Optional: Calculates total seed needed for the job.
Calculated Seed Rate:0 kg/ha
Actual Establishment:0%
Total Seed Required:0 kg
Seeds Per Hectare:0 million
Optimizing Yield with Accurate Seed Rate Calculations
In modern agronomy, the "spray and pray" method of sowing crops is obsolete. Calculating the precise seed rate is one of the most cost-effective ways to maximize crop yield potential while managing input costs. Whether you are planting wheat, barley, canola, or soybeans, understanding the relationship between Thousand Seed Weight (TSW), germination rates, and field conditions is critical.
Why Not Just Plant by Weight?
Planting a fixed weight (e.g., 100 kg/ha) without considering seed size can lead to disastrous variation in plant populations. Seed size varies significantly between varieties and growing seasons.
For example, if you plant 100 kg/ha of large seeds (TSW 50g) versus small seeds (TSW 35g), the smaller seeds will result in 43% more plants per square meter. This overcrowding creates competition for moisture and nutrients, leading to weak stems and lodging. Conversely, under-seeding leads to weed proliferation and lower yield caps.
Key Formula Components
Target Plant Density (Plants/m²): The optimum population for your specific crop and region. For winter wheat, this might be 200-300 plants/m²; for spring barley, perhaps 225-275 plants/m².
Thousand Seed Weight (TSW): The weight in grams of 1,000 seeds. This is the most variable factor and should be measured for every new batch of seed.
Germination %: The viability of the seed under ideal lab conditions. High-quality certified seed usually exceeds 95%.
Emergence % (Field Loss): This accounts for seeds that germinate but fail to break the soil surface due to depth, crusting, pests, or cold. A typical clay loam soil might have 85-90% emergence, while harsh conditions could drop this to 60-70%.
The Math Behind the Calculator
The standard agronomic formula used in this tool is:
By dividing by the product of germination and emergence (often called the "Establishment %"), we ensure that enough extra seeds are planted to account for the inevitable losses, guaranteeing you hit your target stand count.
function calculateSeedRate() {
// Get input values
var density = parseFloat(document.getElementById('targetDensity').value);
var tsw = parseFloat(document.getElementById('tsw').value);
var germination = parseFloat(document.getElementById('germination').value);
var emergence = parseFloat(document.getElementById('emergence').value);
var area = parseFloat(document.getElementById('fieldArea').value);
// Validation logic
if (isNaN(density) || isNaN(tsw) || isNaN(germination) || isNaN(emergence)) {
alert("Please fill in all required fields (Density, TSW, Germination, Emergence) with valid numbers.");
return;
}
if (germination <= 0 || emergence 0) {
totalSeedKg = seedRateKgHa * area;
}
// Step 6: Seeds per hectare (for reference)
var seedsPerHaMillions = (seedsPerSqM * 10000) / 1000000;
// Display Results
document.getElementById('results').style.display = 'block';
document.getElementById('resRate').innerHTML = seedRateKgHa.toFixed(2) + " kg/ha";
document.getElementById('resEstablishment').innerHTML = (establishmentFactor * 100).toFixed(1) + "%";
if (totalSeedKg > 0) {
document.getElementById('resTotal').innerHTML = totalSeedKg.toLocaleString('en-US', {minimumFractionDigits: 1, maximumFractionDigits: 1}) + " kg";
} else {
document.getElementById('resTotal').innerHTML = "-";
}
document.getElementById('resCount').innerHTML = seedsPerHaMillions.toFixed(2) + " million";
}