Ch. 3 Soil Science

Question 1

Aggregate

Answer 1

(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.

Question 2

Air-Excavation Device

Answer 2

Device that directs a jet of highly compressed air to excavate soil. Used to avoid or minimize damage to tree roots or under-ground structures such as pipes and wires. May also reduce hazards associated with excavation near pipes or wires.

Question 3

Anion

Answer 3

Ion that carries a negative charge.

Question 4

Buffering Capacity

Answer 4

Ability of a soil to maintain (i.e. resist change in) its pH.

Question 5

Bulk Density

Answer 5

Mass of soil per unit volume; used as a measure of soil compaction. Often written as grams/cubic centimeter.

Question 6

Capillary Water

Answer 6

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.

Question 7

Cation

Answer 7

Positively charges ion. In soils, the most abundant cations are calcium (Ca), magnesium (Mg), potassium (K), sodium (Na), and aluminum (Al).

Question 8

Cation Exchange Capacity (CEC)

Answer 8

Ability of a soil to adsorb and hold cations. Affected by soil pH and particle size. A measure of soil fertility and clay composition.

Question 9

Clay

Answer 9

(1) Soil particles with a typical grain size less than 0.004mm. (2) A soil predominantly composed of such particles.

Question 10

Compost

Answer 10

Organic matter that has been intentionally subjected to decay processes and is more or less decomposed.

Question 11

Field Capacity

Answer 11

Maximum soil moisture content following the drainage of water due to the force of gravity.

Question 12

Gravitational Water

Answer 12

Water that drains from soil macropores due to the force of gravity.

Question 13

Ion

Answer 13

Atom or group of atoms with a positive or negative charge.

Question 14

Leach

Answer 14

Tendency for elements or compounds to wash down through and/or out of the soil.

Question 15

Loam

Answer 15

Soil texture classification based on a certain ratio of sand, silt, and clay. Considered ideal for plant growth.

Question 16

Macropore

Answer 16

Relatively large space between soil particles that is usually air filled and allows for water movement and root penetration.

Question 17

Micropore

Answer 17

Space between soil particles that is relatively small and likely to be water filled.

Question 18

Mineralization

Answer 18

Process in which an organic substance is converted to or trapped in an inorganic substance.

Question 19

Mycorrhizae

Answer 19

Symbiotic association between certain fungi and absorbing roots of plants

Question 20

Nutrient Cycling

Answer 20

Movement of mineral elements (sometimes called nutrients) within an ecosystem as organic matter decomposes, releasing bound nutrients back to plants.

Question 21

Organic Layer

Answer 21

Layer of organic matter at the soil surface

Question 22

Organic Matter

Answer 22

Material derived from plant material such as wood chips, bark chips, or pine needles.

Question 23

Parent Material

Answer 23

Soil bedrock or base material from which a soil profile develops

Question 24

Permanent Wilting Point

Answer 24

Point at which a plant cannot pull any more water from the soil and suffers permanent damage.

Question 25

pH

Answer 25

Unit of measure that describes the alkalinity or acidity of a solution. Negative log of the hydrogen ion concentration. Measured on a scale from 0 to 14. Greater than 7 is alkaline, less than 7 is acid, and 7 is neutral (pure water).

Question 26

Pore Space

Answer 26

Air or water-filled spaces between soil particles.

Question 27

Rhizosphere

Answer 27

Soil area immediately adjacent to, and affected by, plant roots. Typically has a high level of microbial activity.

Question 28

Root Exudates

Answer 28

Sugar and other substances that are released into the soil as the root caps and external layers are sloughed off.

Question 29

Saline Soil

Answer 29

Soil with a high concentration of soluble salts. Can cause poor plant growth.

Question 30

Sand

Answer 30

Soil particles with a size between 0.06mm and 2.0mm in diameter.

Question 31

Silt

Answer 31

Soil particles with a grain size between 0.004mm and 0.062mm (coarser than clay but finer than sand).

Question 32

Sodic Soils

Answer 32

Soil with relatively low levels of soluble salts and a concentration of sodium high enough to adversely affect soil structure (symptoms include waterlogging, erosion, soil surface crusting, and poor plant growth).

Question 33

Soil Biological Properties

Answer 33

Characteristics of soil determined by the living inhabitants of the soil, such as fungi, bacteria, nematodes, earthworms, insects, and other animals.

Question 34

Soil Chemical Properties

Answer 34

Soil characteristics determined by the molecular content that affects pH, cation exchange capacity, buffering capacity, and other factors.

Question 35

Soil Compaction

Answer 35

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.

Question 36

Soil Food Web

Answer 36

Complex network of interconnected food chains within the soil ecosystem.

Question 37

Soil Horizon

Answer 37

Layer or zone of the soil profile with physical, chemical, and biological characteristics that differ from adjacent layers.

Question 38

Soil Physical Properties

Answer 38

Characteristics of soil, such as texture, structure, and bulk density, that are determined by the size and arrangement of the soil's mineral particles and other content.

Question 39

Soil Profile

Answer 39

Vertical section through the soil and all of the soil horizons.

Question 40

Soil Structure

Answer 40

Arrangement of soil particles into aggregates.

Question 41

Structural Cells

Answer 41

Modular system consisting of integrated support structures filled with soil that serves as both a foundation for paved surfaces and a hospitable environment for tree root growth.

Question 42

Structural Soil

Answer 42

Pavement substrate that can be compacted to meet engineering specifications yet remain penetrable by tree roots in the urban environment. Cornell University developed and trademarked CU-Structural Soil, composed of angular crushed stone, clay loam, and hydrogel mixed in a weight ratio of 100:25:0.03.

Question 43

Suspended Pavement

Answer 43

Paving option that transfers the load to the subsoil rather than to the top of the soil surface.

Question 44

Symbiotic

Answer 44

Association of two different types of living organisms that is not detrimental to either organism and is beneficial to one, and usual both, of the organisms.

Question 45

Water-holding Capacity

Answer 45

Ability of a soil to hold moisture.

Question 46

Salinity

Answer 46

Amount or percentage of salt in the soil.