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Apr 27, 2024 · Soil degradation refers to deterioration in the quality of the soil and the resultant reduction in its capacity to produce. Soils are degraded primarily by erosion, compaction, and salinization. Such processes often arise from poor soil management during agricultural activities.
- Overview
- Soil horizons
- Pedons and polypedons
Soil is the biologically active and porous medium that has developed in the uppermost layer of Earth’s crust. It serves as the reservoir of water and nutrients and a medium for the filtration and breakdown of injurious wastes. It also helps in the cycling of carbon and other elements through the global ecosystem.
What are the grain sizes in soil?
The grain size of soil particles are categorized into three groups: clay, silt, and sand. Clay measures less than 0.002 mm (0.0008 inch) in diameter, silt is between 0.002 mm (0.0008 inch) and 0.05 mm (0.002 inch), and sand is between 0.05 mm (0.002 inch) and 2 mm (0.08 inch).
What are the five factors of soil formation?
The evolution of soils and their properties is called soil formation, and according to pedologists, five fundamental soil formation processes influence soil properties. These five “state factors” are parent material, topography, climate, organisms, and time.
What are the layers of soil?
Soils differ widely in their properties because of geologic and climatic variation over distance and time. Even a simple property, such as the soil thickness, can range from a few centimetres to many metres, depending on the intensity and duration of weathering, episodes of soil deposition and erosion, and the patterns of landscape evolution. Nevertheless, in spite of this variability, soils have a unique structural characteristic that distinguishes them from mere earth materials and serves as a basis for their classification: a vertical sequence of layers produced by the combined actions of percolating waters and living organisms.
These layers are called horizons, and the full vertical sequence of horizons constitutes the soil profile (see the figure). Soil horizons are defined by features that reflect soil-forming processes. For instance, the uppermost soil layer (not including surface litter) is termed the A horizon. This is a weathered layer that contains an accumulation of humus (decomposed, dark-coloured, carbon-rich matter) and microbial biomass that is mixed with small-grained minerals to form aggregate structures.
Below A lies the B horizon. In mature soils this layer is characterized by an accumulation of clay (small particles less than 0.002 mm [0.00008 inch] in diameter) that has either been deposited out of percolating waters or precipitated by chemical processes involving dissolved products of weathering. Clay endows B horizons with an array of diverse structural features (blocks, columns, and prisms) formed from small clay particles that can be linked together in various configurations as the horizon evolves.
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Below the A and B horizons is the C horizon, a zone of little or no humus accumulation or soil structure development. The C horizon often is composed of unconsolidated parent material from which the A and B horizons have formed. It lacks the characteristic features of the A and B horizons and may be either relatively unweathered or deeply weathered. At some depth below the A, B, and C horizons lies consolidated rock, which makes up the R horizon.
Soils are natural elements of weathered landscapes whose properties may vary spatially. For scientific study, however, it is useful to think of soils as unions of modules known as pedons. A pedon is the smallest element of landscape that can be called soil. Its depth limit is the somewhat arbitrary boundary between soil and “not soil” (e.g., bedrock). Its lateral dimensions must be large enough to permit a study of any horizons present—in general, an area from 1 to 10 square metres (10 to 100 square feet), taking into account that a horizon may be variable in thickness or even discontinuous. Wherever horizons are cyclic and recur at intervals of 2 to 7 metres (7 to 23 feet), the pedon includes one-half the cycle. Thus, each pedon includes the range of horizon variability that occurs within small areas. Wherever the cycle is less than 2 metres, or wherever all horizons are continuous and of uniform thickness, the pedon has an area of 1 square metre.
Soils are encountered on the landscape as groups of similar pedons, called polypedons, that contain sufficient area to qualify as a taxonomic unit. Polypedons are bounded from below by “not soil” and laterally by pedons of dissimilar characteristics.
- Garrison Sposito
For soil science students and soil survey practitioners who want more than a simple definition, this glossary offers additional information for a deeper understanding. A wide array of terms are included. Some are terms from Soil Taxonomy that have specific technical definitions and criteria. Examples include . andic soil properties ...
Soil erosion is a continuous process that occurs either slowly or at an alarming rate. It results in a continuous loss of topsoil, ecological degradation, soil collapse, etc. Let us have a detailed look at the causes, effects and prevention of soil erosion.
- 58 min
- Soil erosion is the process of wearing away of the surface layer, or topsoil, by the transportation of the surface particles under the mechanical a...
- Yes, soil erosion removes the fertile top layer of the soil. This exposes the hard rocky lower layers which are less fertile and have less humus, t...
- The removal and transportation of the top layer of soil from its original position to another place, under the effect of strong winds and fast runn...
- Top soil is the upper fertile biologically active layer of soil which is rich in minerals, organic matter, and microorganisms (bacteria, fungi, ear...
May 5, 2024 · A biome is a geographical region characterized by specific climate conditions, vegetation, and animal life. Each biome consists of multiple ecosystems and habitats. The main factors that define a biome include temperature, precipitation, humidity, altitude, and soil type, all shaping the environment and determining the organisms that thrive there.
A typical soil has a soil profile consisting of four horizons, which are designated: O, A, B and C. The O horizon is the top layer at the earth's surface. It consists of surface litter, such as fallen leaves (duff), sticks and other plant material, animal waste and dead organisms.
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Jul 10, 2023 · The soil is one of the Earth’s most important ecosystems. (For a brief brush-up on ecology and ecosystems, see the background section below.) Every handful of soil contains literally billions of organisms—almost all of them microorganisms, too small to be seen with the unaided eye.
