AC-Ch. 3 Soil Science Flashcards
Actinomycetes
Group of soil bacteria resembling fungi. They play a role in the decomposition of organic matter and the release of mineral elements.
Aggregate
(1) Close cluster or mix of small particles of soil and/or organic matter of varying sizes that are bonded together. (2) Sand, gravel or small rocks in soil and/or used under paved surfaces. (3) Clusters of flowers or fruits that appear as a single unit. (4) Individual tree crowns that form a canopy.
Anion
Negatively charged ion.
Buffering capacity
Ability of a soil to maintain its pH.
Bulk density
Mass of soil per unit volume. Often used as a measure of compaction.
Capillary water
Water held in the capillary pores of the soil much of this water can move in any direction and is readily available to plant roots.
Cation
Positively charged ion.
Calcium. Magnesium. Potassium. Sodium. Aluminum.
What are the most abundant cations in soil?
CEC
Cation Exchange Capacity: The ability of a soil to attract, retain, and exchange positively charged cations. Affected by soil pH and particle size. A measure of soil fertility and clay composition.
Clay
Soil particles with a typical grain size less than .004 mm.
Field capacity
Maximum soil moisture content following the drainage of water due to the force of gravity.
Food Chain
A linear network of links in a food web, often starting with an autotroph, also called a producer, and typically ending at an apex predator, detritivore, or decomposer.
Gravitational water
Water that drains from the larger soil macropores due to the force of gravity.
Horizon
Layer of soil within the soil profile.
Humus
Dark colored, stable form of organic matter formed by the decomposition of plant and animal matter, and a rich source of nutrients improving soil health.
Hydroxide
Polyatomic anion of hydrogen and oxygen present in alkaline substances that attracts the monoatomic hydrogen cations in acids.
Ion
Atom or a group of atoms with a positive or negative charge.
Leach (leaching)
Tendency for elements or compounds to wash down through or into the soil.
Loam
Soil texture classification based on a certain ratio of sand, silt, and clay. Considered ideal for plant growth.
Macropore
Relatively large space between soil particles (mainly betweeen aggregates) that is usually air filled and allows for water movement and root penetration.
Micropore
Space between soil particles that is relatively small and likely to be water filled.
Mineralization
Process in which an organic substance is converted to or trapped in inorganic substance.
Nematode
Microscopic roundworm. Many are beneficial organisms, but some feed on plant tissues and may cause disease or damage.
Nutrient cycling
Movement of mineral elements within an ecosystem as organic matter decomposes, releasing bound nutrients back to plants.
Organic layer
Layer of organic at the soil surface.
Parent material
Soil bedrock or base material from which a soil profile develops.
Permanent wilting point
Point at which a plant cannot pull any more water from the soil and suffers permanent damage.
pH
Unit of measure that describes the alkalinity or acidity of a solution. Negative log of the hydrogen ion concentration.
Rhizosphere
Soil area immediately adjacent to and affected by plant roots. Typically has a high level of microbial activity.
Root exudates
Sugar and other substances that are released into the soil as the root caps and external layers are sloughed off.
Saline soil
Soil with a high concentration of soluble salts. Can cause poor plant growth.
Sand
Soil particles with a size between.06 and 2.0 mm in diameter.
Silt
Soil particles with a grain size between .004 and .062 mm.
Sodic soil
Soil with relatively low levels of soluble salts and a concentration of sodium high enough to adversely affect soil structure.
Sodic soil
Symptoms include waterlogging erosion soil surface crusting and poor plant growth.
Soil compaction
Compression of the soil often as a result of vehicle or heavy equipment traffic that breaks down soil aggregates and reduces soil volume and total pore space especially macropore space.
Soil food web
(1) Complex network of interconnected food chains within the soil ecosystem. (2) The diversity of organisms living, moving, and interactng in the soil.
Soil profile
Vertical section through the soil and all of the soil horizons.
Soil structure
(1) Arrangement of soil particles into aggregates. (2) The shape, size, strength, and arragement of the aggregates within the soil.
Soil texture
Relative fineness or coarseness of the inorganic, mineral, soil particles—specifically the relative proportions of sand, silt, and clay.
Structural cells
Modular system consisting of units of soil and integrated support structures that serves as both a foundation for paved surfaces and a hospitable environment for tree root growth.
Structural soil
Pavement substrate that can be compacted to meet engineering specifications yet remains penetrable by tree roots in the urban environment.
Structural soil
Composed of angular crushed stone clay loam and hydrogel mixed in a weight ratio of 100:20:0.03
Suspended sidewalk
Sidewalk that is reinforced and supported with piers or other structures so that it does not rely on compacted subgrade or soil for support.
