Why Is the First Layer of the Soil Profile the Most Important?

Growth Medium

• The first layer of soil is the medium for plant roots. Within the top layer are all the nutrients that plants need. In some areas, this layer might only be a few inches thick, while in others where the land has not been disturbed, it may reach several feet below the surface. Plants' roots thrive in this soil and hold it in place against erosion.

Decomposition

• The top layer of soil usually holds undissolved minerals in clay. Microbes, fungi and a whole underground world of life that work constantly in the decomposing of organic matter live within the top 12 inches of soil, where water and air are usually plentiful.

High Demand

• There is a high demand for good topsoil in construction projects. Many urban areas no longer have their original layer of topsoil, and so any projects requiring resurfacing of the soil need to bring in the necessary soil. Without a good layer of topsoil, landscaping plants or lawns will struggle to live without the necessary nutrients available to their roots.

Weathering Takes Time

• The process of wearing away by wind and rain, combined with the life of the subsoil, takes years to build a 12-inch layer of dark soil that's rich in nutrients and minerals. Metals rust and decompose; glass chips and fragments; wood rots and crumbles; paper disintegrates; concrete erodes into sand. These elements all stay within the top layer of the soil. Plants root readily, grow, die and decompose, adding organic components to the mix.