Chapter 3 Soil Science

Front 1

Actinomycete

Back 1

Group of soil bacteria resembling fungi. Acitinomycetes play a role in the decomposition of organic matter and the release of mineral elements.

Front 2

aggregate

Back 2

(1) close cluster or mix of small particles of soil and/or organic matter of various sizes that are bonded together; and/or sand, gravel, or small rocks in soil; and/or sand, gravel, or small rocks used under paving surfaces.

* (2) &(3) not pertaining to soil science

Front 3

Anion

Back 3

Ion that contains a negative charge, Contrast with Cation

Front 4

Buffering Capacity

Back 4

Ability of a soil to maintain its pH

Front 5

Bulk Density

Back 5

Mass of soil per unit volume. Often used as a measure of compaction.

Front 6

Capillary Water

Back 6

Water held in the capillary pores of the soil; much of this water cab move in any direction and is readily available to plants roots.

Front 7

Cation

Back 7

Positively charged ion.In soils the most abundant cations are Calcium (Ca), magnesium (Mg), Potassium (K), Sodium (Na), and Aluminum (Al). contrast with anion

Front 8

Cation Exchange Capacity (CEC)

Back 8

Ability of a soil to absorb and hold cations. Affected by soil pH. Measures soil fertility, clay composition, and engineering characteristics.

Front 9

Clay

Back 9

(1) Soil particles with a typical grain sixe of less then 0.004 mm. (2) Soil predominately composed of such particles. Contrast with Sand and Silt.

Front 10

Exudates

Back 10

Substance or solution that oozes out of injured plant cells or is secreted through membrane pores.

Front 11

Field Capacity

Back 11

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

*Compare to available water, gravitational water, and permanent wilting point.

Front 12

Gravitational Water

Back 12

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

*Compare to available water, gravitational water, and permanent wilting point.

Front 13

Horizon

Back 13

Layer of soil within the soil profile.

Front 14

Humus

Back 14

dark colored, stable form of organic matter that remains after most of the plant or animal residues have decomposed.

Front 15

Ion

Back 15

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

Front 16

Leach(leaching)

Back 16

(1) tendency for elements or compounds to wash down through the soil. (2) tendency for elements or compounds to wash into the soil. For example, alkaline compounds may leach from concrete, or heavy metals may leach from aggravates, and both may do plant damage.

Front 17

Loam

Back 17

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

Front 18

Macropore

Back 18

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

*Contrast with Micropore

Front 19

Micropore

Back 19

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

*Contrast with Macropore

Front 20

Mineralization

Back 20

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

Front 21

Mycorrhizae

Back 21

Symbiotic association between some fungi and the roots of a plant.

Front 22

Nematode

Back 22

microscopic round worm.many are beneficial organisms, but some feed on plant tissues and may cause disease or damage.

Front 23

Nutrient Cycling

Back 23

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

Front 24

Organic Layer

Back 24

Layer of organic matter at the soil surface

Front 25

Parent Material

Back 25

soil bedrock or base material from which a soil profile develops.

Front 26

Permanent wilting point

Back 26

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

Front 27

pH

Back 27

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

Front 28

rizosphere

Back 28

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

Front 29

saline soil

Back 29

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

Front 30

sand

Back 30

soil particles with a size between 0.06 and 2mm in diameter.

*Contrast with clay and silt

Front 31

silt

Back 31

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

*contrast with clay and sand

Front 32

sodic soil

Back 32

soils with relatively low levels of soluble salts and a concentration of sodium high enough to adversely affect soil structure (symptoms include water logging, erosion, soil surface crusting, and poor plant growth) Soils >12 SAR (sodium absorption ratio)

Front 33

soil compaction

Back 33

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 macro pore space.

Front 34

soil food web

Back 34

complex network of interconnected food chains in an ecosystem; in this case, in the soil.

Front 35

soil profile

Back 35

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

Front 36

soil structure

Back 36

arrangement of soil particles into aggregates

Front 37

soil texture

Back 37

relative fineness or coarseness of a soil due to particle size (sand, silt, and clay)

Front 38

structural cells

Back 38

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

Front 39

structural soil

Back 39

Pavement substrate that can be compacted to meet engineering specifications yet remains penetrateable by tree roots in the urban environment. composed of angular crushed stone, clay loam, and hydrogel mixed in a weight ratio of 100:20:0.03. Developed at the Urban Horticulture Institute, Cornell University, Ithica, NY

Front 40

suspended sidewalk

Back 40

Sidewalk that is reinforced and supported with piers or other structures so that it does not rely on compacted sub grade or soil for support.

Front 41

symbiotic

Back 41

association of two different types of living organisms that is often , but not always beneficial to each.

Front 42

water-holding capacity

Back 42

ability of a soil to hold moisture