Different People Have Different Concepts of Soil
Soil is a concept that varies widely among individuals, influenced by their perspectives and uses For farmers, soil is synonymous with land, essential for crop growth, focusing primarily on the root zone In contrast, potters equate mud and clay with soil, utilizing it for pottery Different professionals also interpret soil uniquely; geologists see it as the biologically modified upper layer of regolith formed through weathering, while geographers define it as a thin, discontinuous layer of loose material on the earth's surface Engineers regard soil as any loose, unconsolidated earth material that serves as a foundation for structures, without differentiating it from other loose materials like sediment.
Soil is a unique three-dimensional body that stands apart from other natural materials, characterized by its unconsolidated nature on the Earth's surface It has developed through intricate pedogenic processes, combining mineral and organic matter to form distinct morphological, physical, chemical, and biological traits This evolution enables soil to support vegetation and various life forms, making it an ecosystem in its own right, while also being an integral component of larger terrestrial ecosystems.
1.2 There Are Many Different De fi nitions of Soil
Different scientists have de fi ned soil in different ways Some of these de fi nitions are given below to show the evolution of the modern concepts of soil.
Soils are formed from the upper layers of rocks that have been altered by natural processes involving water, air, and both living and dead organisms This interaction influences the composition, structure, and color of the soil In the absence of these natural conditions, what exists are not true soils, but rather artificial mixtures of rock.
Soil is the top layer of the earth's crust, formed from weathered rock fragments and enriched by the remains of plants and animals This vital resource undergoes chemical changes, playing a crucial role in supporting life and ecosystems.
Soil is a loose and friable material that provides plants with a foundation for their roots, essential nutrients, and the necessary conditions for growth.
Soil is a natural entity composed of mineral and organic materials, organized into distinct layers known as horizons It varies in depth and differs from the underlying material in its morphology, physical structure, chemical properties, and biological characteristics.
Soil is a collection of natural bodies occupying a portion of the earth surface that supports plant growth and that has properties
2 1 Concepts of Soil due to the integrated effect of climate and vegetation acting upon parent material, as conditioned by relief, over a period of time
Soil is a natural entity made up of minerals, organic matter, liquids, and gases found on the Earth's surface It features distinct layers, known as horizons, which develop through processes of addition, loss, transfer, and transformation of energy and matter Additionally, soil is essential for supporting rooted plants in their natural habitats.
1.3 All Loose Materials on the Surface of the Earth Are Not Soils
Loose materials on the Earth's surface, such as desert sands, sandy beaches, and riverbed sediments, are not classified as soils despite their limited ability to support plant growth These materials typically lack organic matter and available water, which are essential for soil formation Sands consist of discrete particles rather than aggregated structures found in true soils While some of these materials may contain organic matter, they do not exhibit profile development characteristic of soils Over time and under favorable conditions, these parent materials can evolve into actual soils through the process of pedogenesis.
Materials above solid bedrock that are less than 10 cm thick, whether mineral or organic, do not qualify as soils Additionally, unconsolidated materials submerged under more than 60 cm of water year-round, as well as organic materials thinner than this threshold, are also excluded from the definition of soil.
Soils are defined as lacking when there is over 40 cm of water covering their surface In coastal regions, some soils may have water depths of up to 60 cm during low tide, while inland areas may experience similar conditions during the driest times of the year Subaqueous soils, which consist of soil materials, mud, or sediments found underwater, are located at depths of less than 2.5 meters.
1.4 Soil Is Not Land Itself; It Is a Part of Land
Land refers to the non-water areas of the Earth's surface, while soil is a thin layer found on some of this land Understanding the distinction between land and soil is essential for environmental studies and land management.
Some areas of land lack soil entirely, featuring rocky surfaces, desert sands, or glaciers over solid rock Fresh sediment deposits may exist but are not yet classified as soil While soil has a defined lower limit above its parent material, land does not; digging deeper into the land reveals no soil Vegetation thrives only on land with soil, and the visible portion of land is referred to as the landscape Within this landscape, areas with similar slopes, vegetation, or cropping potential are categorized as land Different soils can exist in various positions on the same land Although both land and soil are natural resources, only land is typically owned as property, and its uses can vary based on soil and other characteristics.
Soil is a natural entity that has evolved over time through natural processes from parent materials, which can be either organic or inorganic While over 99% of soils are derived from inorganic materials—specifically the disintegration and decomposition of rocks and minerals—some soils originate from organic materials, typically accumulated under wet conditions The collective processes of weathering lead to the breakdown of these parent materials, allowing organisms such as plants, animals, and microbes to contribute organic matter Over an extended period, climate and topography influence these materials, transforming them into soil through a process known as pedogenesis.
So, the soil is a natural body Brady and Weil ( 2002 ) says,
“Soil is a natural body in the same sense as that a mountain, a lake or a valley is.”
1.6 Soil Is a Three-Dimensional Body
Soil is a natural unit characterized by distinct physical, chemical, and biological properties, which can vary significantly across a landscape As one moves laterally, different soils with unique properties can be encountered Additionally, soil exists within a defined vertical range, with the upper layer consisting of regolith, which includes unconsolidated and loose materials above bedrock Thus, soil encompasses three dimensions, highlighting its complexity and variability.
3 1.9 Soil Is a Recycler of Materials two laterals and one vertical, that is, length, width, and depth
A soil has a volume too The smallest volume of a soil having similar characteristics throughout the lateral dimensions is called a pedon (Soil Survey Staff 1975, 1999 ) Simonson
( 1978 ) de fi ned pedon as the smallest effective unit of soil
A pedon is an arbitrary unit used for soil examination and sampling in the field, typically covering an area of 1–10 m² and often taking a hexagonal shape.