Onion crops are mature and ready to be harvested when at least half of the tops have fallen over and begun to dry (Jauron, 2009). Mature onions should be harvested before heavy rain or prolonged periods of moisture. Rain on mature onions encourages the development of rot-causing fungi and bacteria while complicating manual and mechanical harvesting practices. For these reasons, harvest should be done as quickly as possible in dry climatic conditions to avoid poor weather and to prevent damage to onions (Matson, 1985). Damage to soil can occur if heavy tractor and truck traffic associated with harvest practices takes place on wet soil.
In Eastern Oregon, onion harvest typically occurs in late August and continues through early October when temperatures are usually warm and stable (Mansour, Mack, & Hay, 1979). Onions can be harvested either manually or mechanically. In manual harvesting for home gardens, the ground is loosened around the onion bulbs using forked tools and bulb tops are pulled from the ground (Opara, 2003). In the mechanized method, growers employ tractors and specialized machines to harvest their crops. Field toppers, windrowers, and crop lifters are machines commonly used to assist growers. Field toppers slice the tops off of onions, removing unwanted foliage and weeds by moving debris away from the crop bed. Windrowers lift onions from their beds and push them into a row so that crop lifters may move onions into a trailer for transport (“Mechanized Onion Harvest,” n.d.). Typically, growers use the windrowing technique 1 - 2 weeks before onions are sent to storage facilities. Once onions have been windrowed, they are cured by drying in the field.
Many growers rely on Top Air products to facilitate efficient onion harvest. This company (based out of Parma, Idaho) manufactures only onion and garlic harvesting equipment, but is best known for its all-in-one topper-loader machine that uses a ‘one-step’ process-- allowing growers to lift, top, remove debris, and load onions simultaneously, eliminating the need for extra processes and equipment (“Top Air - Onion and Garlic Farm Equipment | Mechanical Harvesting Technology,” n.d.). Other manufacturers may provide comparable equipment to facilitate more efficient harvesting practices.