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Seed Size, Planting Depth Can Impact Stands

Thursday, February 15, 2007
filed under: Optimizing Plant Development/Yields

Planting depth and seed size can have a clear impact on getting a sunflower stand off to a good start, according to observations in a second year of experiments at the Colorado State University/K-State Northern Sun research site near Goodland, Kan.

CSU area extension agronomist Ron Meyer looked at sunflower type (confection vs. oil), seed size (large vs. small), and planting depth (1, 2, and 4 inches deep) which is in the second research year

The dryland evaluation plot was planted no-till into winter wheat stubble on June 6, 2006. Seed drop was 17,000 plants per acre. Both an oil (Triumph 645) and confection (Triumph 757) type were evaluated, with same seed lots used between seed sizes. Soil moisture conditions were ideal. Germination was about 85%-90% for both types. Key observations include:

• Overall the oil type emerged better than the confection type.

• Both the oil and confection type emerged best from the shallow planting depths, and worst at the 4” planting depth. In fact, sunflower emergence from the 4” depth was about 50% that of the shallow planting depth for both the oil and confection type.

• The larger seed versus the smaller seed size from the oil type emerged similar with no statistical differences found. However, the smaller confection seed size emerged significantly better than the larger sized seed.

Results were similar to those in 2005, and Meyer plans a third year of testing this

summer. Meyer speculates that emergence might be more of a struggle for the larger, woody shell of the confection sunflower seed, especially so under dry soil conditions.

Meyer points out that while emergence at the 1” depth was good in both research years, this might be too shallow to recommend for planting. “These last two testing seasons have had ideal soil moisture at planting, which aided emergence from the shallow depth. However, if the weather gets hot and dry, that top 1” is the first to dry out, which will actually reduce the stand. If the third year bears the same data, we may promote a shallow planting depth possibly between 1 and 2 inches,” he says.

Sunflower growers who irrigate may need to prewater, so the soil profile has enough water to get the sunflower seedlings off to a good start. Dryland sunflower producers may want to wait for better moisture conditions if soil at planting is too dry. It’s generally recommended that sunflower be planted at a depth of 1.5 to 2.5”. If you’re planting at the furthest end of that range or deeper, consider planting a smaller seed size and increasing the planted population. – Tracy Sayler

Start Thinking Planter Calibration

The importance of a uniform plant stand is important for treatment timing during the growing season, including irrigation, weed and pest control, and desiccant application for dry-down. Planter calibration is part of the equation. If a planter isn’t calibrated correctly, or the wrong planter plate is used, and there can also be variances in per-pound seed count, seed shape, and seed type which can put plant populations off kilter, and result in uneven stands.

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