You’ve chosen the variety or varieties you want to grow in 2016. You’ve decided on your target plant stand. And from your seed test results, you have the percent germination and thousand kernel weight (TKW). But have you given any thought to your seedling mortality?
When calculating the seeding rate needed to achieve your target plant stand, you often hear about TKW and percent germination. But remember when calculating seeding rates, you need to take into account the seedling mortality rate, i.e. what percent of viable seed will germinate but not produce a plant.
Seedling mortality can vary greatly from year to year, and field to field. For cereals, seedling mortality rates can range from 5 to 20%. Many farmers and agronomists have found a 5 to 10% mortality rate can be assumed. However, farmers may need to make adjustments to their seedling mortality based on factors such as available moisture, soil temperature, residue cover, seed quality, amount of seed-placed fertilizer, seeding depth, seeding date, and disease and insect pressure.
One additional factor you maybe should consider is the impact of seeding rate itself on seedling mortality or stand loss. Grant Mehring from North Dakota State University shared some recent work at the 2015 Manitoba Agronomists Conference looking at optimum seeding rates for hard red spring wheat. Across 23 environments from 2013 to 2015, his research showed increased stand loss as seeding rate increased (from a percent stand loss of 3% at the lowest seeding rate up to 21% at the highest seeding rate). His research suggests using a seedling mortality of 10 to 20%, even under good seed bed conditions.
Determining seedling mortality is not easy. Since mortality depends on the combination of conditions and management practices of individual farms, producers should keep records of emergence (and thus mortality) in their fields each year. The data collected will help in the future when calculating seeding rates.
Submitted by: Pam de Rocquigny, Provincial Cereal Crops Specialist, Manitoba Agriculture
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