This fundamental post-harvest step relies on a current of air to blow away lightweight husks, straw, and dust from the heavier, edible seeds. While early methods relied on tossing grain in the wind, combine harvesters and seed cleaners use powerful internal fans to achieve the same result continuously. Proper airflow adjustment prevents valuable seed from blowing out the back with the trash.
Turn down the fan speed before we winnow this batch, or you'll blow half the clover seed into the yard.
If the fan is set too high during this stage, farmers lose crop yield directly out the back of the machine.
Related terms
Combine harvester
A large self-propelled machine that reaps, threshes, and cleans grain crops in one pass.
Chaffy
Describing an ear of corn that has loose, poorly developed kernels and excess cob tissue.
Cleaning shoe
The assembly inside a combine harvester that separates the clean grain from chaff and small debris.
Thresh
To mechanically shatter harvested crop heads to separate the edible grain from the stalk and chaff.