Achieving the optimal plant stand is the foundation of a successful harvest in Alberta's unique growing conditions. This Seeding Rate Calculator helps producers determine the exact amount of seed required to meet target plant populations, moving away from the outdated "bushels per acre" approach to a more precise "seeds per square foot" methodology.
How the Calculation Works
The calculation is based on the standard formula used by Alberta Agriculture and Irrigation. It considers the physical weight of the seed (TKW) and the expected loss due to germination issues and field mortality.
*Note: The division by 10 is a conversion factor derived from converting square feet to acres and grams to pounds.
Input Variables Explained
Target Plant Density: The number of plants you want to establish per square foot. This varies by crop type and moisture conditions.
Thousand Kernel Weight (TKW): The weight of 1,000 seeds in grams. This is critical because seed size varies significantly between varieties and years. Large seeds require a higher seeding rate by weight to achieve the same plant count.
Germination Rate: The percentage of seeds that will sprout under ideal conditions (found on your seed tag or lab test).
Expected Emergence: The percentage of germinated seeds that actually survive field conditions (depth, crusting, insects, disease). Typical Alberta values range from 80% to 90% for cereals, but can be lower for pulses or canola.
Target Plant Densities for Alberta Crops
Use these general guidelines as a starting point for your inputs:
Crop Type
Target Density (plants/ft²)
Typical TKW (g)
Spring Wheat
25 – 35
30 – 45
Durum
25 – 35
40 – 50
Barley (Malt/Feed)
22 – 26
40 – 50
Oats
25 – 30
30 – 45
Canola
5 – 8
3 – 6
Field Peas
7 – 9
180 – 280
Why Precision Matters
Seeding too light can result in delayed maturity, uneven stands, and increased weed competition. Seeding too heavy increases seed costs and can lead to lodging or higher disease pressure. By adjusting for TKW and Emergence, you ensure that every acre gets exactly the potential it needs.
function calculateSeedingRate() {
// Get input elements
var targetDensityInput = document.getElementById("targetDensity");
var tkwInput = document.getElementById("tkw");
var germinationInput = document.getElementById("germination");
var emergenceInput = document.getElementById("emergence");
var resultDiv = document.getElementById("resultsArea");
var errorDiv = document.getElementById("errorMsg");
// Get values
var targetDensity = parseFloat(targetDensityInput.value);
var tkw = parseFloat(tkwInput.value);
var germination = parseFloat(germinationInput.value);
var emergence = parseFloat(emergenceInput.value);
// Clear previous error
errorDiv.style.display = "none";
errorDiv.innerHTML = "";
// Validation
if (isNaN(targetDensity) || isNaN(tkw) || isNaN(germination) || isNaN(emergence)) {
errorDiv.style.display = "block";
errorDiv.innerHTML = "Please fill in all fields with valid numbers.";
resultDiv.style.display = "none";
return;
}
if (targetDensity <= 0 || tkw <= 0 || germination <= 0 || emergence <= 0) {
errorDiv.style.display = "block";
errorDiv.innerHTML = "All values must be greater than zero.";
resultDiv.style.display = "none";
return;
}
// Calculation Logic
// 1. Calculate Total Survival Percentage (decimal format)
// Example: 95% germ * 85% emergence = 0.8075 survival rate
var totalSurvivalDecimal = (germination / 100) * (emergence / 100);
// 2. Exact Formula Calculation
// Seeds per acre = Target (plants/ft2) * 43,560 (ft2/acre) / Total Survival
var seedsPerAcre = (targetDensity * 43560) / totalSurvivalDecimal;
// Weight in grams per acre = (Seeds per acre / 1000) * TKW
var weightGramsPerAcre = (seedsPerAcre / 1000) * tkw;
// Weight in lbs per acre = Grams / 453.59237
var weightLbsPerAcre = weightGramsPerAcre / 453.59237;
// Metric Conversion: 1 lb/ac = 1.12085 kg/ha
var weightKgPerHa = weightLbsPerAcre * 1.12085;
// Display Results
document.getElementById("resImperial").innerHTML = weightLbsPerAcre.toFixed(1) + " lb/ac";
document.getElementById("resMetric").innerHTML = weightKgPerHa.toFixed(1) + " kg/ha";
document.getElementById("resSurvival").innerHTML = (totalSurvivalDecimal * 100).toFixed(1) + "%";
resultDiv.style.display = "block";
}
function resetCalculator() {
document.getElementById("targetDensity").value = "";
document.getElementById("tkw").value = "";
document.getElementById("germination").value = "";
document.getElementById("emergence").value = "";
document.getElementById("resultsArea").style.display = "none";
document.getElementById("errorMsg").style.display = "none";
}