Horizons of soil - class-V

Climate is a primary factor in soil formation, as temperature and precipitation influence the rate of chemical and physical weathering of parent rock.

Rate of decomposition of detritus depends upon chemical mature of detritus, temperature, soil moisture and soil pH. A soil temperature of 25oC and more hastens decomposition. A low temperature of less than 10oC reduces the rate of decomposition. Moisture is essential for decomposition. Excessive moisture also impedes decomposition probably due to anaerobiosis. Neutral and slightly alkaline soils are rich in detritivores, earthworms and decomposer microbes. Acidity decreases the number of detritivores and earthworms. Soil with a small amount of lignin/chitin/cellulose and rich in nitrogen and water-soluble substances(like sugars), decomposes rapidly.

Clayey soil has fine particles that hold water well and can be molded into shapes, making it ideal for pottery and toys.

As we know, the soil is made up of many layers. These layers are called horizons. The topmost among these layers is A horizon. It is the layer parallel to the soil surface. It is rich in organic matter. It also contains humus, which is necessary for the proper growth of plants. Thus, we can say that A horizon has many necessary ingredients to support the plant and animal life.

The horizon B is also known as the layer of subsoil. It is light brown in colour. it has lots of iron and clay minerals accumulated inside it. this layer contains more soluble minerals and clay inside it and so the plant roots reaching here can get maximum mineral content for their growth and development.

Soil is one of the most important abiotic resources of the environment. It provides habitat to a vast number of living organisms. It holds the roots of plants and trees. It provides the necessary nutrients to the plants when their roots absorb water from the soil, along with minerals and organic matter present in the form of humus in the soil. Soil also has spaces between its particles, providing space for air and water to percolate into it. So, the soil is a mixture of minerals, organic matter, air, and water.

Clay particles are extremely small in size. They also have a large surface area owing to their small sizes. So they can absorb a large amount of water. Apart from this, clay particles also have very little space between their particles. So, their water retention capacity is also less. 

Sandy soil has large-sized particles. These particles are loosely bound to each other. Apart from this, they also have large interparticle spaces between them. A lot of air can be trapped in this space. Same is the case with silt. Its particles are water holding capacity is more.

Bedrock is the lowermost layer of soil. It lies beneath the soil layers. It is hard and made of rocks. Its constituents are tightly bound to each other. 

Soil is arranged in various layers. These layers collectively form the entire structure of the soil. This is called a soil profile. The soil profile is made up of different layers, called horizons. A soil horizon is a layer of soil that runs parallel to the soil surface. Each of the layer has different and specific characteristics that are different from the other layers.

Humus is the organic component of soil, formed by the decomposition of leaves and other plant material, often found on top layers.

Weathering is the breakdown of rocks, minerals, and soils through contact with the atmosphere, water, and biological organisms, which is the first step in soil formation.

Humus is formed from decaying organic matter (leaves, twigs, etc.) that accumulates on the surface of the ground.

The soil layer is made up of R Horizon It is only between $5$ to $10$ inches thick and consists of organic matter and minerals. This layer is also called subsoil.

A vertical section through different layers of the soil is called the soil profile.