APES: Soil
Living Organisms
These include nitrogen-fixing bacteria, Rhizobium, fungi, insects, worms, snails etc. that help decompose litter and recycle nutrients.
Shelter belts or Windbreaks
These structures reduce wind erosion, protecting the soil.
Soil
This is a thin layer on top of earth's land surface. It is a natural resource and deeply affects every other part of the ecosystem. It holds nutrients and water for plants and animals.
Climate
This is measured by precipitation and temperature. It results in partial weathering of parent material, which forms the substrate for soil.
Terracing
Transforms slopes into a series of steps enabling hilly cultivation without loosing lots of soil.
O Horizon (Surface litter)
Upper most layer. Leaves, waste, live organisms and partially decomposed organic debris including decomposing organisms. The dark, crumbly material resulting from decomposition of organic material is called humus. Maybe very thick in deciduous forests and very thin in tundra or desert.
Clay
Very fine particles. Compacts easily. Forms large, dense clumps when wet. Low permeability to water; therefore, upper layers become water logged.
Biological Weathering
Weathering that takes place as a result of the activities of living organisms.
Deposition
When eroded materials are deposited in a new location.
Overgrazing
When too many livestock destroy too much plant cover (soil degradation).
Irrigation
artificial production of water beyond that which crops receive from rainfall. 70% fresh water people withdraw used for immigration.
Desertification
form of degradation where more than 10% of productivity as a result of soil erosion, soil compaction, etc.
Land Degradation
general deterioration of the land. Diminishes productivity and biodiversity.
contour farming
plowing furrows and sideways across hillsides to protect the soil.
Fertilizers
substances containing essential nutrients. Can be inorganic (mined/synthetically manufactured), organic (remains of wastes of organisms) or compost (mixed produced when decomposers break down organic matter).
Waterlogging
when the water table rises to a point in the soil that water drowns plants, depriving them of access to gasses and essentially suffocating them.
Soil Composition
25% Water, 45% Mineral, 25% Air, 5% Organic Matter.
Rill Erosion
A type of erosion where fat-flowing water cuts small channels in the soil.
Sheet Erosion
A type of erosion where soil moves off as a horizontal layer.
Crop Rotation
Alternating crop type to protect the soil.
Soil and Water Conservation Act (1977)
An act that sets up soil and water conservation programs to aid landowners and users; also sets up conditions to continue evaluating the condition of US soil, water, and related resources.
Conservation Tillage
An array of approaches that reduce the amount of tilling to protect the soil.
Gully Erosion
An extreme case of rill erosion where, over time, channels increase in size and depth.
Humus
An important component to soil fertility because it is rich in organic matter.
Physical weathering (mechanical weathering)
Any process that breaks rocks down into smaller pieces without changing the chemistry of the rock. The forces responsible for it include wind and water.
Gravel
Coarse particles. Consists of rock fragments.
Loam
Contains about equal mixtures of clay, sand, silt and humus. Rich in nutrients. Holds water but does not become waterlogged.
Soil degradation
Deterioration of soil quality and productivity.
1935 Soil Erosion Act
Established Soil Conservation Service. Mandates the protection of the nation's soil reserves. Deals with soil erosion problems, carries out soil surveys, and does research on soil salinity. Provides computer databases for research.
C Horizon(Weathered parent material)
Horizon made up of partially broken down organic minerals. Large pieces that have not undergone much weathering.
Retention
How much water the soil holds. Too high = very soggy soil. Too low = very dry soil.
Percolation
How quickly water is absorbed and passes through soil. The higher the permeability, the lower this is.
Land Abuse by People
Includes over cultivation of fields, grazing rangeland with more livestock than that land can support, and deforestation.
Soil Erosion
It is the movement of weathered rock or soil components from one place to another. Destroys the soil profile, decreases water-holding capacity of the soil, and increases soil compaction. Causes damage to agriculture, waterways (canals), and infrastructures (dams). It interferes with wetland ecosystems, reproductive cycles (as in salmon), oxygen capacity, and pH of the water.
Oa Horizon
Layer with highly decomposed organic material.
Oi Horizon
Layer with slightly decomposed organic litter.
R Horizon
Made up of bedrock
A Horizon (Topsoil)
Made up of weathered rock and some organic matter that has traveled down from the O layer. Some living organisms and inorganic materials. Typically very thick in grasslands and important for plant growth.
Permeability
Measure of the ease with which a fluid can move through a porous rock. Influenced by porosity and the capillary of water. Higher porosity makes this higher.
Soil Erosion Prevention
Methods include building terraces to create level ground and stop soil from washing away, planting crops and ground cover (grass) to absorb water, making ditches to conserve water, putting down mulch, and making trash lines (putting weeds behind contours so that soil builds up behind, making a small terrace).
Food Security Act (1985)
Nicknamed swamp buster, this act discouraged the conversion of wetlands to non-wetlands. 1990 federal legislation denied federal farm supplements to those who converted wetlands to agriculture, and provided a restoration of benefits to those who unknowingly converts lands to wetlands.
Chemical Weathering
Occurs as a result of chemical reactions between water and other atmospheric gases, and the bedrock in a region.
Intercropping
Planting different types of crops in alternating bands.
Infiltration
Process by which water on the ground enters the top layers of soil. Measure of the rate at which soil is able to absorb rainfall or irrigation. Measured in in or mm per hr. Rate decreases as the soil becomes saturated
Topography
Refers to the physical characteristics of the location where the soil is formed. Factors that affect this includes drainage, lope direction, elevation, and wind exposure.
Soil fertility
Refers to the soil's ability to provide essential nutrients like nitrogen (N), potassium (K), and phosphorus (P) to plants.
Sand
Sedimentary material coarser than silt. Water flows through too quickly for most crops. Good for crops and plants requiring low amounts of water.
Silt
Sedimentary material consisting of very fine particles between the size of sand and clay. Easily transported by water.
Dust Bowel
Series of "black blizzards" that resulted from over use of the land and forced thousands out of their land.
B Horizon (Subsoil, Zone of Illuviation)
Tends to be yellowish in color due to the accumulation of iron, aluminum, humid compounds, and clay leached down from the A and E horizons. It can be rich in nutrients in areas where rainwater leeched (washed) nutrients from the topsoil.
Salinization
The build up of salts in the soil layer.
Monoculture
The planting of one type of crop. Creates a lack of genetic diversity which can make crops more susceptible to pests and diseases. It also leaches the soil unless crop rotation is performed.
Porosity
The ratio between the particles of rock and the open space between them. (volume space/volume soil) Greater: water flows through easier. Smaller: water flows through slower. This is larger in smaller particles than it is in larger particles because the space to soil volume ratio is greater in smaller particles.
soil texture
The relative abundance of sand, silt and clay.
Parent Material (Rock)
The rock or minerals from which the soil derives. The nature of this can either be native to the area or transported to the area by wind, water, or glacier, has a direct effect on the ultimate soil profile.
