Niab Seed Rate Calculator

NIAB Seed Rate Calculator

Calculate the precise drilling rate in kg/ha based on NIAB standards.

Required Seed Rate

0 kg/ha

function calculateSeedRate() { var targetPop = parseFloat(document.getElementById('targetPop').value); var tgw = parseFloat(document.getElementById('tgw').value); var germination = parseFloat(document.getElementById('germination').value); var fieldLoss = parseFloat(document.getElementById('fieldLoss').value); if (isNaN(targetPop) || isNaN(tgw) || isNaN(germination) || isNaN(fieldLoss)) { alert("Please fill in all fields with valid numbers."); return; } // Establishment % calculation var establishment = germination – fieldLoss; if (establishment <= 0) { alert("Establishment percentage must be greater than zero. Please check your field loss and germination values."); return; } // NIAB Formula: (Target Population x TGW) / (Expected Establishment %) var seedRate = (targetPop * tgw) / establishment; document.getElementById('kgPerHa').innerText = seedRate.toFixed(2) + " kg/ha"; document.getElementById('breakdown').innerText = "Based on " + establishment.toFixed(1) + "% expected field establishment."; document.getElementById('seedResult').style.display = 'block'; }

Understanding the NIAB Seed Rate Calculation

Calculating the correct seed rate is critical for achieving optimal yield potential in cereal crops like wheat, barley, and oats. The NIAB (National Institute of Agricultural Botany) methodology ensures that farmers don't simply drill by weight, but rather by the number of viable seeds per square meter.

The Formula

Seed Rate (kg/ha) = (Target Population x TGW) / Establishment %

Key Variables Explained

• Target Plant Population: This is the number of plants you want to emerge per square meter. For winter wheat, this typically ranges from 250 to 350 seeds/m² depending on the drilling date.
• Thousand Grain Weight (TGW): The weight in grams of 1,000 seeds. This varies significantly between seed lots and varieties. A higher TGW requires a higher seed rate in kg/ha to achieve the same plant count.
• Germination %: Found on the official seed certificate. It indicates the percentage of seeds expected to sprout under ideal conditions.
• Field Loss %: An estimate of seeds that will not survive due to seedbed quality, pest pressure (slugs/birds), and weather conditions.

Practical Example

If you are drilling a winter wheat variety with a TGW of 50g, a target population of 300 seeds/m², and you expect an 85% establishment (95% germination minus 10% field loss), your calculation would be:

(300 x 50) / 85 = 176.47 kg/ha

Why Precision Drilling Matters

Using a seed rate calculator helps prevent two common farming issues:

1. Over-seeding: Leads to thick crops prone to lodging (falling over), increased disease pressure due to poor airflow, and unnecessary seed costs.
2. Under-seeding: Results in thin stands that allow weeds to flourish and fail to capture enough sunlight to maximize yield.

Note: Always calibrate your seed drill physically after calculating the theoretical rate to ensure accuracy across different soil types and forward speeds.