How the calculation works
Baseline target density comes from tables for 4 regions (Dry Steppe 38–45 k/ha, Northern Steppe 45–55, Forest-Steppe 55–65, Polissia 60–70). A maturity multiplier adjusts: early hybrids tolerate +5% density, late hybrids need −5%. Seeding rate = target density / field germination × 1000. Seed units = rate / 150,000 (1 unit = 150k seeds).
- 1
Region
Sets the baseline density range by water availability.
- 2
Maturity group
Early, mid-early, or mid-late.
- 3
Sowing parameters
Area, row spacing (70 cm standard), field germination.
- 4
Read the result
Density, seeding rate, seeds per meter, purchase units.
When to use this tool
- Spring sunflower hybrid procurement planning
- Planter calibration before heading to the field
- Cross-checking regional recommendations
- Validating the agronomist's calculations
Limitations
The calculator does not account for: specific planter model, soil condition, sowing depth, preceding crop, or re-sowing probability. Clearfield hybrids can go 3–5% lower due to reduced weed pressure.
Frequently asked questions
Why is optimal density lower in the Steppe than Polissia?
In the dry Steppe, lower density reduces water competition between plants and increases thousand-seed weight. Polissia has enough water for denser plantings to pay off in yield per hectare.
What is field germination and why does it matter?
Field germination is the fraction of sown seeds that emerge. Standard is 85–95% depending on seedbed quality, moisture, and depth. Lower germination demands a higher seeding rate to reach target density.
How many seed units do I need for 100 ha?
For Forest-Steppe at typical parameters (60k/ha, 90% germination), you need ~44 seed units (1 unit = 150k seeds) per 100 ha. For Steppe: 30–35 units. For Polissia: 47–50 units.