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- Soil organic matter is a complex mixture of organic compounds such as plant residues, microbial products and rhizosphere inputs in various stages of decomposition (Kögel-Knabner and Rumpel, 2018; Lehmann and Kleber, 2015).
www.sciencedirect.com/topics/agricultural-and-biological-sciences/soil-organic-matter
Soil organic matter (SOM) can be defined as organic materials found in soil that are, or have been, part of living organisms. It is a continuum of materials at various stages of transformation due to biotic and abiotic processes.
- Soil Quality
Soil quality – A critical review. Else K. Bünemann, ......
- Microbial Biomass
Soil Biology & Biochemistry Citation Classic IX. Richard G....
- Soil Structure
Global applications of the Visual Evaluation of Soil...
- Soil Organic Matter
Soil organic matter (SOM) is commonly defined as the organic...
- Soil Quality
Jun 16, 2022 · Soil organic matter comes from the organic material from plants (e.g. leaves and woody materials), animals (e.g. decaying components), and microorganisms. The presence of organic matter in the soil is essential as a source of nutrients for crops and other garden plants.
soil organic matter - Plant, animal, and microbial residues, in various states of decomposition. soil texture - The percentages of sand, silt, and clay particles in a soil.
Soil organic matter is the key to building and maintaining healthy soils because it has such great positive influences on essentially all soil properties—aggregation, nutrient availability, soil tilth and water availability, biological diversity and so on— helping to grow healthier plants.
- 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
Soil organic matter (SOM) refers to the organic component of soil, consisting mainly of decomposed plant and animal material, microbial biomass, and organic substances that enhance soil structure, fertility, and overall health.
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Where does organic matter come from?
Soil organic matter (SOM) is commonly defined as the organic fraction of the soil exclusive of undecayed plant and animal residues. Sometimes, in a broader definition, SOM encompasses the totality of organic material (living and nonliving) present in soils, including thus, living microorganisms and undecayed residues.
