Why do Soils Differ?

There are numerous reasons why soils differ regionally. The most influential factors include the parent material (the rocks from which the soil has come), the climate and terrain of the region, as well as the type of plant life and vegetation present, and, of course, human influence.

Parent material - this refers to the original underlying rock upon which the soil formation takes place. Essentially, the nature of parent rock in a particular region will affect the type of soil that eventually develops. For example, in an area of mainly sandstone, the soil formed due to the weathering of the rock is likely to be well-drained, course and sandy.

Climate – The world consists of a broad range of climatic regions, each with its own specific types of soil. A common example of this is tundra soil, which tends to occur mainly in northern-hemisphere areas such as the Arctic and Scandinavia, where the climate is often cold and hence the organic materials do not break down very easily and peat tends to form. In contrast, red and grey ‘desert’ soils which are found only in hot, arid regions, such as Africa and the Middle-East, contain very small amounts of organic material because it is rapidly oxidised under the warm conditions. These soils but are less leached than the tundra soils.

Terrain – this is another important factor in soil development. Areas with many slopes in the land tend to have more freely drained soils, as water can run off or percolate more rapidly. In contrast, regions with mostly flat areas of land can often be waterlogged, because of the lack of gradient to promote lateral or sideways flow.

Plants – The type of plant life and vegetation obviously varies according to a region’s climate and other factors. Plants also have a strong influence on soil development – they take up nutrients from the ground, whilst adding organic material to the soil surface.

Humans – We should not forget the influence of man who has managed the land over the last few thousand years. Agriculture, in particular, has had a big influence on developing the soils we see today.