Determining the seeding rate for winter wheat
Nebraska growers use seeding rates for winter wheat that vary from 30 to 180 lb per acre (320,000 to almost 3,000,000 seeds per acre). The lower rates are most common in drier areas. The higher rates are used for irrigated wheat which often is seeded in narrower rows and later in the season since it often follows another crop rather than fallow. This later seeding date reduces tillering and requires higher seeding rates to compensate for the reduction. Also, higher yield potential requires higher seeding rates.
Winter Wheat Seed Size Varies
Historically, wheat growers often calculated their seeding rate based on pounds of seed per acre; however, seed size varies and it's now recommended that growers calculate their seeding rate using seeds per acre to provide more accurate seeding results. The number of winter wheat seeds in one pound varies depending on the variety and the condition under which it was produced. In the 2014 Nebraska Winter Wheat Variety Evaluation for 14 trials, winter wheat yields ranged from a low of 24 to a high of 127 bushels per acre. Seed size ranged from a low of 10,700 seeds per pound to a high of 16,400 seeds per pound.
When weight is used for wheat seeding rates, a seed size difference of this magnitude can result in a 153% difference in seeding rate. With the good conditions for seed fill in 2014, there was less variation in seed size than in 2013 when the seed size in the variety test ranged from a low of 12,000 seeds per pound to a high of 23,000 seeds per pound, a 192% difference in seed size.
Winter wheat is capable of compensating among yield components, which often results in similar grain yields being produced across a fairly wide range of seeding rates. However, using seeding rates that are too low can lead to excessive tillering. It also may delay maturity, increase weed competition, and fail to make use of the plant's full yield potential. Using rates that are too high may increase costs, result in increased lodging, and possibly reduce yields.
Too much competition, even among small grain plants, may lead to fewer kernels per head and lower kernel weight. The key is to get an optimum plant population with uniform distribution for efficient use of available resources.
click image to zoom A review of seedling rates vs. yield potential is helpful. On average, there are 22 seeds per head and 5 heads per plant, or 110 seeds per plant. With an average seed size of 15,000 seeds per pound or 900,000 seeds per bushel, a pound of average-sized seed with 80% germination and emergence has a yield potential of approximately 1.5 bushels per acre. Seeding 40 lb of seed with a weight of 15,000 seed per pound has a yield potential of 60 bushels per acre.
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