Soils are the loose organic or minerals found on the earth’s surface; they are about 25% air, 45% mineral, 25% water, and 5% organic matter (tiny living organisms, humus, and plant residue). Soil supports rooted plants in a natural environment. If you dig a massive hole into the ground, you will see that you would have cut through various layers of soil each with distinct color and texture. Looking at the layers from a distance gives the soil profile.
What is a Soil Profile
If you create a massive hole, about 50-100 ft vertically downwards into the ground, you will see that you would have cut through various layers of soil types. Looking at the layers from a distance gives one a cross-section view of the ground and the kind of soils and rocks. This cross-section view is known as a Soil Profile. The profile comprises layers running parallel to the surface that are called Soil Horizons.
Each horizon may be slightly or drastically different from the other above or below it. Each horizon tells a tale about it’s constituents, texture, age, and characteristics of that layer. Consequently, most soils have three major horizons, namely A Horizon, B Horizon, and C Horizon. Besides these three, there are also the O, E, and R horizons.
Soil Profile – The O-Horizon
The O horizon is very common on many surfaces with many vegetative covers. It comprises of organic materials such as twigs, and fallen trees, dead leaves and surface organisms. This horizon has about 20% organic matter. Additionally, it is possible to see various decomposition levels occurring here (minimal, moderately, highly, and wholly decomposed organic matter).
This layer is often black or dark brown because of the organic content. It is the layer in which the roots of small grass are found. The uppermost horizon of the soil profile call O-horizon or litter zone. It is usually not present in the soils of the desert, grassland and cultivated filed and found only in soils of forests.
Soil Profile – A-Horizon:
The A-horizon may be seen when there is no O horizon. It is usually known as the topsoil. It is the top layer of soil for many agricultural lands and grasslands. They are made of silt, sand, and clay with high organic matter. A-Horizon is most vulnerable to water and wind erosion. It is also known as the root zone. it contains under-composed, partially decomposed and completely decomposed humus from upper to lower sides.
This horizon is usually sandy, and several inches thick. This is the layer of maximum biological activity in the soil. It contains the bulk of the organic matter. Hence it is of considerable importance to agricultural crops and vegetation. Reckless deforestation over the years has led to a considerable loss of topsoil.
Soil Profile – The E-Horizon:
E horizon is lighter in color, often below the O horizon and A horizon. It is usually rich in nutrients leached from the top A horizon and O horizon. Additionally, t has a lower clay content. Additionally, it is common in forested lands or areas with high-quality O horizon and A horizon.
Soil Profile – The B-Horizon:
B-horizon has some similarities with the E-horizon. This horizon is formed below the O, A, and E horizons and may contain high silicate clay, iron, aluminum, and carbonates. It is called the illuviation zone because of the accumulation of minerals. It is the layer in which the roots of giant trees end and is also known as sub-soil. The next layer is the B-horizon. It receives minerals, organic matter, salts, or clay particles leached from the topsoil.
Soil Profile – The C-Horizon:
C horizon lacks all the properties of the previous layers lying above it. It has mainly composed of broken bedrock and no organic material. Additionally, it has cemented sediment and geologic material. There is little activity, although additions and losses of soluble materials may occur. Consequently, this layer is also known as saprolite. This zone comprises of weathered parent rocks from which the soil originates. It is coloured and virtually lacking in organic material. It is often coarse-grained and pebbly in texture.
Soil Profile – The R-Horizon:
The R horizon is the bedrock material, compacted and cemented by the weight of the overlying horizons. It is the un-weathered parent material. This is the parent rock itself in unaltered position. Subsequently, the rock types found here include granite, basalt, and limestone.
Importance of Soil Profile
Soil categorization takes place on the basis of their texture, color, composition, profile, texture, or structure. Each type of soil forms differently. They can be found on the earth’s immediate surface, mid and deep under the cover. Additionally, the soil on the surface is usually exposed to direct climatic and environmental factors and washed away by water. Additionally, they can be easily blown away by the wind or even broken down by temperature changes, human and animal activity.
However, soil can be categorized based on the components.
One important subject that many soil scientists and farmers lookout for is soil chemistry. Soil chemistry includes:
- Soil pH (the soil’s acidity).
- Organic content.
- Nutrient level.
- The chemical composition of the minerals found in the soil.
determine the soil chemistry.
The following factors determine the soil chemistry
- The types of plants growing in them,
- the geographic location of the soils,
- Exposure of soil to environmental factors such as water and air.
Soils are essential for life as they
- provide the medium for plant growth,
- offer habitat for several insects and other organisms,
- act as a filtration system for surface water, carbon storage, and maintenance of atmospheric gases.
Soil Profile Offer Medium for plant growth:
- They support roots and keep them upright for development.
- Soil provides plants with essential minerals and nutrients.
- They provide air for gaseous exchange between roots and the atmosphere.
- Soils protect plants from soil erosion and other destructive physical, chemical, and biological activities.
- They hold water (moisture) and maintain adequate aeration.
Soil Profile Offer Habitat for insects and other organisms:
- Microbes and insects live in the soils and depend on soils for food and air.
- Soils are homes to various organisms such as termites and worms. Subsequently, they provide the needed air and moisture for the breakdown of organic matter.
- They provide a home for different lifeforms such as insects to lay and hatch eggs and rodents to give birth to new offspring.
Soil Profile Acts As Filter for surface water:
After snowmelts and rainfall, water flows on the earth’s surface and reaches water bodies. Chemicals, dust, and other contaminants gets filtered out, as the water continues downwards through the several layers in the ground. Consequently, aquifers are one of the purest water sources. Additionally, filtered water provides plants with clean and unpolluted water required for growth.
Soil Profile for Carbon storage
Soils help in regulating atmospheric Carbon dioxide as they act as carbon storage. During humification, some organic matter breakdown does not occur completely, especially in soils like peat, due to its high water and acid content.
Soil Profile for Maintaining atmospheric gases
Globally, soil contains about twice as much carbon as the atmosphere and nearly three times as vegetation. Consequently, it results in the accumulation of organic matter in the soil, high in carbon content. Phosphorus, Nitrogen, and many other nutrients get stored and transformed in the soil.
Soil Profile Descriptions
Soil profile descriptions are primary data in all soil surveys. They provide a significant part of the information required for the correlation and classification of the soils of an area. They are essential for interpreting soils and coordinating the interpretations across state and regional boundaries. The soil descriptions and the soil map are the parts of a published survey having the most extended useful life.
Good field descriptions include:
- observed external attributes such as landform and characteristics of a slope;
- inferred attributes such as the origin of soil parent material and the annual sequence of soil-water states;
- observed internal properties , such as horizon thickness, color, texture, structure, and consistency;
- inferred genetic attributes , such as horizon designations and parent material;
- inferred soil drainage class;
- classification in the lowest feasible category;
- location of the site relative to geographic markers and in terms of landscape position;
- plant cover or use of the site;
- date, time of day, and weather conditions; and
- name of the describer.
Each of the seven soil horizons has a unique mineral content and variation in texture, but all contribute to the health of the soil of an area and how well plants grow overtop. The elements in soil horizons can provide knowledge more about the soil. Subsequently, farmers can use it to grow healthier crops. The analysis of soil is easy. Consequently, it is possible to extract and examine a soil profile right at home. However, the deeper layers of soil are harder to reach and are not necessary for the soil analysis of small areas of land. The most useful information comes from the top soil layers, such as horizon A and horizon O.
Soil profile are informative as they are a collection of everything that has gathered in a specific area of soil since its original formation. Of course, minerals that were present in the original, parent material may not exist so much now, but if they do, you could find them at the deepest point in the soil. Formation of soil takes several years – it is an untapped database until someone digs it up.