Definition Composition Types and Formation of Soil
Our Earth is filled with vast amounts of water bodies as well as enormous trees surrounding us. Do we ever wonder how such big trees stand strong for years and years without any disruption? It is with the help of nothing but the soil. Soil is a part of our mother Earth and it has played a big role in growing plants that provide us with basic resources in our day-to-day life. We cannot ignore the fact that how many trees have been growing and giving us shelter with the help of this soil. But, how does this soil not wear out and keep trees strong? Well, it is because of moisture in the soil.
What is Moisture?
A small amount of wetness is known as moisture. Anything that has little amount of water in it is termed moisture. A small amount of water is nothing but water evaporates before it is collected in a small quantity. Likewise, soil too contains moisture, which helps in the growth of the trees.
Moisture in Soil
Unsaturated water contains a total amount of water along the water vapour. Soil does not come in contact with the water bodies like rivers, lakes, etc. But it has little left in it, enough for the plants that grow in it. Moisture in soil is as important as sunlight to plants because soil moisture helps in transferring required nutrients from the soils to the plants.
Types of Soil Moisture
There are three main types of soil water depending on the interaction of water with soil. They are,
Gravitational Water
The concept of gravity applies to moisture too. Water does not stay in the soil for a long time and is drained away immediately. Only a fraction of water molecules remain here. This happens mainly because of the large pores in the soil.
Capillary Water
In this type, the water molecules are trapped in the soil’s microspores. The water molecules here are more available than the gravitational water. They are not dried out easily, but once the soil is dried up, the water is forced to go down, converting it into gravitational water.
Hygroscopic Water
This is the strongest of the types of soil moisture. This not only stays in the soil pores but is available at the surface of the plants. They don’t dry up easily and keep the plants hydrated for a long time.
How Will You Show that Soil Contains Moisture?
Identifying moisture in the soil is as simple as finding a red ball in a pool of yellow balls. Moisture mainly consists of a small amount of water, which can be identified by heating up the soil. Heating something that has water will cause water to vaporise. Likewise, heating soil in a tube will convert water to water vapour, and the presence of water droplets on the sides of the tube confirms the moisture in the soil.
Using Soil Moisture For Plant Growth
A sufficient amount of moisture in the soil is necessary for the plant to have steady growth. Farmers need to be very careful with this process as an excess amount of water can destroy the roots of the plants. The moisture level in soil needs to be in the range of 20% and 60%. Less amount of soil moisture can lead to wilting of plants. Hence, controlling the range of soil moisture is the right necessity.
Soil Humidity
Humidity is nothing but the hot air surrounding it. Humid air is a problem for plants as it disrupts their routine of transpiring. Humidity also causes root disease, less growth, low quality of plants etc. plants are affected by humidity in both ways, i.e. when it is high or low. If the humidity is high, it affects the soil, drying it to the core. If it is low, it affects the growth of the plants, making it less desirable.
Hence, from this, we understand how humidity can affect the transpiration of life. Humidity is calculated through a hygrometer. It is said that black soil has the most humidity among the other soils, ranging from 150-200 mm/m.
Interesting Facts
About 95% of all food production is supported by soil.
It can take up to 1,000 years to form one centimetre of soil.
A quarter of all known species on earth call soil their home
Clay soil has the highest water-holding capacity among the other soil.
Key Features
Soil moisture controls the exchange of water and heat energy through evaporation and transpiration.
Soil moisture plays an important role in the growth of plants and also helps in agriculture.
There are three types of soils. Gravitational, capillary, and hygroscopic water.
FAQs on What Is Soil in Biology
1. What is soil?
Soil is the upper layer of the Earth’s surface made of minerals, organic matter, water, air, and living organisms that supports plant life. It forms through the weathering of rocks and the decomposition of plants and animals. Soil acts as a medium for plant growth, a habitat for organisms, and a key component of terrestrial ecosystems.
2. What are the main components of soil?
The main components of soil are mineral particles, organic matter (humus), water, air, and living organisms. These include:
- Mineral particles – sand, silt, and clay derived from rocks
- Humus – decomposed plant and animal material
- Water – dissolved nutrients for plants
- Air – oxygen for root respiration
- Soil organisms – bacteria, fungi, earthworms, and insects
3. How is soil formed?
Soil is formed by the gradual breakdown of rocks through weathering and the accumulation of organic matter over time. The main steps include:
- Physical weathering – rocks break into smaller pieces
- Chemical weathering – minerals change due to reactions with water and air
- Biological weathering – organisms contribute to rock breakdown
- Decomposition of plants and animals forming humus
4. What are the different types of soil?
The main types of soil are sandy soil, clayey soil, silty soil, and loamy soil. They differ based on particle size:
- Sandy soil – large particles, drains quickly
- Clayey soil – very small particles, holds more water
- Silty soil – smooth texture, retains moisture
- Loamy soil – balanced mix of sand, silt, and clay; ideal for agriculture
5. What is humus in soil?
Humus is the dark, organic component of soil formed by the decomposition of dead plants and animals. It improves soil fertility by:
- Increasing nutrient availability
- Enhancing water retention
- Improving soil structure and aeration
6. Why is soil important for plants?
Soil is important for plants because it provides nutrients, water, anchorage, and oxygen for root respiration. Specifically:
- Supplies essential minerals like nitrogen, phosphorus, and potassium
- Stores water for absorption by roots
- Anchors roots firmly in the ground
- Allows gas exchange for healthy growth
7. What are soil horizons?
Soil horizons are distinct layers of soil formed during the process of soil profile development. The main horizons include:
- O horizon – organic layer with leaf litter
- A horizon – topsoil rich in humus
- B horizon – subsoil with accumulated minerals
- C horizon – partially weathered parent material
8. What is the difference between soil and dirt?
Soil is a living, structured system that supports plant life, whereas dirt is simply displaced or degraded soil. Key differences include:
- Soil contains minerals, humus, organisms, air, and water
- Dirt lacks structure and biological activity
- Soil supports ecosystems, while dirt does not
9. What organisms live in soil?
Soil is home to a diverse community of microorganisms and small animals that maintain soil health. Common soil organisms include:
- Bacteria – decompose organic matter and fix nitrogen
- Fungi – form mycorrhizal associations with roots
- Earthworms – improve aeration and nutrient mixing
- Insects and protozoa – aid in decomposition
10. How does soil support ecosystems?
Soil supports ecosystems by acting as a foundation for plant growth and nutrient cycling. It contributes by:
- Providing nutrients through biogeochemical cycles
- Storing and filtering water
- Supporting biodiversity of plants and soil organisms
- Regulating carbon through carbon sequestration
