Soil, Composition of soil, soil and water Relationship in detail


The upper layer of earth which have ability to grow a plant is called soil. Same as large quantity of water is required for a plant for optimum growth.

Composition of soil
Composition of soil

To understand the absorption of water we need to study the composition of soil and roots anatomy.

Composition of soil:

Heterogenous mixture of organic, inorganic substance, living organism, salt and topsoil water are part of soil composition.

  1. Organic matter
  2. Inorganic Mineral Particle
  3. Soil water
  4. Water content of soil
  5. Soil atmosphere
  6. Soil organism

Organic matter:

The remaining part of animal and plants are decomposed by microorganism that product is called organic matter. During decomposition process many gases and inorganic ions are release and colloidal organic residues is left. This is called hums and the process of making hums is called humification.

Inorganic Mineral Particle:

Sand, silt and clay particle are called inorganic mineral particle. These particles are also called soil separates. They are classified on the base of their size. The study of partial ratio is called soil texture. Mostly all topsoil are mixture of silt, sand and clay.

Clay particle are colloidal in nature and hold large amount of water.

Silt particle are non-colloidal and not absorbed water but part of capillaries in topsoil.

Sandy are porous in nature and root can penetrate fast in sandy particle.

Soil and water:

Water is second most important component in plant growth because they dissolve nutrients, salt and make available for plant

Gravitational Water:

The water move downward due to gravity is called gravitational water.

Water table:

The water present in permanent saturated zone is called ground water and its upper layer is called water table.

Capillary water:

The water present in capillary are called capillary water, this only saucer of water for plants.

Hygroscopic water:

Water present around the colloidal partial is called hygroscopic water. Plant only absorbed very small amount of water from this part.

Chemical Water:

Some of water are parts of many chemical compound in that part such as oxides of aluminum, silicon and iron.

Water content:

Field capacity:

The percentage of moisture content present in soils after slow drainage is called field capacity. It usually founded in 5-40%. The field capacity also indicates that point at which cohesion and adhesion force equal.

Water content of the Topsoil:

The weight of water in a given soil at 105 C temperature is called water content of soil. This weight in express in term dry weight.

Permanent wilting:

A condition in which water amount is reduce in capillary due to evaporation and transpiration by plant.

Deficiency of water occurred in capillary and insufficient amount of water effect on the plant growth. This is called wilting.

Earliest wilting is temporary due to hottest part of day, if continuously water deficiency of water occur they become permanent wilting.

According to scientist at -1.5Mpa water potential permanent wilting occurred.


The given soil pores filled with gases that condition is called soil atmosphere.

These gases are carbon dioxide, nitrogen and oxygen.  Carbon dioxide concentration high in topsoil as compare to atmosphere.

Poorly drainage upper part is also poor in gas that affect the growth of plants.


The upper part have diverse population of living microorganism both plants and animals. They include rodent, insect, fungi, bacteria and large tree root to worms.

They effect on plants physical, biological and chemical properties of topsoil. Some microorganism is helpful in plant growth some are harmful. Such as earthworm help in physical breakdown of plant residue.

Decomposer decompose the dead plant and make nutrient available for plants.

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