderma in soil |
| Downy mildew | Pale patches with downy growth in cool, damp weather | Good drainage and airflow, recommended fungicide |
| Neck rot in store | Soft, grey rot at the neck during storage | Cure bulbs well, store cool, dry and ventilated |
Use chemicals safely
The products above are examples, not a prescription. Doses, approved crops and pre-harvest intervals differ by country and change over time. Always read the label, wear protective gear, use the correct dose, observe the waiting period before harvest, protect bees, and confirm with your local agriculture officer.
Harvest & yield
- Bulbs are ready when about half to three-quarters of the tops fall over and necks soften.
- Lift on a dry day; let bulbs dry in the field for a short while.
- Do not delay — over-mature bulbs sprout and store poorly.
- Typical yield: 25–35 t/ha under good management.
Post-harvest handling
- Cure the bulbs (with tops) in shade with good airflow for 1–2 weeks.
- Trim the tops and roots after curing; remove damaged or thick-necked bulbs.
- Store cool, dry and well-ventilated; avoid damp, which causes rot and sprouting.
- Grade by size for better market price.
Field tips that pay off
- Drainage and even moisture decide the crop — onion hates wet feet.
- Don't skip sulphur — it builds pungency and storage life.
- Weed early and hard; onion gives ground to weeds easily.
- Stop watering before harvest and cure well for months of storage.