| A | B |
|---|
| Alluvium | A soil parent material, such as sand silt or clay, deposited on land by streams |
| Clay | A soil particle that is less than 0.002 mm in diameter. Clay particles are so fine they have more surface area for reaction. They hold a lot of nutrients and water in the soil. A clay soil is a soil that has more than 40% clay, less than 45% sand and less than 40% silt. |
| Claypan | A dense, compact, slowly permeable layer in the subsoil having a much higher clay content than the overlying material, from which it is separated by a sharply defined boundary. Claypans are usually hard when dry, and plastic and sticky when wet |
| Ecoregion | Represents areas with similar biotic and abiotic characteristics which determine the resource potential and likely responses to natural and man-made disturbances. Characteristics such as climate, topography, geology, soils, and natural vegetation define an ecoregion. They determine the type of land cover that can exist and influence the range of land use practices that are possible. |
| Horizon | see Soil horizons |
| Landform | Any recognizable form or feature on the earth’s surface, having a characteristic shape and produced by natural causes. |
| Landscapes | A wide view of the land from above that shows many different combinations of land shapes and features. Landscape is a collection of these natural landforms. |
| Loess | A loosely compacted deposit of windblown silt-sized sediment. Also a soil parent material transported to and deposited in current location by wind. |
| NoTill | Farming that does not use a plow to turn over the top 15-20 cm (6-8 inches) surface of soil (topsoil) before planting seeds. Organic matter: Material derived from the decay of plants and animals. Always contains compounds of carbon and hydrogen. |
| Physiographicprovince | Are broad-scale subdivisions based on terrain texture, rock type, and geologic structure and history. |
| PrimeFarmland | Land that has the best combination of physical and chemical characteristics for producing food, feed, forage, fi-ber, and oilseed crops and is also available for these uses |
| Sand | A soil particle between 0.05 and 2.0 mm in diameter. Sand is also used to describe soil texture according to the soil textural triangle, for example, loamy sand. |
| Silt | A soil particle between 0.002 and 0.05 mm diameter. It is also used to describe a soil textural class. |
| SoilHorizon | The sequence of natural layers, or horizons, in a soil. It extends from the surface downward to unconsolidated material. Most soils have three major horizons, called the surface horizon, the subsoil, and the substratum. |
| SoilScientist | A soil scientist studies the upper few meters of the Earth’s crust in terms of its physical and chemical properties; distribution, genesis and morphology; and biological components. A soil scientist needs a strong background in the physical and biological sciences and mathematics. |
| SoilTexture | The relative proportion of sand, slit, and clay particles that make up a soil. Sand particles are the largest and clay parti-cles the smallest. Learn more about soil texture at www.soils4teachers. org/physical-properties. |
| SolubleBases | Elements (calcium, magnesium, sodium and potassium) that are present in soil as ions and form what is called Cation Exchange Capacity. The amount in the soil can be reduced through leaching |
| Subsoil | The soil horizon rich in minerals that eluviated, or leached down, from the horizons above it. Not present in all soils |
| Topsoil | The horizon that formed at the land surface. Mostly weathered minerals from parent material with a little organ-ic matter added. |
