this preparation of soil also known as ploughing is done to level the soil and bring the under nutrients up and up to down.this tilling of soil also control the weeds.

Tilling involve digging about a spade deep, and putting the soil back in the ground, but inverting the top and bottom layers.
Both layers contain different sets of organisms, for instance aerobic bacteria that require oxygen in the top soil, and anaerobic bacteria in the bottom layer. You basically kill most of both kinds every time you till.

Tilling is a great mechanical way to get rid of weeds, as they will decompose when put upside down under the ground with no sunlight available, but it is currently viewed as bringing about a few flaws, among which:

• Soil compaction : Tilling means heavy equipment will compact the soil in a job that is now viewed as unnecessary. Plant roots can 't penetrate the bottom soil easily and it stresses the plants and reduce productivity.
• Tillage pan : Because tilling always happen at the same depth, a watertight crust forms at the level separating the tilled soil from the still soil. This layer makes it harder for the plants to break through or for the nutrients to penetrate deep.
• Erosion : A tilled soil is totally exposed to the action of rain without protection. Such naked soil is more likely to run off and erode.

In recent agronomy, tilling is not one of the best farming practices anymore.
Tilling involve digging about a spade deep, and putting the soil back in the ground, but inverting the top and bottom layers.
Both layers contain different sets of organisms, for instance aerobic bacteria that require oxygen in the top soil, and anaerobic bacteria in the bottom layer. You basically kill most of both kinds every time you till.

Tilling is a great mechanical way to get rid of weeds, as they will decompose when put upside down under the ground with no sunlight available, but it is currently viewed as bringing about a few flaws, among which:

• Soil compaction : Tilling means heavy equipment will compact the soil in a job that is now viewed as unnecessary. Plant roots can 't penetrate the bottom soil easily and it stresses the plants and reduce productivity.
  
• Tillage pan : Because tilling always happen at the same depth, a watertight crust forms at the level separating the tilled soil from the still soil. This layer makes it harder for the plants to break through or for the nutrients to penetrate deep.
• Erosion : A tilled soil is totally exposed to the action of rain without protection. Such naked soil is more likely to run off and erode.

More and more American farmers have adopted the "no-till" cultural practice, which consists in leaving the soil as it is after harvest, or maybe planting green manure, and planting the new crop directly in the soil that still has the stubbles of the old crop in it.
However, no-till relies heavily on genetically modified plants that produce their own pesticide in order to reduce the number of tractor passages.
The Fukuoka method of farming is an organic gardening method that does not use tillage, but it does not suit intensive organic farming

it is important because

1 it helps the roots to penetrate deep into the soil.

2 it makes the soil porous due to which exchange of gases becomes easy

3 it increases the no of friendly microbes

4 they further loosen the soil and add humus to it

it helps in better penetration of roots.

it helps in growth of soil friendly mibrobes.

it increased water holding capacity of soil.

it brings nutrient rich soil to the top.