Winnowing

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Winnowing Introduction

Separating grains from chaff is called winnowing. It is an agricultural technique being used since ancient times. Now a days many machines are available for winnowing.


What is Winnowing? 

Winnowing meaning is separation of grains from straw by the use of current of air. The word winnow is originated from old English word ‘windwian’ which means separation of mixture through wind. 


Winnowing Definition

Winnowing can be defined as separation of heavier substance from lighter substance of a mixture using current of air or by blowing air. 


Wind winnowing technique is being used since ancient times to separate grains from chaff. It is very commonly used by farmers to separate husk from heavy grains. Husk is lighter than grains, so it gets removed by the force of air from the grains.


Principle of Winnowing

Winnowing is based on the fact that if mixture is containing two components and one is lighter than another one, then both the components can be separated by blow of air. Mixture is allowed to fall from a height. Lighter component gets separated from heavier component due to wind.


In the above image it is shown that as empty seeds and debris are lighter than filled seeds, so they get separated by current of air. 


Wind winnowing machines- It is said that first winnowing machine was developed by Andrew Rodger in 1737, in Scotland. He was a farmer and developed that machine for separating corn. He named the machine ‘fanner’. Then during industrial revolution, many types of winnowing machines were developed.

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Ancient winnowing machine developed in China 

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Modern Winnowing Machine 

Now a days, single machine is available for winnowing and threshing. Threshing is a process of separating stalks from grain. Farmers used to beat the grains manually to separate its edible part from non-edible part. Now a days, machines are available for threshing also. Even now a days farmers use only one machine for threshing and winnowing. It makes their work easy and they can complete two tasks at a time. This saves their time and energy. 

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Single machine for winnowing and threshing 


Example of Winnowing 

  1. Wheat is separated from husk by using winnowing method. Wheat and husk mixture is allowed to fall from a height. Husk being lighter than wheat grains get separated from wheat because of wind or air blow. 

  2. Dirt particles can be removed from grains by winnowing. 

  3. Corns are separated from straw by winnowing.


Advantages of Winnowing

  1. Winnowing is very useful in agriculture. 

  2. We get grains and husk separate by winnowing, so husk can be used as food for animals.

  3. We can separate grains such as wheat, corn, millet etc. from lighter impurities such as husk, straw, stones etc. by using winnowing. 


Disadvantages of Winnowing

  1. This process of separating the components of a mixture does not work for heavier particles such as stones. 

  2. Since in winnowing the components of a mixture are separated with the help of wind, it is practically not possible to separate the components that are heavier than grains. Therefore, this process of separation of mixtures has a limited scope.

  3. Also, winnowing machines are more efficient than manual winnowing.


Difference Between Winnowing and Threshing 

S.No. 

Winnowing 

Threshing 

1. 

It is the process of separating husk from grains. 

It is the process of loosening edible part (grain) from non-edible part (chaff).

2. 

Farmers used to do it by making the grains and husk mixture to fall from the height. During this process husk gets separated by wind. 

Farmers used to do it by striking the crop on the hard surface. 

3. 

It is done after threshing. 

It is done before winnowing.