Seed Rate Calculation Formula

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Seed Rate Calculator

Recommended Seeding Rate:
0.00
Pounds of Seed per Acre
function calculateSeedRate() { var targetPop = parseFloat(document.getElementById('targetPopulation').value); var seedsLb = parseFloat(document.getElementById('seedsPerLb').value); var germ = parseFloat(document.getElementById('germinationPercent').value) / 100; var purity = parseFloat(document.getElementById('purityPercent').value) / 100; var survival = parseFloat(document.getElementById('survivalPercent').value) / 100; if (targetPop > 0 && seedsLb > 0 && germ > 0 && purity > 0 && survival > 0) { // Formula: Seeding Rate (lb/acre) = (Target Pop) / (Seeds per lb * Germ % * Purity % * Survival %) var denominator = seedsLb * germ * purity * survival; var rate = targetPop / denominator; document.getElementById('seedResult').innerText = rate.toFixed(2); document.getElementById('resultBox').style.display = 'block'; } else { alert("Please enter valid positive numbers for all fields."); } }

How to Use the Seed Rate Calculation Formula

Calculating the correct seeding rate is essential for maximizing crop yield and optimizing your input costs. Sowing too little seed results in poor weed competition and reduced yields, while sowing too much leads to unnecessary costs and potential disease issues due to overcrowding.

The standard formula used in this calculator is:

Seeding Rate (lb/acre) = Target Population ÷ (Seeds per lb × Germination % × Purity % × Survival %)

Key Factors in the Calculation

  • Target Plant Population: This is the number of established plants you want per acre. This varies significantly by crop (e.g., soybeans vs. wheat) and row spacing.
  • Seeds per Pound: Seed size varies by variety and growing conditions. Check your seed tag for this specific number, as it significantly impacts the bulk weight needed.
  • Germination Rate: Found on the seed tag, this indicates the percentage of seeds expected to sprout under ideal conditions.
  • Seed Purity: This accounts for the percentage of actual crop seed versus weed seeds or inert matter (chaff/stems) in the bag.
  • Field Survival Rate: This is an estimate of how many germinated seeds will actually survive to become established plants. This depends on soil temperature, moisture, planting depth, and pest pressure. Common estimates range from 80% to 95%.

Practical Example

If you are planting Soybeans with a target of 140,000 plants per acre, using seed that has 2,800 seeds per pound, 90% germination, 99% purity, and you expect a 90% survival rate:

  • Math: 140,000 / (2,800 × 0.90 × 0.99 × 0.90)
  • Denominator: 2,800 × 0.8019 = 2,245.32
  • Result: 62.35 Pounds per Acre

Why Pure Live Seed (PLS) Matters

The combination of Germination and Purity is often referred to as Pure Live Seed (PLS). Calculating based on PLS ensures you are adjusting for the quality of the seed lot. For example, a bag of seed with low germination requires a higher bulk seeding rate to achieve the same plant stand as a high-quality lot.

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