Points to remember


  • Threshing is usually done in the field, near the field or at the nearest road.
  • Usually, a machine thresher works with a drum as axial.
  • The crop turns around an axial.
  • The drums have “teeth” on the surface.
  • The teeth of the drum separates the grains from the straw by beating it.



  • Cleaning is one of the last methods of harvesting process.
  • Cleaning grain means removing all the materials other than grain.



  • Grain cleaning is important as it removes unwanted materials from the grain.
  • Clean grain has a higher value than grain that is contaminated with straws, chaff (seed coverings and tiny pieces of leaves or stem), weed seeds, soil, rubbish, and other non-grain materials.
  • There are some cleaning methods:
  • Winnowing
  • Screening
  • Seed cleaning



  1. It is a method commonly practised by farmers to separate pieces of chaff from the grain by wind or blowing air.
  2. In this process; lighter materials like unfilled grains; chaff; weed seeds; and straw can be removed from the grain by using a blower; air fan; or by wind.



  • Screening is a method of separating particles according to size.


Seed cleaning:

  • In this method, any debris or low quality, infested or infected seeds and seeds of different species (weeds) are removed.



  • It is an excellent method of controlling pests especially when few plants are infested.
  • It is the easiest and direct way to kill the visible and slowly moving pests.