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LARE Section 4:
Soils
24
Architecture
Professional
11/07/2012

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Cards

Term
What are the 5 ideal natural soil horizons?
Definition
O Horizon: organic
A horizon: topsoil
B horizon: subsoil
C horizon: substratum or parent material
R horizon: bedrock
Term
Describe the O horizon.
Definition
(organic) a mulch layer that reduces evaporative water losses, maintains surface temps, contributes organic matter.
Term
Describe the A horizon
Definition
Topsoil: incorporated organic matter, organism population, rooting medium for most plants
Term
Describe the B horizon.
Definition
Subsoil: added rooting volume for stability, nutrients and water storage.
Term
Describe the C Horizon.
Definition
substratum: deep rooting and drainage volume. More important to good plant growth in shallow soils.
Term
Describe the R horizon.
Definition
Bedrock. consolidated soil material from which the soil profile may have been derived.
Term
What have insurers listed as the major cause for liability claims against landscape architects?
Definition
Soil failures
Term
What is the ideal depth to bedrock, or the impervious horizon?
Definition
At least 24-30 inches for most planting designs, 36" ideal for most situations.
Term
What are the guidelines for coarse fragments in topsoil?
Definition
stones and or building rubble should be less than 2" in diameter and less than 25% by volume within 24" of soil surface.
Term
What are effective amendments for heavy texture soils?
Definition
organic matter, expanded shale, calcined clay or other similar materials in appropriate proportions. contact soil scientist for best specs
Term
What is the most influential soil physical property?
Definition
Soil texture or particle size distribution
Term
List several designed soil properties.
Definition
soil texture
density
susceptibility to compaction
structure formation,
drainage and aeration
relative fertility
Term
How is soil texture defined (ratio)
Definition
proportion
sand:silt:clay
Term
What are the particle size ranges for sand, silt and clay?
Definition
Coarse Fragments: >2mm
Sand: 2-0.05mm
Silt: 0.05-0.002mm
Clay: <0.002
Term
What are typical organic matter dry weight specifications for topsoil/subsoil?
Definition
5-10% dry weight for topsoil
1-3% for subsoil
*Calculate volume values by multiplying dry weight by 2.2 (this is for landscape soils NOT potting soils which have more organic matter).
Term
What is the best ASTM soil test for general soil info?
Definition
*(best all around) Std. Mthd. for Saturated Hydraulic conductivity, Water Retention, Porosity, Particle Density and Bulk Density
Term
What is one method to lower soil pH in an appropriate manner?
Definition
application of elemental sulfur (NOT over-adding organic matter)
Term
What are the guidelines for placing soil on flat terrain?
Definition
Place in lifts no greater than 6", compacting each level to ensure elimination of air pockets and soft spots.
Term
What are the guidelines for placing soil on slopes?
Definition
The surface should be deeply scarified (6" or more using using a chisel plow), with removal of some of the the stone in the case of the stoney surface. On steeper slopes the existing sub grade should be stepped or terraced.
Term
What are the 3 layers of design soil profiles?
Definition
S-1: topsoil
S-2: subsoil
S-3: drainage layer
Term
Describe the garden profile for general purpose garden soil.
Definition
S1: 0-6" Loam to silt loam with 20% volume basis organic matter
S2: 6-8" Loam with 5% vol. organic matter
S3: 4"+depth of sandy loam
Term
What are the basic guidelines for tree planting without understory?
Definition
Excavate pit to depth slightly less than depth of rootball; flare out walls of pit; infill with UNAMENDED soil, loosening of soil is adequate; mulch layer 4" or less, extends from near root collar, which is NOT covered, out to beyond the disturbed soil.
Term
What is the max recommended slope acceptable for tree planting?
Definition
2:1, unless special geotechnical engineering subsurface provisions are made to stabilize the slope.
Term
What are some general guidelines for designing planting berms?
Definition
1. provide deliberate drainage
2. existing soil to be covered by the berm should be shaped with a slight mound longitudinal to the berm.
3. Only use geotextile if the berm is being built on poorly drained soil.
4. Keep slopes shallow (2:1 or 3:1) so they are accessible for maintenance.
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