Separating grains from chaff is a process known as winnowing. Winnowing is an ancient agricultural technique used to separate the valuable grains from the unwanted materials such as husk, straw, and chaff. This process is primarily performed after the threshing process, where the grains are separated from the stalks.

Process of Winnowing:
1. Collection of Harvested Crops: The first step in the winnowing process involves collecting the harvested crops, which typically contain a mixture of grains, straw, chaff, and other impurities.

2. Preparation of Winnowing Area: A suitable area is prepared for winnowing by spreading a clean cloth or tarpaulin on the ground. This helps in collecting the separated grains and preventing them from getting mixed with the chaff.

3. Throwing the Mixture: The mixture of grains and chaff is then thrown into the air from a certain height. This is usually done using a winnowing basket or a winnowing fan.

4. Effect of Air Currents: As the mixture is thrown into the air, the grains being heavier than the chaff tend to fall down vertically due to gravity. At the same time, the chaff, being lighter, gets carried away by the wind or air currents.

5. Separation of Grains and Chaff: As a result of the air currents, the grains fall near the winnowing area, while the chaff is carried away and gets scattered in different directions.

6. Repeat Process: The process of throwing the mixture into the air is repeated multiple times until a significant separation of grains and chaff is achieved. This ensures that most of the unwanted materials are removed, leaving behind only the valuable grains.

7. Collection of Grains: Finally, the separated grains are collected from the winnowing area and stored in containers for further use or processing.

Advantages of Winnowing:
- Winnowing is a simple and cost-effective method of separating grains from chaff, requiring minimal equipment.
- It helps in removing impurities and unwanted materials from the harvested crops, ensuring the quality of the grains.
- The process can be easily performed by farmers in rural areas without the need for sophisticated machinery.
- It is an environmentally friendly method as it does not require the use of chemicals or excessive energy.

winnowing is the process of separating grains from chaff using air currents. It has been a widely used technique in agriculture for centuries and continues to be practiced in many parts of the world. This traditional method of grain separation plays a crucial role in ensuring the quality and purity of the harvested crops.

As we know, before winnowing ,the grain and chaff are mixed and also know grains are havier than chaff now, at the time of winnowing grains are fall directly down whereas chaff are lighter than grains so chaffs are thown farer than grain by wind blown by fan or machine.