Wheat field Cody Creech
WHEAT WORK: Seeding rates and planting dates for winter wheat are being studied on this plot in McCook, Neb.

Rethinking winter wheat seeding rates

Extension Crop Connection: Planting by number of seeds per acre, not pounds per acre, may make more sense as practices, equipment and varieties change.

Historically, winter wheat was seeded based on pounds of seed per acre or bushels per acre. Although this method was easy to calculate and remember from year to year, changes in production practices and equipment, and greater diversity in varieties has given way to a new and better way of seeding winter wheat: using seeds per acre.

Nebraska wheat growers typically use seeding rates from 40 to 180 pounds per acre depending on the variety, location and row spacing. Lower rates are more common in drier, nonirrigated areas, and higher rates are more common in areas with more rainfall or irrigation.

Seed size can vary dramatically from variety to variety and year to year. Goodstreak, for example, has a small seed size, around 16,500 seeds per pound, whereas Wesley has a large seed size, around 11,000 seeds per pound.

A grower seeding Goodstreak using the pound-per-acre method would need to seed 45% more pounds than Wesley to achieve the same number of seeds per acre.

Year-to-year differences are common and largely depend on environmental conditions during seed fill. This is evident when comparing wheat in the state variety trial. Seed size ranged from 12,000 to 23,000 seeds per pound in 2013 compared with 10,700 to 16,400 seeds per pound in 2014, which had good conditions during seed fill.

Seed quality is also important and can influence emergence, vigor and tillering. Specifically, large, dense seeds are preferred over small, light seeds. This is one benefit of using seed that has been cleaned using a gravity table to remove light seed. Many certified seed dealers or custom seed cleaners use gravity tables to improve seed quality. Using bin-run seed that has not been properly cleaned may need a higher seeding rate to account for the lower-quality seed that is being seeded.

The amount of protein in the seed can also be used to differentiate seed quality.

Understand that this is not necessarily referring to the protein percentage, rather the total amount. For example, a small and large seed may both have 12% protein; however, the larger seed has a greater amount. High levels of protein in the seed increases seedling vigor and becomes of added importance when soil nitrogen is limited.

Study on seeding rates
For the past two years, a field study has been conducted across five locations in western Nebraska. This research is partially funded by the Nebraska Wheat Board to evaluate seeding rates and planting dates for winter wheat. Planting date recommendations have not been significantly changed since the early 1960s.

At the time this article was written, harvest is still underway in western Nebraska, and results from the year have not been evaluated. However, general observations from last year’s data and visual observations from this year will be used.

Winter wheat seeding recommendations for western Nebraska dryland winter wheat will likely be based on the number of seeds per foot of row. The current research is evaluating seeding rates on both 7.5- and 10-inch row spacings using seeding rates of 14, 16, 18 and 20 seeds per foot of row. Floyd E. Bolton at Oregon State University suggests 18 seeds per foot of row seems to be the point where significant yield increases begin to diminish.

Last year, 16 or 18 seeds per foot of row generally achieved the greatest yields across the locations evaluated. This held true for both the 7.5- and 10-inch row spacings. Almost as consistent was a yield decrease when seeding at 14 seeds per foot of row.

Late-seeded winter wheat has less time to get established prior to cold weather. This wheat will have fewer tillers and requires a greater seeding rate to compensate and maintain yields. As such, seeding rates should be adjusted according to seeding date, as well as available soil moisture. Inadequate moisture delays germination and emergence.

Wheat yields varied last year by as many as 20 bushels per acre for the same variety across planting dates and seeding rates. Tailoring seeding rates and avoiding late seeding dates will maximize yields for winter wheat growers. Ensuring a minimum of 16 to 18 seeds per foot of row is recommended based on the information interpreted thus far. More specific recommendations for seeding rates and planting dates will be developed as research results are analyzed.

Creech is a Nebraska Extension dryland cropping systems specialist.

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