Forces of Change

What Is Soil?

Soils Make Life

Plants grow in and from soils, and plants—directly or indirectly—feed almost all life on Earth.

Life Makes Soils

Soil-dwellers such as bacteria and fungi recycle once-living organisms into nutrients and soil organic matter (humus)—vital components of all soils.

Without soils, life would not exist as we know it.

Farm soil
A teaspoon of good farm soil contains up to 1 billion bacteria in more than 4,000 species.
© L. Clarke/Corbis

Soils Breathe

From burrowers to bacteria, the organisms that live in soils respire. Most of them take in oxygen to do their work, and they give off carbon dioxide, just as humans do.

Soils breathe because they shelter and support living organisms.

Soil or Dirt?

Soils are more than dirt. Dirt is a mixture of minerals, air, water, and living and dead things. The possibilities are almost endless—bugs, bacteria, fungi, feces, nematodes, worms, roots, rotting plants, ice, minerals…

Soils have history! Their unique, colorful and exotic layers give us clues to how they have changed over time.

Soils are more than the sum of their parts.