1,530.6
kg/ha
—
seeds/m²
1,530.6
kg/ha
—
seeds/m²
The Seed Rate Calculator determines the amount of seed needed per hectare to achieve a target plant population, accounting for germination rate and seed purity. Correct seed rate is fundamental to crop establishment: too few seeds result in poor crop density and yield loss, while too many seeds waste seed and can cause excessive plant competition. This calculator is essential for farmers, agronomists, and seed companies.
Enter your desired plant population, the thousand seed weight (from seed testing), germination percentage, and seed purity percentage to get the recommended sowing rate in kg/ha and seeds per square meter.
The calculator uses the standard agronomic seed rate formula:
Seed Rate (kg/ha) = (Target Plants/m² x Thousand Seed Weight (g) x 10) / (Germination % x Purity % / 100)
Where the factor of 10 converts the units to kg/ha. The denominator accounts for the proportion of seeds that are both pure (not inert matter or other species) and capable of germination. Seeds per m² is calculated as:
Seeds/m² = Target Plants/m² / (Germination x Purity / 10000)
Inputs
Results
To achieve 300 plants/m² with 45g TKW seed at 90% germination and 98% purity, sow about 153 kg/ha (340 seeds/m²).
Inputs
Results
Canola with small seeds (4g TKW) targeting 60 plants/m² requires only about 2.9 kg/ha.
Thousand seed weight (TSW or TKW) is the weight in grams of 1,000 seeds. It varies by crop, variety, and season. You can determine it by counting 1,000 seeds (or 100 seeds and multiplying by 10) and weighing them. Alternatively, seed testing laboratories and variety descriptions provide this data. Common values: wheat 35-55g, barley 40-55g, canola 3-6g, maize 250-400g.
Not all seeds in a bag will produce plants. Germination rate indicates what percentage of pure seeds will actually sprout. Purity indicates what percentage of the seed lot is actually crop seed (versus weed seeds, inert matter, or other species). The effective seed rate must account for both factors, otherwise you will underestimate the amount of seed needed.
Optimal plant population varies by crop and environment. Too few plants leave gaps that are exploited by weeds and fail to utilize available resources. Too many plants cause intense competition for light, water, and nutrients, leading to thin stems, lodging, and disease. The target plant population should be based on local agronomic recommendations for the specific crop, variety, and growing conditions.
Roboculator Team
The Roboculator Team explains calculations, planning tools, and practical formulas in clear language for real-life situations.
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