For what purpose and why organic and inorganic fertilizers are applied to the soil and why it has to be done annually.

The main factor of soil fertility is the humus layer is less than 5%. Fertilizers are applied to the soil to replenish it with nitrogen. Plants use only 40-50%, the rest is reduced to volatile compounds or washed out of the soil. Therefore, fertilizers must be applied daily. With insufficient application and application of fertilizers, the soil is quickly depleted and yields are reduced.