Winnowing is the process of removing lighter contaminants like straw, chaff, dust etc either by dropping the materials from a height against natural wind then fanning manually or by using a mechanical blower.
Guidelines for good winnowing methods:
1. A polyethylene sheet is spread on the ground.
2. The uncleaned grain is placed in the winnowing tray.
3. It is dropped from a height of about 1.5m against the natural wind to separate the light undesirable materials.
4. Fanning manually with the winnowing tray does further cleaning.
5. Hand/ power operated fan/blower may be used if natural wind is not enough and to reduce human drudgery.
6. The heavy undesirable contaminants still remain with the grain which can be removed with a grader