Seed Lot Blending & Weighted Germination of the Mix
Blends cereals
Enter the weight and germination of two seed lots to get the weighted-average germinationof the blend — useful to use up a weaker lot without dropping below the minimum certification standard.
Blend two seed lots
Next: label the combined lot at 84% germination over 1,000 kg and adjust your seeding rate to the blended figure, not either lot alone.
Blending is a weighted average by mass — mixing a small high-germ lot into a large weak lot barely lifts the blend. Re-test germination after blending if lots differ widely.
Seed lot blending — key facts
- Blend germ
- (w₁·g₁ + w₂·g₂) ÷ (w₁+w₂)
- Total weight
- weight₁ + weight₂
- Type
- weight-weighted average
- Limit
- never beats the stronger lot
- Use case
- lift a marginal lot to standard
- Certified min
- often 80–90% germination
- Re-test
- needed if blend is sold/certified
- Privacy
- Runs in your browser; nothing uploaded
Use up the weak lot without dropping below standard
Few farms finish a season with seed lots that all test the same. You may have a big, strong lot at 92% germination and a smaller leftover at 78% — too weak to certify on its own, too good to throw away. Blending the two makes one composite lot, and because each lot contributes seed in proportion to its weight, the result is a weight-weighted average, not a simple midpoint. The bigger, stronger lot pulls the blend up; add too much weak seed and it sinks below the line.
This tool gives the total weight, the blended germination, and each lot's contribution the moment you enter both weights and germinations. Use it to test ratios until the blend clears your minimum certification standard, then re-figure your sowing with the new germination. Pair it with the Seed Germination Test, Seedling Vigour Index and Seed Rate calculators for a complete pre-sowing seed plan.
Use up weak seed
Blend a marginal lot instead of binning it.
Stay above standard
Test ratios until the blend clears the line.
Build one uniform lot
Even out variation across batches for a field.
Re-rate the sowing
Adjust seed rate to the blend's germination.
Frequently Asked Questions
What is seed lot blending?+
Seed lot blending is mixing two (or more) batches of the same seed to make a single composite lot. It is commonly done to use up a smaller or weaker lot by combining it with a stronger one, so the blended seed still meets the germination and quality standard you need for sowing or sale.
How is blended germination calculated?+
It is a weight-weighted average, not a simple average. Blended germination = (weight₁ × germ₁ + weight₂ × germ₂) ÷ (weight₁ + weight₂). For example 800 kg at 92% blended with 200 kg at 78% gives (800×92 + 200×78) ÷ 1000 = 89.2%. The bigger lot pulls the result toward its own germination.
Why use a weighted average instead of a simple average?+
Because each lot contributes seed in proportion to its weight. A simple average of 92% and 78% is 85%, but if the 92% lot is four times larger, the real blend is closer to 89%. Weighting by weight gives the true germination of the mixed seed you actually sow.
Why blend seed lots at all?+
Blending lets you use up a weaker lot without discarding it, even out variation between batches, build one uniform lot for a large field, or rescue a lot that sits just below standard by adding stronger seed. It is a practical way to avoid waste while still meeting a minimum germination requirement.
What is the minimum certification standard?+
Most certification schemes set a minimum germination (often 80–90% depending on crop and class) below which seed cannot be sold or labelled as certified. Blending is useful precisely because it can lift a marginal lot above that line — but only if the stronger lot is large enough to pull the weighted average up.
Can blending make a weak lot pass the standard?+
Only within limits. The blend can never exceed the better lot's germination, and the more weak seed you add, the lower the blend. Use this tool to test ratios: enter different weights and watch the blended germination so you blend just enough strong seed to clear the standard.
Does blending change the seeding rate?+
Yes — because the blended germination differs from each lot, you should re-figure your seeding rate from the blend's germination, not from either original lot. Use the Seed Rate calculator with the blended germination % this tool gives you to adjust kg/ha for pure live seed.
Does this work for any crop or weight unit?+
Yes — it works for cereals, pulses, oilseeds, vegetables or forage seed. Enter both lot weights in the same unit (kg, quintal, lb or bag) and the germination of each as a percentage; the weighted blend germination is unit-independent.
Are the figures precise?+
The arithmetic is exact for the weights and germination percentages you enter. Real germination is only known to the accuracy of your seed test, and blending assumes thorough mixing. Re-test the composite lot if it is going to be certified or sold, and treat the result as a strong planning figure.