Question

why is it necessary to loosen the soil before sowing?

Answer 1

because only loose soil allows the roots to penetrate freely deep into the soil. The water also can reach easily up to more depth in loose soil.

Answer 2

loosening the soil before sowing has the following advantages:

1) it permits easy and deeper penetration of the roots
2) it provides good aeration to the roots
3) it retains moisture for a longer period 
4) it exposes soil pests to natural predators
5) it helps in uprooting the weeds
6) it promotes growth of useful microorganisms in the soil