Discuss the factors responsible for soil formation and also the process involved.

Besides, a long period action of climate reduces the differences caused by parents materials. Where there is short period action of the climate, the properties of parent material reflect the soil. Hence the same parent material may produce two types of soil in two climatic regions and two different parent materials may produce a single type of soil in a particular climate region.

For example, the sandy soils of the desert are derived from sandstone and granite rock as well. These soils are formed under the hot desert climatic conditions. On the other hand, crystalline granite rocks produce laterites in the moist climate conditions of Rajmahal hills and the dry chilka soil in the drier regions of Andhra Pradesh.

3. Biological Activity : Biological organisms also play an important role in the soil formation. Plant life consists of trees, shrubs, grasses, bacteria and fungi. Dead plants provide humus to the soil. Humus maintains the fertility of the soil.

The climatic conditions determine the activities of the living organisms (bacteria and fungi). These organisms are more active in humid tropical and sub-tropical climatic regions and their activities are limited in cold climatic areas. Hence, they consume humus and make the soil poor in tropical and sub-tropical regions and rich in cold climatic areas because of the limited activities of living organisms. Thus the soils of humid tropical and sub-tropical climatic regions are poor and the soils of cold climatic regions are rich.

Moreover, the acidity formed by humus is also limited in the soils of humid tropical regions. Hence, a high proportion of mineral contents are found in the soils of these regions. These mineral contents also make the soils poor. Bacteria also change the gaseous nitrogen of the air into chemical form which can be consumed by plants.
4. Topography : Like parent materials, topography of a region is a passive control factor in the soil formation. The topography determines the amout of exposure of a surface covered by the parent materials to sunlight and the amount of surface and sub-surface drainage over and through the parent materials. Soils will be thin on steep slopes and thick over flat upland areas. Soil formation is particularly favourable on gentle slopes where erosion is slow and percolation of water is good. Accumulation of organic matter giving the soil dark colour, with thick layers, is observed over flat areas. In mid-latitudes, the south facing slopes exposed to sunlight have different conditions of vegetation and soils and the north facing slopes with cool, moist conditions have some other soils and vegetation.

5. Time : It is the most important factor in the soil formation. The length of time the soil forming processes operate, determines maturation of soils and profile development. When the soil-forming processes act for a sufficiently long time, developing a distinctive soil profile, the soil becomes mature. Soil developing from recently deposited alluvium or glacial till are considered young and they exhibit no horizons or only poorly developed horizons. There is no specific time frame of the maturation for the soils.