This is something I wanted to know when my grand father said that the plants won’t grow if the garden is’nt ploughed.

What is ploughing & Why is it necessary?

Ploughing is the loosening and turning of the soil.
Ploughing is necessary as:
(1)It uproots undesirable plants-weeds.
(2)Helps mix nutrients and fertilizers uniformly.
(3)Helps increase soil microbes and organisms like earthworms who increse soil fertility.

@ aaryan 

ploughing helps the root to breathe , and respire . 
and it will also increase the air spaces of the soil . 
it helps the rooot to absorb minerals from deep inside the soil . 
it helps make the soil fertile . 
it allow the soil to mix up with fertiliser . 
hope it clears your doubt 
all the best ..