Soil Science: Definition, Concept and Soil

What is Soil Science?

Definition: Soil science is the study of soil as a natural resource, including its formation, classification, mapping, and properties (physical, chemical, biological, and fertility) in relation to crop production.

Concept: Soil science is a multidisciplinary field that draws upon knowledge from geology, biology, chemistry, physics, and other sciences to understand the complex nature of soil. It aims to: -  

• Characterize soils: Identify and classify different soil types based on their properties.  
• Understand soil formation: Investigate the processes that create and shape soils over time.
• Assess soil quality: Evaluate the suitability of soils for various uses, such as agriculture, forestry, and construction.  
• Develop sustainable soil management practices: Promote practices that maintain and improve soil health and productivity.

Approaches to Soil Science

Pedological Approach: Focuses on soil as a natural body, its formation, and classification.

Edaphological Approach: Views soil as a medium for plant growth and crop production.

What is Soil?

Definition: Soil is a dynamic natural body composed of mineral and organic matter, water, and air. It is the uppermost layer of the Earth's crust that supports plant life.  

Soil is the loose surface material on the Earth derived from rocks and minerals through weathering. It acts as a medium for plant growth and life. Various definitions highlight its roles in providing nutrients, supporting plant roots, and maintaining ecological balance.

Concepts of soil : 

Soil is more than just dirt. It is a complex ecosystem teeming with life, including microorganisms, insects, and plant roots. The composition and properties of soil vary greatly depending on factors like climate, parent material, topography, organisms, and time.  

Scientists/Researchers ; who Contributed to Soil or Soil Science

• Vasily Dokuchaev (1846-1903): Considered the "father of soil science," he developed the concept of soil as a natural body influenced by climate, organisms, topography, parent material, and time (the five soil-forming factors).  

  

  Fig 1: Vasily V. Dokuchaev (1846-1903)

  
  
• Eugene W. Hilgard (1833-1916): A pioneer in American soil science, he conducted extensive research on soil classification and mapping.   
• Curtis F. Marbut (1863-1935): A leading figure in soil survey and classification, he developed the first comprehensive soil classification system for the United States.   
• Hans Jenny (1904-1998): A renowned soil scientist who formulated the "State Factor Equation," a mathematical model that describes soil formation.   

 Branches of Soil Science

• Pedology: The study of soil formation, classification, and mapping.  
• Edaphology: The study of how soils interact with living things, especially plants.  
• Soil physics: The study of the physical properties of soil, such as texture, structure, water-holding capacity, and aeration.  
• Soil chemistry: The study of the chemical composition and reactions of soil, including nutrient availability and pollution.  
• Soil biology: The study of the living organisms in soil, such as microorganisms, insects, and plant roots.  
• Soil fertility: The study of soil's ability to supply nutrients for plant growth.  
• Soil conservation: The study of methods to protect soil from erosion and degradation.  

Functions of Soil

• Supports plant growth: Provides essential nutrients, water, and physical support for plant roots.  
• Filters water: Removes pollutants and impurities from water as it percolates through the soil.  
• Stores carbon: Acts as a significant carbon sink, helping to regulate the Earth's climate.  
• Provides habitat: Supports a diverse range of organisms, including microorganisms, insects, and small animals.  
• Recycles nutrients: Breaks down organic matter and releases nutrients back into the ecosystem.   
• Food production.
• Grazing land.
• Forest products.
• Infrastructure support.
• Cleansing and repository functions.

Components of Soil

Solid Space (50%)
• Mineral Matter (45%): Derived from rocks and minerals.
• Organic Matter (5%): Decomposed plant and animal residues.

Pore Space (50%)
• Water (25%): Acts as a nutrient carrier.
• Air (25%): Essential for root and microbial respiration.

Fig 2: Components of Soil

Soil Profile and Horizons

Soil profiles consist of distinct layers (horizons) with specific characteristics:

O-Horizon: Organic layer.

A-Horizon: Topsoil with humified organic matter.

E-Horizon: Zone of leaching.

B-Horizon: Zone of accumulation.

C-Horizon: Parent material.

R-Layer: Bedrock.

Fig 3: Soil Profile (Horizon)

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Some important books and references materials for students to study soil science in depth 

1. General Soil Science:

• Brady, N.C., & Weil, R.R. (2016). The nature and properties of soils. Pearson Education.

• Lal, R. (Ed.). (2006). Encyclopedia of soil science. 2nd ed. Marcel Dekker.

2. Soil Formation and Classification:

• Jenny, H. (1941). Factors of soil formation. McGraw-Hill.

• Soil Survey Staff. (2014). Soil taxonomy: A basic system of soil classification for making and interpreting soil surveys. 3rd ed. U.S. Department of Agriculture, Natural Resources Conservation Service.

3. Soil Physics:

• Hillel, D. (2004). Environmental soil physics. Academic Press.

4. Soil Chemistry:

• Sparks, D.L. (2003). Soil physical chemistry. 3rd ed. Academic Press.

5. Soil Biology:

• Paul, E.A., & Clark, F.E. (1996). Soil microbiology and biochemistry. 3rd ed. Academic Press.

6. Soil Fertility and Management:

• Havlin, J.L. (2014). Soil fertility and fertilizers: An introduction to nutrient management. 8th ed. Pearson Education.

7. Soil Conservation:

• Lal, R. (Ed.). (2006). Soil erosion research methods. 2nd ed. CRC Press. 

Soil science is a critical field that helps us understand and manage this vital natural resource. By studying soil, we can improve agricultural productivity, protect water quality, mitigate climate change, and maintain a healthy environment.

References : 

1. https://www.scholarsresearchlibrary.com/articles/soil-science-role-in-agriculture-significance-and-applications-102399.html#:~:text=The%20study%20of%20soils%2C%20known,interactions%20occurring%20beneath%20our%20feet.

(Retrieved on 2024.12.24)

2. https://www.nrcs.usda.gov/resources/education-and-teaching-materials/soil-facts#:~:text=Soil%20science%20is%20the%20science,%2C%20classification%2C%20and%20mapping%3B%20physical

(Retrieved on 2024.12.24)

3. https://handbook.unimelb.edu.au/2023/subjects/agri20038

(Retrieved on 2024.12.24)

4. https://en.wikipedia.org/wiki/Soil_science#:~:text=Soil%20science%20is%20the%20study,and%20mapping%3B%20physical%2C%20chemical%2C

(Retrieved on 2024.12.24)

5. http://www.edafologia.net/comun/congres/cartart.htm#:~:text=Land%20evaluation%20is%20an%20applied,derive%20maximum%20benefits%20with%20minimum

(Retrieved on 2024.12.24)