Abiotic Systems Flashcards
Soil Series
a group of soils originating from the same parent material and having similar soil horizons in the soil profile, with the primary difference between them being their soil texture. Each soil series is named for a nearby geographic feature (e.g. town name). Soil series are divided into “phases” based upon their difference in texture, and the name of a soil phase indicates a feature that affects management. An example of a soil series and phase name would be “Hagerstown silt loam, 3 to 8 percent slopes.”
Through the USDA, the NRCS (National Resources Conservation Service) provides soil maps to the public that can be used to determine the soil series found at a specific site. If more detailed information (including soil chemistry) is required, the landscape architect can commission a soil survey for a site.
Soil Horizon
a layer parallel to the soil surface whose physical, chemical and biological characteristics differ from the layers above and beneath. Horizons are defined by obvious physical features such as color and texture.
Soil Profile
a vertical section of the soil through all its horizons and extending into the parent material.
Sand
The largest particle size, with soil particles between 0.05 and 2.0 millimeters in diameter
Silt
Fine soil particles between 0.05 and 0.002 millimeter in diameter that can be picked up by air or water and deposited as sediment .
Clay
The smallest particle size, with soil particles smaller than 0.002 millimeters in diameter
Loam
40% sand, 40% silt and 20% clay
Porosity
the void size between particles within a soil and can be expressed as the percentage of void space in a soil.
Well graded soil
a soil with a wide range and even distribution of soil particle sizes, in which the small soil particles fill the voids created by the larger grains.
Gap graded soil
a soil that contains various particle sizes, but in which gradation between sizes is broken by the absence of some particle sizes
Uniformly graded soil
a soil that consists of a single range of particle size.
Permeability
is the rate at which water moves through soil
Infiltration Rate
rate at which water flows into soil through small pores.
Percolation
downward movement of water in a soil
Hydric Soils
characterized by being heavily saturated with water for prolonged periods of time, and this prolonged saturation renders the soils anaerobic and generally results in the soils being bluish in color.
Bearing Capacity
the measure of a soil to decrease in volume under the pressure of a given weight. As such, knowing a soil’s bearing capacity can help determine where a foundation or roads can be constructed, given that soils with poor bearing capacity can lead to structural failures and other safety issues
Angle of repose
the maximum slope at which a loose material can be piled while remaining stable.
Soil elasticity
ability of a soil to return to its original shape after being subjected to a load condition.
Soil Plasticity
ability of a soil to be deformed under pressure without breaking apart
Liquid Limit
minimum moisture content at which a soil will flow under its own weight.
best practices to reduce soil erosion
Preserve existing vegetation
Reduce the total area of land disturbance
Stabilize excavated areas with seeding, sodding, matting or mulching and divert runoff away from these areas
Minimizing disturbance to steep slopes
Schedule clearing and grading activities during the dry season and suspend them prior to and during precipitation events
Locate non-point pollution sources (e.g. construction access roads) in areas that do not drain directly into water bodies
Introduce erosion control fencing, blankets and stabilize drainage channels with erosion-resistant materials (e.g. riprap)
Gully Erosion
widening, deepening, and headcutting of small channels and waterways due to erosion
Rill Erosion
removal of soil by running water with formation of shallow channels that can be smoothed out completely by normal cultivation.
Sheet Erosion
removal of a fairly uniform layer of soil or materials from the land surface by the action of rainfall and runoff water.
NPK Value
the ratio of:
Nitrogen (N)
Phosphorous (P)
Potassium (K)
Nitrogen does
Nitrogen supports plants’ rapid growth and encourages the healthy development of foliage and fruit
Potassium does
helps strengthen plants’ abilities to resist disease and plays an important role in increasing crop yields
Phosphorus does
helps a plant convert other nutrients into usable building blocks with which to grow