Tips on Identifying Threshing/Harvesting Losses

September 19, 2023

Part 2

It is not uncommon for the combine harvester to leave grain behind. The loss percentage still needs to be measured to determine whether or not the machinery needs adjustments.

In this second in a two-part series of blog posts, you will learn how to calculate the loss percentage and understand the source of the grain losses left on the ground.

A fiew points

  • The producer should aim for no more than a 3% loss to achieve acceptable profitability.
  • A poorly adjusted combine can cause losses as high as 15%.

Talking about the weather

Soybeans are usually harvested when the leaves have dried and dropped from the plants and the seeds are mature. However, some weather conditions can adversely affect the harvesting process.

In damp weather, the soybean plants may stay wet. The pods are more fragile then and can split open or shatter. Harvesting still has to be done, since the more the season progresses, the greater the risk of the soybean pods shattering.

Soybean losses

  • Pre-harvest losses: Poor weather conditions, diseases and insects, the timing of the harvest.
  • Header losses: Improperly positioned reel, missing knives or fingers.
  • Machine leakage losses: Cleanout trap is open or poorly adjusted, missing or broken seal, holes.
  • Separation losses: Wrong concave (rotor) speed, concave blocked or incorrectly spaced, green immature crop.
  • Cleaning losses: Passes incorrectly adjusted, poorly adjusted fan speed

A = Preharvest losses

B-A = Header losses

C-B-A = Machine leakage

D-C-B-A = Threshing, separation and cleaning losses

Key steps in determining harvest losses

  1. Make a square 1 ft² frame.
  2. Place the frame on the ground behind the combine and count the number of seeds on the ground within the frame.
  3. Estimate the size of your soybeans: For small soybeans size, 5 soybeans / ft² is approximately equal to 36.744 kg loss/acre. For medium soybeans size, 4 soybeans / ft² is approximately equal to 36.744 kg loss/acre.
  4. Estimate your percent loss (100 x measured loss / yield).

How to determine your losses

Relevant information:

  • One acre contains 43,560 ft² .
  • A bushel of soybean at 13% moisture weighs 36,744 kg
  • Soybeans generally range from 5500 seeds / kg to 7000 seeds / kg.

Table of Soybean Harvest Loss Calculation in kg per acre.


  • If your losses represent 3% or less, your combine-harvester is doing a good job.
  • If your losses exceed this percentage, you will need to do some tests to determine where the losses are occurring and if they can be reduced.

* This is the second in a two-part series on soybean threshing.

If you haven’t already, we invite you to read the first article: Pre-Harvest Combine Adjustments.  

Happy harvest !