Chapter 15 Outline Apes
Chapter 15 Outline * Soil is the relatively thin surface layer of Earth’s crust consisting of minerals and organic matter modified by natural actions like… * Weather * Wind * Water * Organisms * Soil is formed from parent material, rock that is slowly broken down or fragmented into smaller particles by… * Weathering Processes Biological * Chemical * Physical * Topography, a region’s surface features such as the presence or absence of mountains and valleys, is also involved in soil formation. Soil Composition: soil is composed of 4 distinct parts, minerals that make up 45% of a soil. * Organic Material (5%) * Water (25%) * Air (25%) * Mineral portion which comes from weathered rocks provides anchorage and pore space for air and water. * Age affects mineral composition * Australia, South America, India have old infertile soil * Litter (dead leaves and branches on the soils surface) * Humus: Black or dark brown organic material that remains after decomposition has occurred. Illiviation: The deposition of leached material in the lower layers of soil * Soil Horizons: * O-horizon (accumulation of plant litter) * A-horizon (accumulation of organic matter of humus) * E-horizon (heavily leached) * B-horizon (accumulation of clay and nutrient materials) * C-horizon (weathered pieces of rock) * Solid Parent Material (bedrock) * Soil Organisms: * Ecosystem Services: maintaining soil fertility * Castings: bits of soil that have passed through the gut of an earthworm re deposited at the soil’s surface. * Mycorrhizae: helps plants absorb adequate amounts of essential nutrient minerals. * Mycelium: fungal threadlike body * Soil Texture refers to the relative proportions of different sized inorganic mineral particles of sand, silt, and clay. * Sand-largest soil particle * Silt * Clay * Soil Acidity is measured using the pH scale 0=extremely acidic, 7=Neutral, 14=alkaline Soil Property| Sandy Soil| Loam| Clay Soil| Aeration| Excellent| Good| Poor| Drainage| Excellent| Good| Poor|
Nutrient holding Cap. | Low| Medium| High| H2o holding cap| Low| Medium| High| Workability (tillage)| Easy | Moderate| Difficult| * Major Soil Groups: * Spodsol: in cold climate. Characteristic of evergreen forests (Great Lakes) * Alfisol: in humid climate with hot summers and cold winters. Temperate deciduous forests (Michigan) * Millisol: in semiarid climate with hot summers and cold winters. Temperate grassland (North Dakota) * Ardisol: in dry climate. Characteristic of desert. Nevada) * Oxisol: in wet warm climate, characteristic of tropical rain (Hawaii) * Sustainable Soils Use: The wise use of soil resources, without reduction in soil fertility, so that the soil remains productive for future generations. * Natural Resources Conservation Service: measures the rate of soil erosion at thousands of sites across the Unites States. * AMERICAN DUST BOWL * Salinization: The gradual accumulation of salt in a soil, often as a result of improper irrigation methods * Desertification: Degradation of once- fertile rangeland, or tropical dry forest into nonproductive desert. 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. * Crop Rotation: The planting of a series of different crops in the same field over a period of years. * Contour Plowing: plowing that matches the natural contour of the land * Terracing: A soil conservation measure that involves building dikes on hilly terrain to produce level areas for agriculture. * Preserving Soil Fertility Commercial inorganic fertilizers: are manufactured from chemical compounds and their exact compositions are known *Because they are soluble they are immediately available to plants *Commercial inorganic fertilizers are available in the soil for only a short period because they leach away. * Agroforestry: Concurrent use of forestry and agriculture techniques on the same land area to improve degraded soil and offer economic benefits. * Conservation Reserve Program (CRP) : A voluntary subsidy program that pays farmers to stop producing crops highly erodible farmland.
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