Harvesting and Handling of Onion

It's not good to leave the onions in the ground for longer than two weeks after the tops die because they become open to organisms that can cause rots in storage, or they might even start growing again. Pull your onions up on a sunny day if you can, then let them sit in the sun for another day or so to dry (in hot climates this usually takes just a few hours). This drying kills the root system at the bottom of each bulb. The roots will be like little brittle wires when they're dry. Picking the right day to pull the onions can determine how well the onions will keep. If you harvest them after some rainy weather they'll have a lot more moisture in them and won't dry out well.

  • Storage and Conditioning
  • Curing

Undercut or pull and windrow onions when at least 60% of tops have fallen down, and leave in windrow until inside neck tissues are dry before topping and storing. If the season is too damp for field curing, dry in storage at temperatures between 27 to 35 oC with relative humidity at 70% to 80% for 2 weeks or cure with forced ventilation at 27 to 35 oC. Curing with forced air at 35 oC can be complete in as little as 48 hours. Best skin colour develops when onions are cured at 24 to 32 oC with 80% relative humidity. Properly cured onions will have a tight neck and dry outer scales that rustle. Onions for setts are pulled and cured in late summer or early fall while the tops are still green, and when the bulbs reach 2 cm in diameter. Larger setts produce a high proportion of "bolters''.

  • Storage 

Following the curing period, onions should be cooled and held at 0 oC and 65% to 70% relative humidity. With forced air circulation, it may be possible to allow humidity as high as 85%. Root growth and decay are stimulated at high humidity, and sprouting occurs at high temperatures. Thick-necked onions will not keep and should be removed before storing if possible. Onions are frequently stored in bulk storage, two or four meters deep, constructed so that the bulbs can be cured by forcing air up through them. This method is considered more efficient and economical than curing and storing in crates. Properly cooled onions can be successfully stored at 0 oC for 6 to 8 months.

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