10.3. SOIL FORMATION

Soil is the top fertile layer of the Earth’s surface where plants grow. Soil is also an ecosystem with its own biocenosis and biotope which change often. Soil consists of: 45% mineral matter, 25% water, 25% air and 5% organic matter.

1. Bedrock begins to disaggregate by wind, rain and snow. Smaller rock particles mix with other sediments.	2. Breakdown of rocks is accelerated by some bacteria, lichen and fungi. Rock particles are tiny and have nutrients.	3. Small plants and many invertebrates (eg. worms) colonize the topsoil. Soil thickness keeps increasing.	4. Plant roots of different sizes make the soil more porous, which increases the amount of nutrients and its fertility.