.calc-header {
text-align: center;
margin-bottom: 30px;
}
.calc-header h2 {
color: #2c5e2e;
margin: 0;
font-size: 28px;
}
.calc-header p {
color: #666;
margin-top: 5px;
}
.input-grid {
display: grid;
grid-template-columns: 1fr 1fr;
gap: 20px;
}
@media (max-width: 600px) {
.input-grid {
grid-template-columns: 1fr;
}
}
.form-group {
margin-bottom: 15px;
}
.form-group label {
display: block;
margin-bottom: 5px;
font-weight: 600;
color: #333;
}
.form-group input {
width: 100%;
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
box-sizing: border-box;
font-size: 16px;
}
.form-group .hint {
font-size: 12px;
color: #777;
margin-top: 2px;
}
.calc-btn {
width: 100%;
padding: 15px;
background-color: #2c5e2e;
color: white;
border: none;
border-radius: 4px;
font-size: 18px;
font-weight: bold;
cursor: pointer;
margin-top: 20px;
transition: background-color 0.3s;
}
.calc-btn:hover {
background-color: #1e421f;
}
.result-box {
margin-top: 30px;
padding: 20px;
background-color: #e8f5e9;
border-left: 5px solid #2c5e2e;
border-radius: 4px;
display: none;
}
.result-row {
display: flex;
justify-content: space-between;
align-items: center;
padding: 10px 0;
border-bottom: 1px solid #c8e6c9;
}
.result-row:last-child {
border-bottom: none;
}
.result-label {
font-weight: 600;
color: #2c5e2e;
}
.result-value {
font-weight: bold;
font-size: 20px;
color: #1b1b1b;
}
.article-section {
margin-top: 50px;
line-height: 1.6;
color: #333;
}
.article-section h3 {
color: #2c5e2e;
margin-top: 30px;
}
.article-section ul {
padding-left: 20px;
}
.article-section li {
margin-bottom: 10px;
}
function calculateSeedRate() {
// Get inputs
var targetPop = parseFloat(document.getElementById('targetPop').value);
var seedsPerLb = parseFloat(document.getElementById('seedsPerLb').value);
var germRate = parseFloat(document.getElementById('germRate').value);
var emergenceRate = parseFloat(document.getElementById('emergenceRate').value);
var totalAcres = parseFloat(document.getElementById('totalAcres').value);
var bagWeight = parseFloat(document.getElementById('bagWeight').value);
// Validation
if (isNaN(targetPop) || isNaN(seedsPerLb) || isNaN(germRate) || isNaN(emergenceRate) || isNaN(totalAcres)) {
alert("Please fill in all required fields with valid numbers.");
return;
}
if (germRate <= 0 || emergenceRate <= 0 || seedsPerLb 0) {
totalBags = totalLbsNeeded / bagWeight;
bagText = Math.ceil(totalBags) + " bags (" + totalBags.toFixed(1) + ")";
}
// Update DOM
document.getElementById('resLbsPerAcre').innerText = lbsPerAcre.toFixed(2) + " lbs";
document.getElementById('resSeedsPerAcre').innerText = Math.round(requiredSeedsPerAcre).toLocaleString();
document.getElementById('resTotalLbs').innerText = Math.round(totalLbsNeeded).toLocaleString() + " lbs";
document.getElementById('resTotalBags').innerText = bagText;
document.getElementById('resPLS').innerText = (survivalFactor * 100).toFixed(1) + "%";
// Show results
document.getElementById('results').style.display = 'block';
}
Understanding Seed Application Rates
Calculating the correct seed application rate is fundamental to achieving maximum crop yield and optimizing input costs.
Simply planting based on weight (e.g., "50 lbs per acre") without accounting for seed size, germination rates, and field conditions
can lead to stands that are either too thin (reducing yield potential) or too dense (increasing competition and disease risk).
Why Calculate Based on Target Population?
Seed sizes vary significantly between varieties and even within the same lot. For example, soybeans can range from 2,200 to 3,500 seeds per pound.
If you plant strictly by weight, you might be planting 30% more or fewer seeds than intended. This calculator starts with your
Target Population—the actual number of plants you want growing in the field—and works backward to determine the weight needed.
Key Variables Explained
- Target Population: The ideal number of plants per acre for your specific crop, soil type, and region.
- Seed Size (Seeds/lb): Found on the seed tag. Smaller seeds mean more seeds per pound, requiring fewer pounds per acre to hit the same population count.
- Germination Rate: The percentage of seeds that will sprout under ideal laboratory conditions.
- Field Emergence/Survival: A realistic estimate of how many seeds will survive actual field conditions (crusting, cold soil, pests). This is usually lower than the germination rate.
The Math Behind the Calculation
To determine the application rate, the calculator uses the following logic:
Required Seeds/Acre = Target Population ÷ (Germination % × Emergence %)
Lbs/Acre = Required Seeds/Acre ÷ Seeds per Pound
Frequently Asked Questions
What happens if I overestimate my emergence rate?
If you assume 95% emergence but field conditions only allow for 80%, your final stand count will be lower than your target, potentially reducing yield. It is often safer to be conservative with emergence estimates, especially when planting early in cool, wet soils.
How do I calculate seeds per pound?
This information is almost always printed on the seed bag tag. If you are using bin-run seed, weigh a small sample (e.g., 1 ounce), count the seeds, and multiply to find the count per pound.
Does row spacing affect the seeding rate calculation?
While row spacing affects how the planter is calibrated (seeds per linear foot), it does not change the total pounds required per acre for a broadcast or general density calculation. However, knowing the total seeds per acre allows you to calibrate planter transmission settings effectively.