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Soil and Water Assessment Tool
The Soil and Water Assessment Tool, or SWAT, is a public-domain watershed model that predicts how management decisions affect water, sediment, nutrient, and pesticide yields.
Soil and Water Conservation Society
Soil and Water Conservation Society (SWCS), international nonprofit for conservation professionals founded as the Soil Conservation Society of America (first meeting 1946), based in Ankeny, Iowa, publisher of the Journal of Soil and Water Conservation.
Soil augering
Soil augering is a field method of obtaining soil samples from depth by rotating a boring tool into the ground without excavating a pit, used widely in soil mapping.
Soil catena
A soil catena is a sequence of related soils along a hillslope, from hilltop to valley floor, that share parent material and age but differ because of drainage.
Soil classification
Soil classification is the systematic grouping of soils into named categories based on measurable properties, dominated by USDA Soil Taxonomy with 12 orders and the international World Reference Base.
Soil compaction
Soil compaction is the pressing together of soil particles under surface pressure, reducing pore space and increasing bulk density; in farming it degrades soil, while construction induces it deliberately.
Soil conservation
Soil conservation: practices preventing soil erosion, compaction, salinization, and fertility loss through cover crops, conservation tillage, terraces, windbreaks, and hedgerows; FAO's 2026 assessment finds erosion the worst threat and adoption lagging.
Soil contamination
Soil contamination, also known as soil pollution, is the presence of chemicals in soil above natural background levels, posing risks to human health, ecosystems, food, and water.
Soil erosion
Soil erosion is the removal of the nutrient-rich surface soil by water and wind; accelerated erosion from human activity degrades farmland and fills rivers and reservoirs with sediment.
Soil fertility
Soil fertility: a soil's capacity to supply essential plant nutrients, governed by pH, cation exchange capacity, texture, and soil organic matter. Also called soil quality/health component; assessed via minimum data sets, managed through integrated nutrient management.
Soil formation
Soil formation (pedogenesis) is the production of soil from parent material through five factors: climate, organisms, relief, parent material, and time (CLORPT), over hundreds to thousands of years.
Soil horizon
A soil horizon is a layer of soil roughly parallel to the surface that differs from adjacent layers in color, texture, and structure, forming the soil profile.
Soil improvement
Soil improvement: agricultural and geotechnical practices, from organic amendments, cover crops, and salinity reclamation to cement, MICP, and geopolymer stabilization, used to restore degraded soils and strengthen ground.
Soil incubation experiments
A soil incubation experiment is a laboratory method in which soil is held under controlled temperature and moisture while carbon or nitrogen mineralization is measured.
Soil liquefaction
Soil liquefaction is a phenomenon where saturated, loose granular soils, like sands and silts, temporarily lose strength and behave as viscous fluids under rapid or static loading.
Soil mechanics
Soil mechanics is the branch of applied mechanics that predicts the performance of earth structures and foundations from soil properties, founded by Karl Terzaghi in 1925.
Soil moisture
Soil moisture, also called soil water content, is the amount of water held in the soil, a driver of soil processes and a key variable in agriculture, hydrology, and meteorology.
Soil nailing
Soil nailing is a geotechnical construction method that reinforces in-place soil with steel bars drilled and grouted into a slope or excavation face, stabilizing cuts built from the top down.
Soil pH
Soil pH, also known as soil acidity or soil reaction, measures how acid or alkaline a soil is and controls which nutrients plants can take up.
Soil resistivity
Soil resistivity is the measure of how strongly soil resists conducting electrical current, a basic parameter for grounding, lightning protection, and corrosion control of buried structures.
Soil salinity
Soil salinity, or the accumulation of salts in saline soils, impairs plant growth on over 1,381 million hectares worldwide; irrigation without leaching and drainage is a leading cause.
Soil science
Soil science is the study of soils as a natural resource, covering how they form, their classification and mapping, and their physical, chemical, and biological properties.
Soil sealing
Soil sealing is the covering of ground by impermeable materials such as asphalt or concrete, considered a major and nearly irreversible cause of soil degradation in the European Union.
Soil solarization
Soil solarization: nonchemical disinfestation of moist soil under transparent plastic film for 4-6 weeks in hot seasons, heating soil 2-15 C to kill pathogens, nematodes, and weed seeds; often combined with amendments, steam, or fumigants.
Soil stabilization
Soil stabilization is a geotechnical method that improves the strength and durability of weak soils by blending soil gradations or mixing in additives like lime, cement, fly ash, or bitumen.
Soil survey
A soil survey is a field method in which soils across a landscape are examined, mapped, and classified to predict their suitability and limitations for land uses.
Soil texture
Soil texture, also called soil texture classification, is the relative proportion by weight of sand, silt, and clay in a soil, read on the USDA textural triangle.
Soil type
A soil type is a class of soil defined by properties such as texture, color, and structure, classified in systems like USDA Soil Taxonomy and the WRB.
Soil vapor extraction
Soil vapor extraction (SVE) is an in situ remediation technology that applies a vacuum to wells to draw volatile organic compounds out of unsaturated soil for treatment.
Soil water retention curve
The soil water retention curve, or soil water characteristic curve, relates the water a soil holds to its matric potential, a key property for irrigation and drainage design.