*Survival rates typically range from 85% to 95% depending on soil conditions and equipment.
function calculateLentilRate() {
var target = parseFloat(document.getElementById('targetPop').value);
var tkw = parseFloat(document.getElementById('tkw').value);
var germ = parseFloat(document.getElementById('germination').value);
var surv = parseFloat(document.getElementById('survival').value);
if (target > 0 && tkw > 0 && germ > 0 && surv > 0) {
// Formula: Seeding Rate (kg/ha) = (Target Population x TKW) / (Germination % x Survival % / 100)
// More accurately: (Target * TKW) / ( (Germ/100) * (Surv/100) * 100 )? No.
// Standard Ag Formula: Rate (kg/ha) = (Target Plants/m2 * TKW in grams) / (Expected Survival %)
// Where Survival % is the decimal product of Germination and Seedling Survival.
var decimalSurvival = (germ / 100) * (surv / 100);
var kgHa = (target * tkw) / (decimalSurvival * 100);
var lbAc = kgHa * 0.892179;
var buAc = lbAc / 60; // Standard 60lb bushel for lentils
document.getElementById('kgHaResult').innerHTML = kgHa.toFixed(2) + " kg/ha";
document.getElementById('lbAcResult').innerHTML = lbAc.toFixed(2) + " lb/ac";
document.getElementById('buAcResult').innerHTML = buAc.toFixed(2) + " bu/ac";
document.getElementById('lentilResults').style.display = 'block';
} else {
alert("Please enter valid positive numbers for all fields.");
}
}
Optimizing Your Lentil Seeding Rate
Determining the correct seeding rate for lentils is critical for maximizing yield and managing weed competition. Unlike some other crops, lentils do not "branch out" as aggressively to fill gaps, making the initial plant population vital to your harvest success.
Factors Influencing the Calculation
Target Plant Population: For most lentil varieties, the recommended target is 120 to 130 plants per square meter (approx. 11-12 plants per square foot). Large green lentils may perform better at slightly lower densities (around 110 plants/m²).
Thousand Kernel Weight (TKW): This varies significantly by variety and seed lot. Small red lentils may have a TKW of 30g, while large green lentils can exceed 70g. Always check your seed tag.
Germination Rate: This is the percentage of seeds expected to sprout under ideal conditions, provided by your seed lab report.
Survival Rate: This accounts for "field mortality." Factors like seed-placed fertilizer, soil temperature, seeding depth, and pathogens typically result in a 5% to 15% loss of viable seeds.
Common Lentil Variety TKW Reference
Lentil Class
Typical TKW Range (grams)
Small Red (e.g., CDC Maxim)
30 – 45g
Small Green (e.g., CDC Viceroy)
30 – 40g
Large Green (e.g., CDC Impower)
60 – 80g
Example Calculation
If you are planting a Small Red lentil variety with a TKW of 40 grams, a germination of 95%, and you expect 90% survival with a target of 120 plants/m²:
In this scenario, you would set your drill to approximately 50 lbs/acre to achieve the desired plant stand.
Why Precision Matters
Under-seeding lentils often leads to increased weed pressure and uneven ripening, which complicates desiccation and harvest. Conversely, over-seeding can increase the risk of foliar diseases like Ascochyta blight or Sclerotinia due to a denser, more humid canopy. Using this Lentil Seeding Rate Calculator ensures you hit the "Goldilocks" zone for your specific seed lot.