Soil is the uppermost layer of the Earth’s surface made up of weathered rocks, finer material like sand, silt and clay, together with organic matter. Soil forms a very thin layer but is of the utmost importance to us. This is so because it is the layer that supports plants, and plants provide food for all other living things. The organic matter in the soil is called humus. It is made up of the decaying remains of plants and animals. It provides nitrogen for the proper growth of plants. Soil takes a very long time to form and it is formed in layers. The uppermost layer or the topsoil is made up of fine particles of sand and humus. Most plants have their roots limited to this layer. The layer below the topsil is the subsoil. It is a more dense layer made up of coarse particles of sand, clay and some amount of humus. The next layer has rocks in their partially weathered from and below this is the layer of parent rock. The mineral composition of the soil in any region is derived mainly from its parent rock.