Introduction
Oilseed sunflower is quickly gaining popularity as a feedstock crop for biodiesel because it shares several positive agronomic features with other common oil crops such as canola and soy; yields well in a variety of conditions, and can be grown easily and profitably at both small farm and large field scales. The high oil content of sunflower seed, often over 40%, makes it an excellent choice for a biofuel crop. Because it is already grown widely for use as food oil, agronomic practices are well established for regions where the sunflower is common in field rotations. Although pests can present production problems, careful rotations can help reduce inputs from fertilizer to pesticides.
Current Potential for Use as Biofuel
Sunflower oil holds great potential for offsetting petroleum diesel use, especially at the farm scale. Sunflower oils are already used for high-grade food oils, and the meal can be readily used as a livestock feed. Oil composition is similar to that of other vegetable oils such as soy and safflower, and biodiesel from sunflower is expected to have properties similar to biodiesel from soy.
Most sunflower oil is produced for human consumption, a high-value oil that nets a premium for producers. The value of sunflower for biodiesel end-use may not provide adequate economic returns in some oil-producing regions.
Biology and Adaptation
Sunflower grows in a variety of soil conditions but performs best in well-drained soils with high water-holding capacity. In drier regions it often needs at least supplemental irrigation for best yields. However, sunflower is considered a drought tolerant crop and has a deeper root system than most crops.
Sunflower is commonly considered a long season crop. It’s planted in mid- to late spring and matures between early September and early October, depending on exact planting date, variety, and growing degree day (GDD) accumulation. However, many hybrids have been developed that shorten the maturity period to less than 90 days, allowing harvest as early as late September.
Because wild sunflower is native to most regions of North America, the conditions necessary for growing cultivated sunflower exist widely, although best agronomic practices have not been well established outside of the Midwest, the High Plains, and Western Canada.
Production
Pay attention to yield, oil percentage, maturity, and pest resistance when selecting a hybrid. Consult variety trial results from nearby universities and/or commercial seed companies, or conduct on-farm variety trials.
For proper establishment, sunflowers prefer a fine seedbed. However, no-till production systems have been successful. Most regions suggest planting sunflower between early May and mid-June. Similar to corn, sunflowers require a soil temperature of 50 degrees F. to germinate.
A range of plant populations and row spacing work for sunflower production. With organic methods, 20- to 30-inch row spacing aids mechanical weed control. Recommended seeding rate for oilseed sunflowers ranges from 15,000 to 25,000 plants to the acre, with lower seeding rates in areas of low rainfall. A variety of sunflower-specific modifications are available for many seed metering systems, such as shorter finger-pickups and different cell plates.
Pest Management
Sunflowers are susceptible to a variety of pests, so management should include crop rotation, resistant cultivars, modified cultural practices, and often chemical control. Like other oilseeds, sunflower is susceptible to sclerotinia diseases and downy mildew. Carefully planned rotations are the most important element in disease management, as well as wider row spacing to increase air circulation, and resistant varieties.
For insect management, regular field scouting is essential. Some sunflower pests also infest other crops regularly used in rotations, including wireworms, long-horned beetles, and pale-stripped flea beetles. Plan rotations to disrupt lifecycles of these pests.
Harvest before the end of September to reduce huge losses to flocks of migrating birds. Control methods such as chemical deterrents, decoy crops, and harassment with explosions, gunshots, airplanes, and “squawkers” have had varying success. Best effects come from random but frequent changes in deterrent methods. The best management is to avoid nesting habitat.
Sunflower does not compete well with weeds early in its development. Use herbicide-tolerant hybrids (Clearfield and Express Sun), along with pre-plant or pre-emergence use of herbicide to control weed pressure before sunflower crops become well established. A number of herbicides are registered for sunflowers. However, in the Northeast, cultivating with a tineweeder one and two weeks after planting has controlled weeds as effectively as herbicide, although cultivating does cause small declines in standing sunflower population.
Harvest and Storage
Harvest is usually in late September to October, ideally once the seed has reached close to 12% moisture. Combining the plants earlier at high moisture contents (up to 25%) can reduce losses from seed shattering and birds, but wetter seed requires subsequent drying. Desiccants can hasten seed drying in the field, but must be applied after the plant reaches maturity.
Sunflower should be stored at around 9% moisture – at 10 or 11% the seed becomes more susceptible to insect and mold infestation, and oil extraction can become more difficult below 7%. Maintaining good seed condition is important for good oil content and quality. Air drying below 110 degrees F. is best for sunflower seed because fine hairs on the hull can ignite if they circulate through the drying fan and heat source, and in turn ignite the seed, which burns easily due to its high oil content.
Maintaining seed quality for use as a feedstock provides the largest challenge post-harvest. Heating over 200 degrees F. (e.g., during the drying process) degrades oil quality by increasing the concentration of free fatty acids, which must be removed in the beginning stages of the biodiesel production process. Over-drying the seed reduces the efficiency of oil extraction if processed by a mechanical seed press. Drying seed quickly after harvest and maintaining the seed at good storage moisture is important for keeping high seed and oil quality.
Potential Yields
Dryland sunflower yields generally average 1,300 pounds/acre, but yields over 2,000 pounds/acre in irrigated or high rainfall conditions are not uncommon. Average oil content is 40 to 42%. Oil yield extracted from the sunflower seed ranges from 35 to 80 gallons per acre. The quantity of oil extracted from the seed varies depending on growing conditions, post-harvest seed handling, and whether the oil was extracted through chemical or mechanical methods.
Summary
Sunflowers are a strong component of oilseed and biofuel cropping systems, because they adapt well to a variety of conditions and often require fewer agricultural inputs than more common crops. Because the oil has several potential markets and the pressed meal can fill niche cattle-feed markets, sunflower is a good choice for growers on both small and large scales.
