According to Larry Kleingartner, former executive director of the National Sunflower Association, common strategies agronomists and farmers have for working with late-planted sunflower include:
•Switch to an early maturing hybrid.
•Open or blacken the soil to warm it up for quicker emergence.
•Plant shallow, but into moisture, for faster emergence.
•Reduce some of the inputs to lower crop production costs.
•Plant slightly higher populations for quicker drydown.
•Minimize use of "stay green" hybrids to escape late-season drydown issues.
•Minimize use of "plant health" fungicides to avoid late-season drydown issues.
•Consider using a desiccant to aid drydown if it can be applied in time to be effective.
South Dakota and southern North Dakota farmers can plant sunflowers through early July. More-northerly locations commonly look at June 15 to June 20 as a last planting date, Kleingartner says.
The NDSU Carrington Research and Extension Center conducted a four-year date of planting study that used June 20 as the final planting date. The June 20 date in that central North Dakota location experienced a 25% yield reduction compared to a May 20 planting date, averaged across the four years.
The scenario is similar in South Dakota. Kathleen Grady, SDSU sunflower breeder, conducted a three-year date of planting study at multiple sites in that state's north and south crop insurance zones. Average yield (all locations) on a June 25 planting date in the north zone was 1,375 pounds per acre — 25% lower than the June 10 planting yield. The June 30 planting date in the southern zone yielded 1,350 pounds per acre on average — 32% lower than the June 15 planting date.
Yields for both of the South Dakota late-planting dates were still higher than the county average T-yields. Test weight and oil content declined with the later plantings, while harvest moisture increased.
"The key question is: Does a potential 25% yield reduction, compared to peak yield, still generate sufficient revenue compared to the risk of filing for prevent plant and leaving that land idle?" Kleingartner says.