Glossary
Fragipan - A dense, natural subsurface layer of hard soil with relatively slow permeability to water, mostly because of its extreme density or compactness rather than its high clay content or cementation.
Alluvium - (from the Latin, alluvius, from alluere, "to wash against") is soil or sediments deposited by a river or other running water. Alluvium is typically made up of a variety of materials, including fine particles of silt and clay and larger particles of sand and gravel. Flowing water associated with glaciers may also deposit alluvium, but deposits directly from ice are glacial till. A river is continually picking up and dropping solid particles of rock and soil from its bed throughout its length. Where the river flow is fast, more particles are picked up than dropped. Where the river flow is slow, more particles are dropped than picked up. Areas where more particles are dropped are called alluvial or flood plains, and the dropped particles are called alluvium. Even small streams make alluvial deposits, but it is in the flood plains and deltas of large rivers that large, geologically-significant alluvial deposits are found.
Loam is soil composed of sand, silt, and clay in relatively even concentration. Loams are gritty, plastic when moist, and retain water easily, yet they drain well where the topography allows. They generally contain more nutrients than sandy soils. In addition to the term loam, different names are given to soils with slightly different proportions of sand, silt, and clay: sandy loam, silty loam, clay loam, sandy clay loam, silty clay loam. A "loamy" soil feels mellow and is easy to work over a wide range of moisture conditions. A soil dominated by one or two of the three particle size groups can behave like loam if it has a strong granular structure (promoted by a high content of organic matter). However, a soil that meets the textural definition of loam can become unlike loamy earth if it is compacted, depleted of organic matter, or has dispersive clay in its fine-earth fraction.
Organic matter is the plant and animal residue in the soil at various stages of decomposition. In the data, the estimated content of organic matter is expressed as a percentage, by weight, of the soil material that is less than 2mm in diameter. The content of organic matter in a soil can be maintained by returning crop residue to the soil. Organic matter has a positive effect on available water capacity, water infiltration, soil organism activity and tilth. It is a source of nitrogen and other nutrients for crops and soil organisms.
Tilth - arable land that is worked by plowing and sowing and raising crops, or the state of aggregation of soil and its condition for supporting plant growth.
Sand - Mineral soil particles that are between 0.05 millimeters and 2 millimeters in diameter, with percentages show in weight of materials less than 2 millimeters in diameter.
Silt - Mineral soil particles that are 0.002 to 0.05 millimeter in diameter, with percentages shown in weight of materials less than 2 millimeters in diameter. Silt is produced by the mechanical weathering of rock (glaciers, wind, water) and is primarily composed of quartz and feldspar.
Clay - Mineral soil particles that are less than .002 millimeter in diameter, with percentages shown in weight of materials less than 2 millimeters in diameter. Clay is produced by the chemical weathering of rock, generally carbolic acid, and is primarily composed of hydrous aluminium phyllosilicate minerals.
Channery - A descriptive term used for thin and flat limestone, sandstone, or schist fragments up to 15 cm (6 inches) in length.
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