Onion curing after rain: store, or sell the lot today?
Kailash Patidar of Pandhana, Khandwa, harvested 150 quintals of onion (mostly N-53, some Bhima Super) from 0.6 ha between 18 and 20 February. The bulbs were left in the field for only two days, and then 22 mm of unseasonal rain fell. About 40 per cent of the bulbs still have thick necks and 15 per cent show bruising from the hook while lifting. He plans to keep 100 quintals on a raised bamboo platform under a thatched shed he used last year, when he lost 28 per cent of weight and 18 per cent of bulbs to rot. The mandi price today is Rs 1,150 per quintal, and traders expect Rs 1,600 to Rs 1,700 in April. Cold storage 40 km away charges Rs 60 per quintal per month; his own shed costs about Rs 40 per quintal per month in handling and interest. A buyer offers Rs 1,200 per quintal for the whole lot today, cash.
1. Which part of the lot should go to storage, which should be sold now, and what curing must be done first?
Read the worked answer
Not all 150 quintals are storage material. Pretending otherwise is exactly what produced last year's 28 per cent weight loss.
Sell now
- All thick-necked bulbs (roughly 60 quintals). A thick neck never dries into a tight seal, so it is an open door for Botrytis and Aspergillus, and the bulb sprouts early because the growing point is still active.
- All bruised, cut or skinned bulbs (about 22 quintals); these rot first and infect the rest.
- Any bulb with a soft or watery neck, or with sunken spots.
Store only if
- The neck is fully dry and papery, 2-3 outer scales are intact, roots are clipped, and there is no soft spot.
Curing before storage
- Spread in a single layer under shade with free cross-ventilation for another 10-14 days, never in a heap.
- Top the neck to 1-1.5 cm, strip loose skins, and grade by size.
- Do not cure in direct sun; after rain, long sun exposure causes sunscald and doubles the rot.
Because 22 mm of rain fell after only two days of field curing, curing has effectively restarted from a wet skin, so the realistically storeable share is 55-65 quintals, not 100.
2. Work out whether storing 100 quintals on his own shed is better than selling today, and find the loss level at which storage just breaks even.
Read the worked answer
Sell today 100 q x Rs 1,200 = Rs 1,20,000, with no further cost.
Store for four months Storage cost = 100 q x Rs 40 x 4 = Rs 16,000.
- At 25 per cent loss: 75 q x Rs 1,650 = Rs 1,23,750. Less Rs 16,000 = Rs 1,07,750, about Rs 12,250 worse than selling today.
- At 15 per cent rot plus 10 per cent weight loss: 100 x 0.85 x 0.90 = 76.5 q x Rs 1,650 = Rs 1,26,225. Less Rs 16,000 = Rs 1,10,225. Still below today's offer.
Break-even Storage must gross Rs 1,20,000 + Rs 16,000 = Rs 1,36,000. At Rs 1,650 that is 82.4 q, meaning total loss must stay below about 17 per cent. His record last year was 28 per cent weight loss plus 18 per cent rot, far worse than that; the rain-damaged, thick-necked lot will certainly not beat 17 per cent.
Decision Take the buyer's Rs 1,200 per quintal for the thick-necked and bruised bulbs. Storing the best 40-50 quintals is a price speculation that only works if April price touches Rs 1,700 and losses stay under about 12 per cent - and that should be a deliberate gamble with a small, well-cured lot, not a default plan for 100 quintals.
3. If he does store 40-50 quintals, what management inside the shed will limit rot and sprouting without banned chemicals?
Read the worked answer
The store has to do three things: keep the bulbs dry, keep them cool, and keep air moving.
- Structure and loading. Bamboo platform at least 30-45 cm above the floor, thatched roof with a ridge vent, sides that can be opened for morning air, bulbs in layers 3-4 deep and never against the wall; leave 15-20 cm gaps between stacks.
- No mixing. Never put the new lot into old residues or old bulbs; clean the shed, remove last year's debris and disinfect the platform.
- Ventilation management. Open the sides in the morning and evening, close during hot afternoons and during rain or humid spells. High humidity inside is what drives both sprouting and neck rot.
- Sorting. Inspect every 2-3 weeks; remove and sell sprouted, soft or mouldy bulbs at once, because one rotting bulb infects its neighbours.
- No household chemicals. Do not dust with unknown powders, do not treat stored onions with insecticide, and do not use maleic hydrazide now - as a sprout suppressant it is a pre-harvest spray applied about two weeks before lifting, not a storage treatment.
- Sell in stages. Market the smallest bulbs first, since they lose proportionately more weight and have no price advantage in April.