Green onions can be marketed in late spring to lengthen the onion season.
Market Outlook. The per capita consumption of fresh onions increased from
nearly 15 ...
COOPERATIVE EXTENSION SERVICE UNIVERSITY OF KENTUCKY COLLEGE OF AGRICULTURE, FOOD AND ENVIRONMENT
Center for Crop Diversification Crop Profile
Onions
Cheryl Kaiser1 and Matt Ernst2 Introduction
Onions (Allium cepa) are a cool-season biennial crop typically grown as an annual. Dry bulb onions are harvested after the leaves have died back and the bulbs have fully matured. Green bunching onions are harvested while the leaves are still green and before the bulbs have developed. The terms ‘scallion’ and ‘spring onion’ are sometimes incorrectly used interchangeably for green onions. Scallions are onions that completely lack bulb formation, while spring onions have bulbs somewhat more developed than green onions.
Marketing
Fresh market options for Kentucky-grown onions include wholesale markets, farmers markets, community supported agriculture (CSA) shares, restaurants, and roadside stands. Sales to local retail markets, such as supermarkets, are also an option. Green onions can be marketed in late spring to lengthen the onion season.
Market Outlook
The per capita consumption of fresh onions increased from nearly 15 pounds in 1989 to 18½ pounds in 1999. According to the USDA, fresh onion use peaked at about 22 pounds in 2004, with per capita use in 2011 at more than 21 pounds. While increases in the 1990s were due in part to a greater demand for sweet onions, the more pungent storage varieties continue to dominate the market. 1 2
Production Considerations
Site selection and planting A site located in full sun with well-drained soil is essential for good onion production. Onions prefer a soil high in organic matter with a soil pH between 6.0 and 6.8. Onions can be grown from seeds, sets, or transplants. Most producers rely on either transplants or sets for commercial planting. An onion set is a small, dormant bulb that will produce a larger bulb once it is planted. Onion transplants are started from seed in a greenhouse or in ground beds approximately twelve weeks prior to planting in the field. Green bunching onions are grown from sets planted by mid-March, while bulb onions are commonly started from transplants. Depending on plant spacing, 50,000 to 120,000 onions are planted per acre. Because
Cheryl Kaiser is a former Extension Associate with the Center for Crop Diversification. Matt Ernst is an independent contractor with the Department of Agricultural Economics. Agriculture & Natural Resources • Family & Consumer Sciences • 4-H/Youth Development • Community & Economic Development
onions have poorly developed root systems, plants will require supplemental moisture via irrigation. Critical periods for irrigation are transplant establishment and bulb expansion.
Because onions have shallow root systems, cultivation is best used for weed management prior to bulb formation; once bulbing begins, hand weeding may be necessary.
Cultivars Onion cultivars are classified as either long-day, short-day, or intermediate day types, depending on the daylength required to initiate bulb formation. Intermediate types perform well at Kentucky’s latitude.
Harvest and storage Green onions are pulled and put into bunches when they are ⅓ to 1 inch in diameter.
Bulbs vary in color (red, yellow, and white), shape (round or flattened), and flavor (sweet or pungent). Many fresh market consumers are looking for sweet onions similar to the popular Vidalia onions. The short-day varieties that are often grown in the Vidalia region of Georgia are not suitable for production in Kentucky as they will bulb prematurely in the spring. However, other sweet, mild varieties bred specifically for fresh consumption can be grown in Kentucky. The right combination of cultivar and environment is important in production of these mild onions. For example, lower amounts of sulfur in the soil tend to produce milder onions than those grown in soils with high sulfur content. Pungent cultivars generally store better than sweet types. Pest management Disease problems include bulb and neck rots, leaf blast, and purple leaf blotch. Onion maggot and thrips are the main insect pests of onions. Growing resistant varieties, rotating crops, and following good cultural practices can help prevent many of these disease and insect problems; however, pesticide sprays may be needed in most years. Regular scouting of fields can help determine when and how often pesticides should be applied. Season-long weed management is essential since onions do not compete well with other vegetation and will not shade out the competition. Avoid planting onion into fields where noxious perennial weeds have a history of being difficult to control. Be sure the selected field is well prepared and weed-free prior to planting. Some annual and perennial weeds can be managed with herbicides.
Bulb onions are harvested when 70 percent of the plant tops have fallen. These onions are undercut, hand-pulled, and placed in windrows for field drying if weather permits. If rainy weather is a problem, onions are pulled after the tops have dried down, tops and roots are clipped off, and then bulbs are placed in shallow trays inside for drying. Onions are cured at high temperatures prior to storing in a well-ventilated area. Larger farming operations may place harvested bulbs in large bins to undergo forcedair curing for 1 to 3 days. Labor requirements Onions are planted and harvested by hand. Rutgers Cooperative Extension estimates labor needs of 184 hours per acre for planting, harvest, and packing of organically grown yellow onions.
Economic Considerations
The cost of transplants plus the hand labor for planting and harvest makes the initial investment for onion production high in comparison to some other vegetable crops. Additional costs include land preparation and the installation of an irrigation system. Production costs (2012) for onions (overhead irrigated) are estimated at $4,450 per acre, with harvest and marketing costs at $1,560 per acre. Total expenses per acre, including both variable and fixed, would come to approximately $6,010. Presuming yields of 50,000 pounds per acre and gross returns of $6,500 per acre ($13 per 100 pounds), returns to land, capital, and management would be approximately $490 per acre. Costs and returns can change drastically depending on the market.
Selected Resources
• Vegetable Production Guide for Commercial Growers, ID-36 (University of Kentucky) http:// www.ca.uky.edu/agc/pubs/id/id36/id36.htm • Green Onion Estimated Costs and Returns (Clemson, 2009) http://Cherokee.agecon.clemson.edu/onion6.pdf • National Onion Association http://www.onions-usa.org • Oklahoma Candy Onion Production: Projected Net Income, Price Risk and Yield Risk (Oklahoma State University, 2004) 3.3 MB file http://pods.dasnr.okstate.edu/docushare/dsweb/ Get/Document-968/p-1005web.pdf • Onion Production Guide, B-1198-2 (University of Georgia, 2007, Reviewed 2014) 5 MB file http://www.caes.uga.edu/Publications/ pubDetail.cfm?pk_id=7749&pg=np&ct=onion& kt=&kid=&pid
• Onions: the Sweet Smell of Success (USDA, 1998) http://webarchives.cdlib.org/sw1rf5mh0k/http:// www.ers.usda.gov/publications/agoutlook/ oct1998/ao255b.pdf • Organic Allium Production (ATTRA, 2006) http://attra.ncat.org/attra-pub/summaries/ summary.php?pub=25 • Weed Control in Bulb Crops (Onion, Leek, Garlic, Shallot) (University of Florida, 2010) http://edis.ifas.ufl.edu/wg033
Reviewed by Tim Coolong, Extension Specialist (Revised 2013) Photos by Tim Coolong, University of Kentucky (onion field) and Howard F. Schwartz, Colorado State June 2013 University, Bugwood.org (onion bulb) For additional information, contact your local County Extension agent Educational programs of the Kentucky Cooperative Extension Service serve all people regardless of race, color, age, sex, religion, disability, or national origin.
