Onion Yields - How much onions can yield per hectare/acre
Onion yields vary depending on planting season, growing methods, and environmental conditions. As for the yields, after years of practice, a good yield for dry onions is 35-50 tons per hectare (31.2-44.6 lb/acre) for spring planting, usually under irrigation. Some onion growers have mentioned that autumn planting gives greater yields of up to 60-90 tons per hectare. Some Utah farmers also report up to 110 tons per hectare (100,000 lb/acre).
When onions are cultivated as an intercrop with turmeric, sugarcane, or bananas, yields are more modest, averaging 5-9 tons per hectare (approximately 4461-8030 lbs/acre). For the production of onion sets, good yields generally fall between 20-30 tons per hectare (17844-26765 lbs/acre), while fresh green onions can yield around 19-25 tons per hectare (16951.4-22305 lb/acre) (keep in mind that green onions are harvested in multiple hand-harvesting).
When and How to Harvest and Cure Onions
The ideal onion harvest time depends largely on the intended use of the onions, whether for fresh green onions or dry bulbs.
- Preparing for Harvest: For dry onions, all fertilization should cease about 4-5 weeks before harvest, and irrigation should stop 3 weeks before to avoid any quality reduction and facilitate harvest.
- Green Onion Harvest: Fresh green onions are typically ready 2-3 months after planting once the leaves have reached a commercially desirable size but are still tender.
- Dry Onion Harvest: For dry onions, harvesting begins when over 50% of the plants have leaned over (ideally between 90-95%). Harvesting too early can result in smaller bulbs, outer leaf loss, or premature sprouting. On the contrary, leaving onions in the field for too long can expose them to frost or rainfall, making curing more challenging and increasing the risk of loss.
Some growers prefer to use special machines to trim the roots of the onions about 2.5-5 cm (1-2 in) below the bulb. This technique is usually applied when 60-70% of the plants’ tops have tipped over. After that, onions may remain on the field for another 10 days on the ground if the environmental conditions allow it. Generally, onions are harvested either by hand (higher costs and labor but better quality and fewer losses) or mechanically using harvesters. All onion bulbs must be cured before being stored or sold to prevent rot, maintain their good quality, and prolong their shelf-life. Curing can take 2-4 weeks and is usually continued after the harvest (out of the field) with the onion bulbs to be placed in bins in open windy sheds or by using forced air.
In most cases, producers cut the dry tips of the harvested onions (topping) 2-3 cm (0.8-1.2 in) above the bulb after harvesting and before storage. Some machines can also perform both topping and windrowing operations simultaneously. It is crucial to avoid cutting the tops when they are still fresh and green since there is a risk of neck rot in storage. The only case tips are not pruned is when onions are knitted into braids.
In the case of fresh green onions, they are harvested 2-3 months after planting when the leaves have achieved a commercial size but remain tender. All the plants are uprooted either manually or mechanically and transferred to rooms where they are cleaned and tied into groups of 4-5. Then, they are transferred directly to the market.
Storing and Packaging of Onions
After curing and topping, onion bulbs can be graded and placed in a storage (common or cold) facility.
- Dry Bulb Onions: Usually, onion bulbs are stored in bags, bulk bins, crates, pallets, or boxes. It is best to avoid placing the onions in piles larger than 3 meters (10 feet) deep because the base ones will be injured due to compression. For prolonged storage (up to 8 months), the farmers can place their product at 0 °C (32 °F) and 65-70% relative humidity. Conditions like a temperature between 4.5-10 °C (40-50 °F) and high relative humidity should be avoided when storing onion since they can accelerate the sprouting and decay of the bulbs.
- Fresh Green Onions: On the other hand, the fresh green onions should be stored at 0 °C (32 °F) and 95-100% relative humidity. However, this product has a much shorter shelf-life than dry bulb onion (7-10 days). Finally, it is essential to avoid any frost injuries (in the field or storage) that will decrease the quality and commercial value of the onions.
It is interesting to remember that the sweeter the onion, the more water it contains, which results in a shorter storage shelf-life. For the same reason, pungent onions can be stored better for longer.
Onions can be graded and sorted based on color, size, and quality before packaging. Bulb onions are packaged in 20-23 kg (44-50 lb) sacks (or net bags) or in smaller mesh bags (more appropriate for selling directly to consumers).
References
- https://archive.dpi.nsw.gov.au/__data/assets/pdf_file/0020/470027/Onion-hand-harvest-gross-margin-budget.pdf
- https://extension.usu.edu/vegetableguide/onion/harvest-handling
- https://aggie-horticulture.tamu.edu/archives/parsons/publications/onions/ONIONGRO.html
- https://ohioline.osu.edu/factsheet/hyg-1616
- https://nhb.gov.in/pdf/vegetable/onion/oni004.pdf
- https://content.ces.ncsu.edu/bulb-onions
- https://web.extension.illinois.edu/veggies/onion.cfm
- https://www.wifss.ucdavis.edu/wp-content/uploads/2016/10/GreenOnions_PDF.pdf
Further information
- Interesting Facts about Onions
- Onion: Info, Nutritional Value, and Health Benefits
- Onion Plant Information and Variety Selection
- How to Grow Onions At Home: Onion Growing Guide for Beginners
- Commercial Onion Farming - How to Grow Onions for Profit
- Onion Soil Requirements, Soil Preparation, and Planting
- Which Factors Can Affect Bulbing in Onions?
- Onion Water Requirements and Irrigation Systems
- Onion Nutrient Needs and Fertilization Requirements
- Major Onion Pests and Diseases and Sustainable Management Practices
- Onion Weed Management: How to Control Weeds in an Onion Field
- Onion Harvest, Yields, and Storage