It´s the state flower of Kansas and plenty of them are grown in the western part of the state, but a Kansas State University agronomist is encouraging agricultural producers in another part of the state to give sunflowers a try.
Sunflowers can fit well into a rotation with wheat and other summer annual crops in south central Kansas, said K-State Research and Extension crops and soils specialist Stu Duncan. The development of new weed control technologies coupled with attractive commodity prices have sparked renewed interest in sunflower production.
Early May to early June planting dates are recommended for south central Kansas, said Duncan, who is based in northeast Kansas.
Duncan, who gave a presentation on sunflower production at the K-State Agronomy Field Day Aug. 22, referred to data from studies in the mid-late 1990s at K-State´s South Central Experiment Field near Hutchinson and the Harvey County Experiment Field near Hesston.
"It is important that soil moisture and temperature are adequate to produce uniform stands. May planting enhances the opportunity for greater seed yields and oil percentages vs. mid-June or later planting," he said.
Early planting is not without risk from sunflower head moth and stem weevil damage, however.
"Head moth has long been a challenge for Kansas growers, and the old adage of planting in mid-June or later to avoid moth flights and treatment is no longer valid," Duncan said. The increased use of no-till farming practices has resulted in increased stem weevil damage in the past decade as well. Successful sunflower production can be enhanced with timely and effective scouting and treatment for both of these pests if necessary.
Targeted final plant stands for dryland sunflowers are similar to those recommended for dryland corn, the agronomist said. The target at the South Central Experiment Field is 22,000 plants per acre, which should produce heads of 5 to 6 inches in diameter.
"This allows for a quick, uniform drydown in the fall, which leads to a timely harvest. Sunflowers are effective compensators and will increase head size if final populations are decreased. Larger heads often lead to delayed drydown, maturity, and harvest, with increased potential for losses to birds and plant lodging," he said.
According to Duncan, sunflowers develop deep roots and effectively explore the soil (up to seven feet deep) for water and nutrients. Their strong taproot can penetrate deeply in loamy, well-drained soils. Hard pans or plow/tillage layers in heavier soils are not as easily broken up or penetrated as is often claimed, he added.
About five-and-a-half inches of available soil moisture plus precipitation is needed to bring sunflowers to the point of producing seed, Duncan said. Yields will increase about 150 pounds per acre for every effective inch of water after that point, he added. To produce 1,000 pounds of seed per acre will require approximately 50 pounds of nitrogen, 15 pounds of phosphorus, and 35 pounds of potassium.
Early- to mid-May planting in south central Kansas with a 100-day hybrid usually lends itself to an early September harvest, allowing for ample time to recharge soil moisture from late summer and fall rains, he said.
More information about growing sunflowers is available at county and district K-State Research and Extension offices in the High Plains Sunflower Production Handbook, MF2384 and on the World Wide Web at http://www.oznet.ksu.edu/library/crpsl2/MF2384.pdf.