Question

.Is it necessary to soak seed in water before sowing? why?..

Answer 1

when the seed absorbs water it's coat becomes easy to be broken by the emerging root or shoot

the bad seeds will float while the good ones will remain inside water

Answer 2

By soaking seed in the water bad quality seeds will be identified by you and this will help you to sow good quality seeds. Seeds which are good in quality will start germinating in water where as the seed which are bad will not germinate.