Establishing Successful Stands
Sunflower stand establishment has been characterized as one of the most difficult aspects of production in some growing seasons. Reasons for poor stands are not always well understood. However, poor stands not only handicap yield and quality production potential, but can also increase weed competition.
Last year, Colorado State University area extension agronomist Ron Meyer conducted a preliminary investigation regarding some controllable factors that may affect sunflower stands. He looked at sunflower type (confection vs. oil), seed size (large vs. small), and planting depth (1, 2, and 4 inches deep).
A sunflower stand evaluation was planted on June 2, 2005 at the Northern Sun site located near Goodland, Kan. The previous crop was hard red winter wheat. Planted sunflower population was 19,000 plants per acre. Both an oil (Triumph 645) and confection (Triumph 757) type were evaluated.
Plots were planted in a north, south direction. Herbicide applied was Spartan at 1 oz/ac and Dual Magnum at 2 pt/ac. Weed control was excellent, season long. Planting unit was a John Deere planter with cone attachments for metering seed and with two 30-inch wide rows. The planter is equipped with adjustable depth bands that allow an accurate planting depth.
Soil insects that feed on sunflower seedlings were not a concern at this silt loam dryland site. Soil moisture conditions were excellent at planting with rainfall occurring both before and after planting. A rotary hoe operation was necessary 7 days after planting to address crusting concerns.
Within each type both a large and small seed size were planted at depths of 1, 2, and 4 inches below the soil surface (the exception was large seed oil and confection that were not planted at the 1 inch depth). In addition, treatment number 7 (small seed confection at the 4 inch depth) was not observable due to other factors. Seed sizes within each type were from the same lot.
The stand comparisons:
1. small seed oil type at 2 inch depth
2. small seed oil type at 4 inch depth
3. small seed oil type at 1 inch depth
4. large seed oil type at 2 inch depth
5. large seed oil type at 4 inch depth
6. small seed confection at 2 inch depth
7. small seed confection at 4 inch depth (trt. Lost)
8. small seed confection at 1 inch depth
9. large confection at 2 inch depth
10. large confection at 4 inch depth
Stand evaluation results
Statistical differences from sunflower stand counts were not found from the 1 and 2 inch planting depth across types, but were found reduced from the 4 inch planting depth. When analyzed across sunflower types, a 60% stand reduction was found from the 4 inch planting depth regardless of seed size and type – all 4 inch planting depths recorded lower stand counts.
When the sunflower stand data was analyzed by seed size across all planting depths and sunflower types, the small seed size was found to emerge better. Stand reductions of 39% were found from the large seed versus small seed across all types.
No statistical stand differences were found by sunflower type, which Meyer notes was an interesting observation, since it has been observed that confection stands are usually thinner than oil type in production fields when treated the same. However, it appears that when soil moisture conditions are near perfect, confection and oil stands may be similar.
Yet when all treatments were analyzed together, large confection seed size planted at the two inch depth did record noticeably smaller stand numbers and was the only 2 inch depth to be included in the stand reduction group. All other treatments that produced significantly low stands were planted at the 4 inch depth. Large confection seed size also recorded 46% stand reductions when compared to small confection seed size planted at the same 2 inch depth. In addition, all large seed confection treatments recorded significantly lower stands.
This may signal a trend that indicates larger confection sunflower seed size may struggle to emerge, regardless of depth, even in ideal conditions. Meyer cautions that more information is needed before generalizations can be made, however. A second year for this study is being planned in 2006, with changes being considered regarding statistical design in an effort to more clearly define treatment differences.
“My take on this from just one year of evaluation is that if soil moisture is depleted for dryland sunflower at planting, you have two options,” says Meyer. “You can wait for better moisture conditions so you can plant shallow and get a better stand, or if you’re forced to plant deep, plant a smaller seed size and increase the population. Those are the options I would consider if I was planting.” – Tracy Sayler
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