How the calculation works
Formula: sowing usability = (purity × germination) / 10,000. Rate in million seeds = target productive stems / usability. Rate in kg/ha = million seeds × thousand-seed weight. Target stem density is 4.2 M/ha in Steppe, 4.7 M/ha in Forest-Steppe, 5.2 M/ha in Polissia (compensating for higher losses on light soils).
- 1
Region
Sets the target productive stem density.
- 2
Thousand-seed weight
From the seed certificate (typically 35–50 g).
- 3
Lab germination and purity
From the certificate (typically 92–98% and 99–100%).
- 4
Area
Used for the total seed weight calculation.
When to use this tool
- Planning seed procurement for autumn sowing
- Verifying the sowing rate before planter calibration
- Adjusting for lower-germination seed lots
- Comparing varieties with different thousand-seed weights
Limitations
The calculator assumes 15 cm standard row spacing and drilled sowing. For broadcast, add 20–30% to the rate. It does not account for sowing date (late sowing needs higher rate), sowing depth, or specific variety.
Frequently asked questions
Why does Polissia need a higher rate than the Steppe?
Light sandy Polissia soils have lower field germination and higher winter losses (heaving, damping). Target productive stem density rises from 4.2 million in Steppe to 5.2 million in Polissia, which directly raises the sowing rate.
How does thousand-seed weight affect the rate in kg?
Directly proportional. A million seeds at 40 g/1000 weighs 40 kg; at 50 g/1000 it weighs 50 kg. Larger seed has higher emergence vigor but costs more and requires more kg per hectare.
What is sowing usability?
The product of purity and germination, divided by 10,000. Example: 99% purity × 95% germination / 10,000 = 0.9405. The target productive stem count is divided by this to get the real sowing rate, accounting for non-viable seeds.