Onion Farming

Lesson 1.1 — Why onions are the storage crop

• Every household, restaurant and street vendor uses onions daily — demand never stops, and unlike tomatoes the crop does not perish in days.
• The price curve: onions are cheapest at the harvest glut and typically 2–4× higher in the months before the next crop. Properly cured and stored onions turn time into money.
• Yields: neglected crops give 10–15 t/ha; well-managed irrigated crops give 30–50 t/ha. Bulb size and uniformity — both management outcomes — decide your price per kg on top of that.

Lesson 1.2 — Day-length: the make-or-break lesson

• Onion plants only start forming bulbs when daylight passes a variety-specific threshold. Categories: short-day (bulbing at about 10–12 hours — correct for most tropical/subtropical Africa), intermediate (12–14 h), long-day (14–16 h — temperate Europe/North America).
• Plant a long-day variety near the equator and the threshold is never reached: you grow beautiful leaves, no bulbs, and lose the season.
• Always confirm with your dealer/extension officer: "Is this variety short-day and recommended for our area?" Common short-day types in Africa include Texas Grano-family, Red Creole, Bombay Red and locally bred selections — availability varies by country, so ask locally rather than ordering blind.

Lesson 1.3 — Colour, pungency and the market

• Storage rule of thumb: the more pungent and firm the bulb, the longer it keeps. Mild sweet onions are for eating soon, not for the price curve.

Lesson 1.4 — Site, soil and rotation

• Onions want deep, loose, well-drained loam or sandy loam with high organic matter; pH 6.0–7.0. Heavy clay produces small misshapen bulbs and rots them in wet spells.
• Shallow roots (mostly in the top 20–25 cm) mean onions are poor competitors for water and nutrients and are HELPLESS against weeds — a fact that dictates Month 4.
• Rotate 3+ years away from onions, garlic, leeks (allium family) to escape purple blotch, downy mildew, white rot and nematodes. White rot in particular contaminates soil for a decade or more.
• Full sun, no shade, and a reliable irrigation source for 4–5 months.

Lesson 2.1 — The onion nursery

• Seed rate: 3–5 kg/ha of seed raised in nursery beds produces the 400,000+ seedlings a hectare needs. For 500 m², that's roughly 150–250 g.
• Nursery beds 1 m wide, raised 15 cm, with fine tilth and well-rotted compost; sow in shallow drills 10–15 cm apart, thinly, and cover lightly with fine soil then a thin grass mulch until emergence (remove it as seedlings appear).
• Water gently twice daily with a fine rose; shade lightly in the hottest weeks; onion seed germinates in 7–12 days and seedlings are slow and delicate for the first month.
• Onion seed loses viability fast — never use seed more than a year old unless you have tested germination.

Lesson 2.2 — Nursery care to transplant

• Keep the nursery meticulously weed-free — competing weeds at seedling stage cripple the crop before it starts.
• Damping-off is the main nursery killer: thin sowing, no waterlogging, good airflow, and clean media prevent it.
• Transplant at 6–8 weeks when seedlings are pencil-lead thick and 15–20 cm tall (about 3–4 leaves). Older, thicker seedlings are more likely to bolt (run to flower) later.
• Harden off 5–7 days: reduce watering and remove shade so seedlings toughen before the field.

Lesson 2.3 — Preparing the field

• Plough/dig deep and work to a FINE, level tilth — bulbs cannot swell properly in cloddy or compacted ground.
• Incorporate 20–30 t/ha of well-rotted compost or manure (never fresh manure — it causes thick necks, forked bulbs and rots in storage).
• Form raised beds 1–1.2 m wide where drainage is at all doubtful; onions hate wet feet and rot fast in standing water.
• Basal fertiliser: a phosphorus-rich compound at roughly 300–500 kg/ha worked into the bed before transplanting.

Lesson 2.4 — Alternative planting methods

• Direct seeding: cheaper on labour, needs precise sowing and excellent weed control; common on larger mechanised farms.
• Sets (small bulbs): fastest to harvest and easy, but expensive per hectare and prone to bolting — useful for small plots and early market.
• Transplanting (this course's track): best bulb uniformity and land-use efficiency for smallholders, since the field is only occupied for 3–3.5 months.

Lesson 3.1 — Transplanting technique

• Lift seedlings after watering the nursery; trim excessively long roots slightly and (optionally) tip the leaves by a third to reduce wilting.
• Plant SHALLOW — 2–3 cm deep only. Deep planting is a classic beginner error: it produces thick necks, small bulbs and poor storage.
• Firm the soil around each seedling and irrigate immediately; transplant in the cool of late afternoon.
• Gap-fill within 7–10 days from your spare seedlings.

Lesson 3.2 — Spacing and plant population

• The trade-off to understand: closer spacing = more total tonnage but smaller bulbs; wider spacing = fewer, larger bulbs. Let your MARKET decide — supermarkets and export want big uniform bulbs; local markets often prefer medium.

Lesson 3.3 — Irrigation: consistent, then decisive

• Onions need steady moisture in the top 20–25 cm — shallow roots mean frequent lighter irrigation (every 3–5 days depending on soil and weather), not occasional floods.
• Critical demand periods: establishment and the bulbing phase. Water stress during bulbing directly shrinks bulb size — this is where yield is won.
• Avoid overhead irrigation late in the day; wet foliage overnight invites purple blotch and downy mildew. Drip or furrow is far better for onions.
• STOP irrigation 2–3 weeks before harvest — this is a deliberate signal that hardens the bulb skins, tightens the necks and dramatically improves storage life. Onions irrigated up to lifting rot in the store.

Lesson 3.4 — Top dressing

• Nitrogen top dressing in 2 splits: about 3–4 weeks after transplanting and again at 6–8 weeks (roughly 100–150 kg/ha of AN/urea equivalent in total, adjusted to soil fertility).
• Stop all nitrogen once bulbing starts — late nitrogen produces soft, thick-necked bulbs that rot in storage and delays maturity.
• Potassium and sulphur matter for onions: sulphur drives pungency and storage quality; a sulphur-containing fertiliser is a real advantage where soils are deficient.

Lesson 4.1 — The weed war (onions' greatest weakness)

• Onions' thin upright leaves never shade the ground, so weeds grow unchecked and can cut yields by 50–80% — more than any pest or disease in this course.
• Keep the crop weed-free especially for the first 8–10 weeks: shallow hand-weeding every 2–3 weeks, never deep (onion roots sit in the top 20 cm and are easily cut).
• Weed labour is the biggest cost item in smallholder onion production — budget it honestly, or use mulch between rows and consider registered pre-emergence herbicides on larger areas with extension guidance.

Lesson 4.2 — Thrips: the main pest

• Onion thrips are tiny slender insects hiding in the leaf axils; damage shows as silvery-white streaks and stippling, then distorted, drying leaves — and heavy infestations cut bulb size sharply.
• They explode in hot dry weather. Scout weekly by pulling leaves apart and looking into the neck of 20 plants across the field.
• Management: overhead sprinkling (which physically knocks thrips down) where disease risk allows, blue sticky traps, registered insecticides ROTATED between chemical groups (thrips develop resistance notoriously fast), and neem-based products in low-input systems. Spray with high pressure into the leaf axils, or the chemical never reaches them.

Lesson 4.3 — Diseases

Lesson 4.4 — Bolting and doubling (quality problems)

• Bolting (flower stalk shooting up): caused by over-large seedlings, cold spells after transplanting, or stress. Bolted bulbs have a woody core and will not store — remove and sell them fresh immediately.
• Doubles/splits (two bulbs in one skin): caused by irregular watering and over-thick seedlings — even irrigation prevents most of it.
• Both problems are decided at nursery and transplant stage, not at harvest — which is why Month 2's seedling spec matters.

Lesson 5.1 — Knowing when to lift

• The signal: tops fall over (neck softens and leaves lodge) across the field. Harvest when about 50–80% of tops have fallen — not before, and not weeks after.
• Don't artificially bend tops over early: it's an old habit that reduces yield and storage quality; let the crop tell you.
• Lift in dry weather after the 2–3 week irrigation cut-off. Wet-lifted onions are storage failures waiting to happen.

Lesson 5.2 — Lifting technique

• Loosen with a fork and pull by hand; NEVER throw bulbs into piles or drop them into containers. Every bruise is a rot entry point that shows up six weeks later in the store.
• Leave bulbs in the field a day or two to dry if weather is dry and hot sun isn't scorching them — covering rows with the leaves of the next row protects bulbs from sunscald while they dry.
• Discard immediately: thick-necked bulbs, bolters, doubles, damaged or diseased bulbs. These are the SELL-NOW pile; they must never enter the store.

Lesson 5.3 — Curing (the single most important post-harvest step)

• Curing means drying the neck and outer skins until the neck is tight and papery — typically 2–3 weeks in shade with good airflow (or field-curing plus shed time in dry climates).
• Methods: spread bulbs in a single layer on slatted racks or dry ground under a ventilated shelter; or tie tops and hang bunches; or windrow in the field where weather is reliably dry.
• The test: a properly cured onion has a completely dry, tight neck that doesn't slide when twisted, papery outer skins, and a rustling sound when handled.
• Then top and trim: cut tops leaving 2–3 cm of dry neck (never cut into the bulb), trim roots close, and gently brush off loose soil — no washing, ever.

Lesson 5.4 — Grading

• Grade by size: small (under ~40 mm), medium (40–70 mm), large (70 mm+) — and separate any bulb with a soft neck, split skin or blemish.
• Uniformity is what buyers pay for: a graded 20 kg net of even medium reds beats a mixed sack every time, in every market.
• Record percentages by grade — this is your quality KPI and it improves measurably every season you apply this course.

Lesson 6.1 — Storage: turning time into money

• Ideal smallholder store: DRY, well-ventilated, shaded, off the ground. Onions store best cool and dry — in tropical conditions a raised slatted platform in a ventilated shed with cross-breeze is the practical standard.
• Never store in sealed plastic sacks — use net bags, slatted crates, or traditional hanging plaits/tied bunches under a roof. Air movement is everything.
• Stack shallow (no deep piles crushing lower bulbs) and inspect every 2 weeks: remove any softening bulb immediately — one rotting onion spoils the bag around it.
• Realistic storage life: 2–5 months for well-cured pungent varieties in good ventilated conditions; less in humid climates. Sprouting and softening signal it's time to sell.

Lesson 6.2 — Marketing on the curve

• Sell in tranches, not all at once: some at harvest (cash flow and reject clearing), some mid-curve, some at the peak. Trying to hit the exact top is gambling; laddering out is business.
• Channels: farm-gate traders (lowest, fastest), municipal markets, supermarkets and processors (graded, contracted), restaurants/vendors (regular medium volumes), and lean-season retail by the bucket (highest per kg).
• Keep a market notebook of weekly prices — after two seasons you'll know your local curve better than the traders quoting you.

Lesson 6.3 — The worked economics (1 hectare, irrigated)

• The levers, in order: weed control (labour), correct day-length variety, bulb uniformity/grading, curing quality, and selling tranche timing. Note that storage losses of 10–30% are normal — always compute the curve gain NET of shrinkage and rot.

Lesson 6.4 — Value addition

• Dried onion flakes and powder (see the rAs Solar Drying course) convert small, split and surplus bulbs into a shelf-stable, high-value product with no cold chain.
• Peeled/prepped onions for restaurants and pickled onions are further options where hygiene standards can be met.

Lesson 6.5 — Final project: your bankable business plan

• Assemble: variety choice with day-length justification, rotation history, nursery-to-harvest calendar, irrigation plan including the cut-off, weeding labour budget, thrips/disease programme, curing and storage design, grade percentages achieved, the price curve chart with your selling tranches, risk plan (bolting, thrips resistance, storage rot, price collapse), and a 3-season growth path.
• Submit with photos and records for your rAs certificate — onion plans with a storage strategy are exactly what input-credit and aggregator schemes look for.