Soil Science

What is Soil Science and What are Branches of Soil Science

Soil Science is a branch of agriculture that deals with the upper and non-consolidated portion of earth as a medium for plant growth. Soil provides support, water, nutrients, and anchorage to the plants. Soil is not only important for the plants but is also a natural habitat for the soil biodiversity that in turn plays an important role to support plant growth by releasing and supplying nutrients, regulating nutrient cycles, and carbon sequestration.

The definition of soil is different for different disciplines such as engineering, agriculture, economists, and geologists point of view. But it is a valuable resource and must be protected to ensure quality life, and food security on a sustainable basis. Mining engineers and geologists may consider soil as debris or fragmented rocks that are covering the underlying rocks. While civil engineers can define soil as foundation material or earth for the construction of roads, and buildings. Whereas economists can consider the soil as land and they study soil as a resource for socio-economic conditions of different regions. Moreover, there are many soil science jobs and this subject matter is helpful to create livelihood for many people.

Components of Soil

Soil is a valuable resource and consists of mineral matter, organic matter, soil air, and soil water. Soil is a three-phase system and consists of organic matter and mineral matter in the solid phase, water containing gasses and salts in the liquid phases, and soil solution, and different gasses from different gas phases. Each of the phases is containing different constituents and therefore soil systems are having greater complexity. There are continuous and ongoing changes in the soil system, so the soil systems are never found in the equilibrium states.

  • Organic Matter in Soil

Soil organic matter can be defined as partially synthesized and partially decayed animal and plant residues. Organic material is decomposed in the soil by the action of soil microorganisms and causes the release of nutrients to the soil. Organic matter is considered a transitory constituent of soil and is being constantly renewed by the action of plant residues, animal residues, kitchen waste, and debris.

Organic matter affects all the properties of soil and helps to improve plant growth on a sustainable basis. Its optimal addition helps to improve the overall physical, chemical, and biological soil properties and thus helps to improve plant growth and development on a sustainable basis.

  • Soil Water

Soil water is one of the major components of the soil and is held in the soil pores. Soil water is critically important for nutrient uptake to the plants and thus it significantly contributes for the plant growth and development. Optimal moisture levels must be ensured in the soil to provide good conditions for plant growth and development. All the water present in the soil is not available for plant growth and some water is held in the soils that cannot be used by the plants. A significant portion of the water held in the soil remains in the form of thin film. Soil water also dissolves the nutrients and salts and makes soil solution and therefore it plays an important role in the nutrient provision and salt uptake to the plants. Nutrients are exchanged between soil solution and soil solids and thus it is retained in the soil solution and then is made available to the plants.

  • Soil Air

The part of soil solids or soil colloids that is not focused on by the water is occupied by the soil air and is helpful for the aeration of plant roots and soil biodiversity. A volume of soil is occupied by both air and water and the volume of air is inversely proportional to the soil water. Air contents in the soil are decreased by the increase of moisture or water contents in the soil.

Soil air contains numerous gases such as carbon dioxide, oxygen, and nitrogen and is different from the atmosphere in various perspectives. It contains less portion of oxygen and more concentration of carbon dioxide. Furthermore, it contains more moisture than the atmosphere and helps for plant growth and soil biodiversity. The composition and content of soil air are greatly determined by the relationships between soil and water.

Branches of Soil Science

Soil Chemistry

It is a branch of soil science that deals with the chemical properties of soil separates and chemical reactions taking place in the soil. It is essentially an important branch to deal with soil fertility, soil productivity, plant nutrition. Moreover, it also helps to control the application of synthetic chemicals such as pesticides, weedicides, insecticides, and fertilizers to ensure efficient use and control over different conditions.

Soil Biology

It is a branch of soil science that deals with soil biodiversity concerning plant growth, development, production, environmental protection, and regulation of changing climate. It deals with the inhabiting organisms in the soil and their activities, functions, and biology.

Soil Mineralogy

This branch of soil science is specifically concerned with the study of soil minerals, their release, and their contribution to the physics, chemistry, biology, fertility, and productivity of soils.

Soil Classification and Genesis

Soil genesis is the study of soil that deals with the disintegration, weathering, and decomposition of rocks and minerals that lead to the process of soil formation. Moreover, it is also concerned with studying the processes, and factors that cause soil formation and soil classification system. Whereas soil classification is specifically the systematic arrangement of soil to different categories and groups. This classification is based on characteristics of different soils and is helpful for the categorization of different types of soils for optimal land utilization. USDA soil classification chart is essentially helpful to provide details about soil systems and categories and is being adopted by different countries.

Soil Physics

Soil physics is concerned with studying the mechanical behavior of different soil masses and physical properties of soils with greater emphasis on specific states and transporting the matter such as energy and water in the soil.

Soil Fertility

Soil fertility is a branch of soil science and is concerned with studying the soil’s abilities for supplying macronutrients and micronutrients for plant growth, development, and production.

Soil Salinity

Soil salinity is a branch of soil science and is concerned with studying the excessive and soluble salts in the soil crust and soil solution. Moreover, it is also concerned with the management and reclamation strategies to improve overall soil health, soil structure, and production capability to improve environmental protection and food security.

Soil Survey

This branch of soil science is related to the systematic examination and study of soils in the lab and field, their classification, description, mapping, and specific interpretation according to suitability of specific group for management and production systems.

Soil Conservation

Soil conservation is a branch of soil science that deals with the conservation, and protection of soil resources from losses caused by the chemical and physical processes and factors. It also deals with the soil erosion management and protection of soil from chemical deterioration. Soil conservation techniques are specifically focused to combine different land use and management practices for safeguarding soil against destruction by human-induced and natural factors.

Soil Microbiology

Soil microbiology is a branch of soil science that deals with the study of microbial communities, their characteristics, and their roles concerning land reclamation, and soil fertility. It is especially important to deal with the nutrient, solubilisation, bio-availability, root nodulation, carbon sequestration, and disease management.


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