What is soil? How soil varies in different places?

Soil is the layer of loose material between the surface and the solid rock below the ground.  Chances are that you haven’t thought a lot about the soil under your feet, but you may be surprised at the complexity of soil. Soil varies in its composition and the structure of its particles, and these factors are closely examined by farmers, who need appropriate soil for planting crops, as well as engineers who may need to understand how soil is going to hold up under different demands. Soil is also vitally important to the sustainability of an ecosystem because it serves as the natural medium for the growth of vegetation. Nothing can grow on Earth without it, but the soil varies in different places.


The soil is rich in nutrients, so many grasses can grow healthy and quickly.  They are an important source of food for man; they play an important ecological role in nature; and they are good protectors of the soil against soil erosion. The greatest value of grass is perhaps the role that grass plays in stabilizing and protecting the soil and for this reason the grass family is probably the most important plant family on earth.

Long roots:

Trees and grasses have long roots that go deep down to collect as much water as possible from the soil. Roots grow through the whole life of the plant. They grow longer from the tip, adding cells to the end of each root. The root adds cells to their tips, and they grow fatter as they add cells around their tube-like bodies.

At the tip of each root, there is a small group of tough, dead, hard cells called the root cap. The root cap is the strongest part of the root tip, and its job is to push its way through the dirt to look for moisture and nutrients and protect the plant.

Dung beetle:

These creatures feed on and break up, or decompose, animal poo, adding nutrients to the soil. Dung beetles aerate and mix the soil by burrowing, and increase the organic matter content of the soil by burying dung. These changes improve the water holding capacity and nutrient availability of the soil, with associated benefits to plants. By burying dung, they also provide an important food source for decomposers, and reduce resources for the larvae of economic insect pests such as bushflies

Leafcutter ants:

Ants dig tunnels into the soil, letting in air and moving around decaying plants and animals, which add nutrients to the soil. Leaf-cutting ants modify soil fertility through two mechanisms. First, the building, enlargement, and maintenance of nests ants affect soil structure, porosity and density. Second, leafcutters collect and concentrate vegetal material inside their nests to maintain their fungus culture, the food for most of the colony. As a result of this process, ants generate a huge quantity of organic waste that is deposited in nest cavities or dumps on the soil surface.

Buttress roots:

Trees have shallow roots underground to quickly take in the water and nutrients in the topsoil. Most rainforest soil is very poor with all the nutrients available largely remaining at surface level. Because of this rainforest trees have very shallow roots. 

Some very tall trees have developed ways of obtaining much needed additional support by forming buttressed roots, which grow out from the base of the trunk sometimes as high as 15 ft above the ground. These extended roots also increase the area over which nutrients can be absorbed from the soil.

Forest floor:

Many leaves from the thick tree canopy fall to the dark forest floor and decay. The major compartments for the storage of organic matter and nutrients within systems are the living vegetation, forest floor, and soil. The forest floor serves as a bridge between the above ground living vegetation and the soil, and it is a crucial component in nutrient transfer through the biogeochemical cycle. Much of the energy and carbon fixed by forests is periodically added to the forest floor through litterfall, and a substantial portion of the nutrient requirements of forest ecosystems is supplied by decomposition of organic matter in the forest floor and soil surface. 

Autumn leaves:

As the weather gets cooler and the days get shorter in the fall, trees start to prepare for winter. Trees use sunlight to make a special layer or seal between each leaf and the branch it is connected to. Then the leaves fall easily to the ground, leaving the branches of the tree protected from the cold that will come in the winter and also helping the tree store up food!

Since leaves have water inside their cells, they can’t survive freezing temperatures, because the water would freeze and the leaves would die. When leaves fall to the ground, they eventually break down and provide nutrients for the soil, helping prepare for more plants to grow in the spring and also create a layer that helps the ground absorb water.


Earthworm burrows alter the physical structure of the soil. They open up small spaces, known as pores, within the soil. When earthworms are introduced to soils devoid of them, their burrowing can lead to increases in water infiltration rates of up to 10 times the original amount. This brings water and soluble nutrients down to plant roots. Burrowing also improves soil aeration (important for both plants and other organisms living in the soil) and enhances plant root penetration.

Tree roots:

Tree roots absorb nutrients and water from the soil. Large roots anchor the tree into the ground to prevent it from blowing over in the wind. Most roots live just 6-12 inches below ground and extend far beyond the width of the tree’s canopy. Cutting tree roots can cause stress to a tree and can leave it vulnerable to disease or insect attack. Roots need oxygen. By allowing soil to dry for several days between watering, oxygen can make its way to the roots. Avoid piling new soil or compacting the ground underneath the tree. This can suffocate the roots that absorb oxygen close to the surface. 


Cacti have shallow roots and thick stems, so they can collect and store water. Cacti can have many small, thin roots near the top of the soil. These roots take in water quickly after a rain. The same cactus may have one long, thick root called a taproot. The taproot grows deep in the soil. It can reach water when the soil on top is dry.

Deep roots:

Desert trees have very long roots to reach down and collect water from deep underground. There are several benefits to a deep root system rather than a large surface root system. A deep root system helps the plants stay grounded in the soil through harsh winds and other adverse conditions. And the plant is not dependent on rainfall to get water for survival.

Kangaroo rat:

When burrowing, animals break down large rocks, mix up the soil, and let air into it. Kangaroo rats play an important in the ecological communities in which they live. Specifically, they influence plant growth by feeding on and dispersing seeds and digging burrows in the soil. This contributes to the overall health of their ecosystem. They are also prey for numerous predators, including barn owls, burrowing owls, snakes, and coyotes. In order to help keep ecosystems healthy, we have worked with our partners to translocate kangaroo rats out of areas that are slated for development and into appropriate habitat on protected reserves.


The soil is usually deep and full of nutrients. This is because rotting grass roots help to hold the soil together and add nutrients for new plants. Plants compete for water. Grasslands occur in environments conducive to the growth of this plant cover but not to that of taller plants, particularly trees and shrubs. The factors preventing establishment of such taller, woody vegetation are varied.

Tropical rainforest:

The soil is very wet and many plants grow, so there is lots of humus to add nutrients to the soil. However, these nutrients are washed away by the constant rain, leaving shallow, acidic soil. Most tropical rainforest soils relatively poor in nutrients. Millions of years of weathering and torrential rains have washed most of the nutrients out of the soil. More recent volcanic soils, however, can be very fertile. Tropical rain forest soils contain less organic matter than temperate forests and most of the available nutrients are found in the living plant and animal material. Nutrients in the soil are often in forms that are not accessible by plants.

Constant warmth and moisture promote rapid decay of organic matter. When a tree dies in the rainforest, living organisms quickly absorb the nutrients before they have a chance to be washed away. When tropical forests are cut and burned, heavy rains can quickly wash the released nutrients away, leaving the soil even more impoverished. 

Temperate deciduous forest:

The soil is moist and full of nutrients from decaying plants and animals, especially in autumn. The deep roots of plants break up the bedrock, which adds minerals. Water often drains through steadily.
The soil of deciduous forests is classified as an alfisol or a brown forest soil.  It is very nutrient rich. This is caused by the large leaf fall during the fall seasons.  When the snow melts in the spring the leaves on the ground decompose and supply the nutrients that the plants need to grow.  This type of soil was considered the most fertile type of soil until the modern inventions allowed other types of soil to be modified.


The soil is very dry and few plants grow, so there is little humus. It is made up of boulders, pebbles, and sand, and is blown around by the wind. Any water drains through the sand easily. Deserts soils are generally of brown, light brown or reddish color. Due to arid conditions, leaching of soil is almost absent in the desert soils and thus evaporation is quite rapid.

Therefore, these soils are in general saline. Further in some low level areas, the salt content in the desert soil is really high. In fact, it is so high that common salt is obtained by evaporating the saline water collect from such areas.

However, salt content in some desert soils is not that high and thus in such cases they support vegetation in the sufficient availability of water. Moreover, in some areas land is rocky and is surrounded by gravel.


Picture Credit : Google