Question

why is it necessary to plough the soil

Answer 1

Seeds are typically only planted an inch below the soil surface. Farmers want to give those seeds the best chance of germinating and growing. That means mechanically preparing seed beds by breaking the ground. Soil can become dense and compact. Plowing also makes it easier to plant. Plowing breaks up the blocky structure of the soil which can aid in drainage and root growth

Answer 2

Ploughing the soil helps in mixing the weeds which might have grown when the field was fallow, with the soil. Ploughing also helps the roots to penetrate deep inside the soil as it helps the air to go in the soil