Why farmers need to separate grains from the chaff?

The method of separating grains from chaffs is known as threshing.

This process is performed to separate the edible part of the grain or seeds (or other crops) from the straw and chaff.

The process can be done manually by beating it on a solid surface or by using a threshing machine.

Stalks or stems of crop plants and the chaff are soft material whereas the grains themselves are very hard, therefore after striking it the heavy hard grains get detached from the soft stalks.