ch 15 vocab

1. Soil: the uppermost layer of Earth’s crust, which supports terrestrial plants, animals, and microorganisms.
2. Weathering Processes: when soil is formed from parent material, rock that is slowly broken down, or fragmented into smaller and smaller particles by biological, chemical, and physical processes.
3. Topography: a region’s surface features, such as the presence or absence of mountains and valleys, is also involved in soil formation.
4. Humus: the black or dark brown organic material that remains after much decomposition has occurred; a combination of organic compounds binds to nutrient mineral ions and holds water.
5. Leaches: percolates; the process by which dissolved materials (nutrients or contaminants) are washed away or filtered down through the various layers of the soil.
6. Illuviation: the deposition of leached material in the lower layers of soil.
7. Soil Horizons: the horizontal layers into which many soils are organized, from the surface to the underlying parent material.
8. Soil Profile: a vertical section from surface to parent material, showing the soil horizons.
9. O - Horizon: uppermost layer of soil; rich in organic material; accumulates plant litter as it gradually decays (desert- completely absent)
10. A - Horizon: topsoil; dark and rich in accumulates organic matter and humus; granular texture and is somewhat nutrient-poor owing to the gradual loss of many nutrient minerals to deeper layers by leaching.
11. E – Horizon: in some soils; develops between the A and B horizons.
12. B - Horizon: light-colored subsoil beneath the A-horizon; is often a zone of illuviation in which nutrient minerals that leached out of the topsoil and letter accumulate.
13. C – Horizon: contains weathered pieces of rock and borders the unweathered solid parent material; below most roots and is often saturated with groundwater.
14. Ecosystem Services: Important environmental benefits, such as clear air to breathe, clean water to drink, and fertile soil in which to grow crops, that ecosystems provide.
15. Castings: bits of soil that have passed through the gut of an earthworm which are deposited on the soil surface.
16. Mycorrhizae: help plants absorb adequate amounts of essential nutrient minerals from the soil.
17. Mycelium: threadlike body of the fungal partner which extends into the soil well beyond the roots.
18. Nutrient Cycling: the pathway of various nutrient minerals or elements from the environment through organisms and back to t he environment.
19. Sustainable Soil Use: the wise use of soil resources, without a reduction in the amount or fertility of soil, so that it is productive for future generations.
20. Soil Erosion: the wearing away or removal of soil from the land.
21. Conservation Tillage: a method of cultivation in which residues from previous crops are left in the soil, partially covering it and helping to hold it in place until the newly planted seeds are established.
22. Crop Rotation: the planting of a series of different crops in the same field over a period of years.
23. Contour Plowing: plowing that matches the natural contour of the land.
24. Shelterbelt: a row of trees planted as a windbreak to reduce soil erosion of agricultural land.