- Malheur Experiment Station
When planting onions, a grower must consider a number of things, such as which onion varieties to use (e.g. long-day onions in the Pacific Northwest) and when to plant them.
There are three different ways that onions can be planted: by sets, transplants, or direct seeding. Sets are grown from seeds and produce small bulbs, and then become dormant. The planting of sets and transplants can be beneficial because onions are ready to harvest one to two months earlier than onions planted by direct seeding (Shock et al., 2011).
The cost of planting in sets and transplanting is much higher than direct seeding. Because harvests can be completed earlier in the year when using transplants or sets, higher profits may be gained if there is better market demand for the produce. Planting sets or transplants require special equipment for the planting process. The cost of acquiring the necessary equipment should be considered. In some environments, the use of sets and transplants exposes the onion to a shorter duration of environmental pressures and reduces the need for weed and pest control. Equipment necessary for direct seeding includes a precision seed drill and other onion handling equipment. Monosem, which is known for its accuracy, Beck, which is inexpensive and covers the seed very well, and other planters can be obtained from South Georgia Equipment (Harvesting/ Field & Shed). Beck planters include a drive wheel, seed plates, variable spacers, and a shoe opener, which created grooves in the ground for the seeds to be dropped into. Vacuum planters use a sucking power to lift individual seeds and drop them into the soil in a very time-efficient and precise way. Milton Precision Planters can also be used; they are known for being able to cut through more trash than other planters (Milton Precision Planters). A mono-air planter plots seeds precisely using a metering unit (Precision Air Planters). Precise planters allow economic use of valuable seed. The equipment cited here provide examples and are not intended to be endorsements or criticisms of equipment not mentioned.
In the Pacific Northwest, a great majority of onion growers practice direct seeding. It is much easier and more cost-efficient to employ this method than the use of sets or transplants. While the harvest for this method is later in the year, onion prices fluctuate so it is often difficult to predict what harvesting time would be most beneficial.
Careful soil preparation is required with direct seeding because the earth must be tilled, smooth, and level to receive seeds. The ideal soil site is well-drained with nearly neutral soil pH (around 6.6-6.8) (Growing Onions). With direct seeding, every seed must be the same depth below the soil surface in order to germinate and grow uniformly. Usually, the seeds are planted around 1 inch deep.