Question

two tyre of a tractor are very wide and huge .why

Answer 1

Because broad tyres have large area of contact and less pressure on the ground.
➡Because of this, heavy vehicles (like tractor) can move even on soft roads and fields without sinking.

Answer 2

We know that more area means less pressure.

Since, weight of tractors are preety heavy that is why we uses broad tire so as to divide its weight equally and hence, it prevents sinking of tractor in soil.