Growing onion outdoors –if done rationally and on a scalable basis- can be a good source of income since onion is a high-demand vegetable worldwide. However, it can be quite a challenging and labor-intensive crop, and the farmer needs to follow some ground rules to obtain high yields and superior quality. In a few words, onion is a biennial or perennial plant, but growers cultivate it as an annual.
Understanding Onion Growth Requirements
The plant has specific requirements of photoperiod and temperature to form bulbs. Although it is a frost-tolerant plant, most varieties require average temperatures from 13 to 25°C (55.4 to 77°F) to form commercially accepted bulbs.
- Temperature Sensitivity: Extremely high temperatures during the bulb growth period will inhibit bulb development, making it nearly impossible for shocked plants to recover and give an acceptable yield.
- Sunlight Exposure: Every onion needs over 12 hours of sunlight exposure daily to develop well-shaped sets.
- Temperature Ranges: Plants need exposure to temperatures lower than 10°C (50°F) during the bulb-forming period, while temperatures should be close to 20°C (68°F) during the bulb-growing stage. Low temperatures during this stage may cause ill-formed onions, while high temperatures and drought may delay bulb formation.
Primary Uses of Onions
Onions are grown for three primary purposes:
- Production of Dry Bulbs
- Production of Sets
- Production of Seeds
Starting an Onion Crop: Propagation and Planting Methods for Onlion
To start an onion crop, the farmer has three options based on the propagation material:
- Seeds
- Sets
- Seedlings or Transplants
A grower can use onion seeds, sets, or seedlings-transplants. However, most commercial onion growers prefer sets or seeds for starting. Before they plant their onion sets, they prepare the field. They till and plow the land until it is finely grounded; in many cases, they make raised beds or furrows. They place a black plastic film through the rows in extremely cold weather conditions. The black plastic film helps the soil become warmer and controls weeds. They also establish the drip irrigation system or the sprinklers. Furrow irrigation is also applied but not suggested. When they are ready for planting, they either spread the seeds on the field or make small holes where they plant them manually or mechanically, in the case of sets and seedlings. Many growers apply for a suitable irrigation and fertilization program to obtain higher yields. Additionally, it is vital to use weed management practices since onions can suffer under weed pressure, especially during the first 10 weeks of their growth.
Harvesting and Post-Harvest Handling
The time from Planting to Harvesting depends on the growing method, the onion variety, the market target (bulbs or fresh onions), and climate conditions. Most commercial onion varieties grown for dry bulbs can be harvested 4-5 months after planting. In contrast, fresh onions need only a couple of months (providing both cultivations have started from sets, not seeds). Harvesting can be performed by hand or by harvesters. After harvesting, bulbs need to dry out (cured). Growers either leave them in the field to dry out or transfer them to special drying areas under controlled temperature and humidity conditions. The crop residues can be removed from the field, and the farmer applies crop rotation to control diseases and prevent soil from depleting.
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