Agronomy

Sunflower is an annual plant that is native to North America. It is known for being a very drought-and heat-tolerant crop and having a relatively short growing season, typically reaching maturity in approximately 100 days. Sunflower is predominately grown in the Great Plains states, such as Kansas, Colorado, South Dakota and North Dakota. Missouri is not a large sunflower producer. According to the USDA, Missouri produced 2.5 million pounds of sunflowers on approximately 2,000 acres during 2007.

Fitting Sunflowers into the Crop Rotation

Sunflowers can be planted as a full-season crop or as a double-crop after wheat. Farmers should use at least a three-year rotation before replanting sunflowers.

Site Selection

Like any crop, sunflower does best on medium-textured soils. It is more tolerant of “droughty” soils than most grain crops. Sunflower tolerates heavy clay soils, but these soils are not a good choice for bottom ground that stays wet.

Fertility

Nitrogen recommendations are 80 pounds to 100 pounds nitrogen per acre following non-legume crops and 60 pounds to 80 pounds nitrogen per acre following soybeans. Fertilize based on soil test recommendations for phosphorus and potassium replacement.

Variety Selection

Most major seed companies have commercial hybrid varieties available as oil-type or confectionary sunflowers. Oilseed hybrid varieties can be further broken down into linoleic, mid-oleic (NuSun) and high-oleic. Purchase oilseed rather than confectionary varieties. Herbicide-resistant Clearfield and ExpressSun varieties (non-GMO) are also available. Yields can vary significantly among sunflower varieties, and it pays to select good ones. Performance testing is a way for producers to select hybrids. Kansas Sunflower Trials have been conducted annually of sunflower hybrids in Kansas. The results can be a good source to evaluate when considering varieties.

Planting

Yields are similar for April through June planting, assuming adequate soil moisture. Farmers can plant until late July if needed. It is ideal to plant 20,000 plants per acre to 25,000 plants per acre, which is roughly 3 pounds to 4 pounds of seed per acre. Normally, plant in wide rows (30 inches to 38 inches) to provide space for the row header during harvest. Drilling sunflowers can be done, but this practice provides no yield advantage. Plant about 1 inch deep on heavy soils and 1.5 inch deep on sandy soils.

Weed Control

Weed control in the early stages of sunflower production is very important. Sunflowers are very competitive with weeds three or more weeks after sunflower emergence. Some herbicide options for weed control include:

• No-till planting: Apply a Spartan/Prowl tank mix or burndown with glyphosate prior to planting. Some Spartan formulations include glyphosate.
• Tillage: Apply a pre-plant-incorporated herbicide such as Treflan, Eptam or Sonalan, Dual Magnum or Spartan.
• Post-emergent weeds: Poast, Select and Assure are available for grass control. Beyond herbicide can be applied post-emergently for Clearfield varieties, and Express can be applied on ExpressSun varieties. Both Beyond and Express are ALS-inhibitor products that provide relatively broad-spectrum weed control.

Insects and Diseases

Several insects will feed on sunflowers, but to date, none have been an economic problem in the mid-South. Diseases have not been an issue in the mid-South, except in very wet, saturated soils. However, some diseases are a periodic problem in the Northern Plains. Scouting is recommended.

Harvest and Storage

When the back of the seed head turns brown, it is time to harvest. Desiccants can be used for an earlier harvest. Combine headers such as row crop, corn and small grain platforms can all be used to harvest sunflowers, though some modifications may be needed. A row crop head tends to be a good choice as it does not require modification. Operating at a lower ground speed can improve harvest efficiency.

Moisture control is important during storage. The moisture content should be at 10 percent or less if marketing within six months. Further moisture reduction should be used if storing for longer periods or during warmer months. Take precautions if drying beyond ambient air is anticipated.

For More Information

High Plains Sunflower Production Handbook (Kansas State)

Stages of Sunflower Development (North Dakota State)

Planting Supplement (National Sunflower Association)

Sunflower Insect Management (Kansas State)

Harvest Fundamentals (National Sunflower Association)

Drying and Storage of Sunflowers (National Sunflower Association)