But steeper slopes may be prone to erosion, removing all or part of the topsoil and subsoil, leaving weakly developed soil. Time It may take hundreds of years to form one inch of soil from parent material. Only the top few inches of soil can sustain plant growth. Every soil is unique. Indeed, scientists have named thousands of different soils around the world.
Soils are very precious.
Continents cover less than half the planet, not all land regions are covered with soil, and not all soils are well suited to agriculture or plant growth. Thus, the soils that our needed for our survival cover far less than half the earth, and they are very, very thin. If you dug a five-foot pit in a forest, a grassland or a field of corn, you would see that the side of the pit displays horizontal soil layers of various colors and textures. Each layer is called a horizon . Soil scientists describe and name soils based on the horizons in the top 48 inches.