Mortal Danger: Understanding Seedling Mortality
Written by Mitchell Japp, Research & Extension Manager, SaskBarley. This article on seedling mortality first appeared in the Spring 2022 edition of the BarleyBin Magazine.
Mortality is serious. On its own, it conjures images of the grim reaper — the black-hooded cloak and scythe, swooping in to complete its grim task. Seedling mortality seems less grim by comparison, but it is well worth understanding to ensure you get the most out of your barley.
Calculating seeding rates is designed to increase precision and accuracy — to ensure you’re planting to achieve the optimal plant stand for your farm. But, if you’ve calculated seeding rates before, you’ll know that it requires an estimate of seedling mortality. It’s hard to be precise or accurate with an estimate.
Seeding rate (lbs/ac) =
( Desired plant population / ft² ) Thousand Kernel Weight (g) ÷ ( Germination less seed mortality (in decimal form) ) ÷ 10.4
Read more about calculating seeding rates for malt barley.
Germination Minus Mortality = Seed Survivability
Germination minus mortality is equal to seed survivability.
In the seeding rate calculation, we have accurate values for TKW (weight of one thousand seeds in grams) and germination from the seed lab. But, we know that not all seeds that germinate will make it out of the ground and live. There are crop-specific estimates for seedling mortality, with cereals being among the best at 5–20 per cent. But, 5–20 per cent is a big range.
Why Seedling Mortality Varies
The challenge with seedling mortality is that it varies with management and environment. Management variability may come from:
- seed opener type
- row spacing
- seeding rate
- seeding speed
- seed-to-soil contact
- fertility management
- crop residue
- residual herbicide carryover
- and more…
With so many variables, there will be differences between farms, fields and years. But, taking the time to measure emergence will help to establish an appropriate baseline for your farm and take seeding rate calculations to the next level.
Step-by-Step: How to Measure Emergence
- Put a reminder in your phone or day planner to count emergence 21 days after planting. This is the optimal time to identify each plant before tillering starts and is long enough that all plants will be emerged.
- 21 days after seeding, count the emergence. Ideally, 6–10 locations that are representative of the field. The more uniform the field, the fewer locations are needed.
- Determine counts based on a square metre or square foot. You can use agronomic tools like a square foot or square metre, or count plants in a single row. To count plants in a single row, divide your row spacing into the area you are targeting. For example, for 12” row spacing, count the plants in 12” of row (144 in² ÷ 12 in = 12 in).
Defining the Terms: Mortality vs Survivability
Seedling mortality — or conversely, seed survivability or emergence percentage — may be used somewhat interchangeably in discussions of seeding rates. Seedling mortality describes the seeds we would expect to live but don’t, while seed survivability refers to what actually grows.
Calculating Seedling Mortality
See below the step to calculate seedling mortality (note: this will only work if the seeding rate used is based on a target plant stand and TKW):
- Note any observations about seeding conditions and management decisions that may affect seedling mortality.
- Using the average establishment from all locations, divide that into the target seeding rate. Subtract that amount from your germination and you’ll know the seedling mortality for that field.
For example, if you targeted 25 plants/ft² and you count 20 plants/ft², your emergence is 80 per cent and if the germination was 95 per cent, seedling mortality was 15 per cent.
Final Takeaway: Build Better Seeding Rate Estimates Over Time
Once you have collected seedling mortality for a few years, you’ll have a much more accurate and precise value to include in your seeding rate calculations. Taking good notes of the variability over time will also allow you to make adjustments to the calculation for specific conditions.
