Soil is considered the "skin" of the Earth: it is the top layer of the Earth's surface.

Soil is a mixture of minerals, rocks, air, water, sand and humus. Humus is organic matter: the remains of dead plants and animals. Humus is very important because it is full of nutrients for plants.



LAYERS

Basically, soil is made up of 3 layers:

  • Topsoil: there is a lot of air, water and humus, so plants concentrate their roots here to obtain nutrients. Small animals also live in the topsoil: ants, worms, snails,...

  • Subsoil: there is little humus, air and water, so few living things can live in the subsoil.

  • Bedrock: it is made up of large rocks. There is very little water and air, so no living things can live here.



Soil Structure.jpg



TYPES

The proportion of water, air and humus in soil is not always the same. That is why there are different types of soil:

  • Fertile soil: it contains lots of water, air and humus, so plants can grow very well in this type of soil.

  • Poor soil: it contains little water, air and humus, so a few plants can grow here (e.g. olive trees and cereals).

  • Arid soil: it contains very little water and air. It doesn't contain humus. Only plants like cactuses can grow in arid soils.

Let's review what we have learned with a couple of videos.








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