Term
| Soils form through the interaction of all four of Earth’s ‘spheres’: |
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Definition
–Atmosphere supplies oxygen and carbon dioxide for plant photosynthesis and soil chemistry
–Hydrosphere provides soil moisture
–Lithosphere provides minerals that are vital components of soil
–Biosphere is the source of organic material in soil |
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Term
| Physical and chemical weathering involving |
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Definition
| all four ‘spheres’ create soil from bedrock |
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Term
| Soil-forming processes are |
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Definition
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Definition
| Soils are a combination of minerals, organic matter, water, and air: |
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Term
| Soils are a combination of minerals, organic matter, water, and air: |
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Definition
–Rock and mineral fragments are produced by weathering of rocks and support the growth of plants
–Humus (decayed animal and plant remains) is a small, but essential, component |
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Definition
| A soil profile extends from the surface to the deepest extent of plant roots, or to where regolith or bedrock is encountered |
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Definition
| Hexagonal column 1-10 m2 in surface area used as the basic sampling unit in soil surveys |
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Definition
| Constitutes an identifiable series of soils in an area and used in preparation of local soil maps |
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Term
| Soils consist of different horizons |
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Definition
| (layers) having distinctive properties |
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Definition
| Physical and chemical weathering begins to disintegrate bedrock |
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Term
| Small organisms and plants |
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Definition
| begin to occupy loose material; organic acids, burrowing, and plant roots facilitate disintegration |
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Term
| Larger plants with deeper roots follow |
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Definition
| soil horizons begin to form from the top down |
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Term
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Definition
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Term
| Downward percolating water removes soluble constituents |
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Definition
| fine clays and oxides of Al and Fe from this zone |
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Term
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Definition
| Al and Fe brought down from above accumulate |
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Term
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Definition
| that was weathered to produce soil above |
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Term
| Soil color is a function of composition and chemical makeup: |
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Definition
Red and yellow: high in Fe-oxide
–Black: Richly organic
–White to pale: Presence of Al-oxides and silicates |
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Term
| Soil texture defined by the size of particles |
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Definition
Particles range from finest clays up to gravels
–Loam is a balanced mixture of sand, silt and clay beneficial to plant growth |
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Term
| Soil structure refers to the arrangement of soil particles |
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Definition
–The term ‘ped’ describes an individual unit of soil particles
–Peds can be described as blocky, platy, rounded, etc.
–Further described as fine, medium or coarse |
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Term
| Consistency of soil particles |
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Definition
–Reflects resistance to breaking and manipulation under varying moisture conditions
–Descriptive terms include sticky, plastic, friable, and brittle |
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Term
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Definition
| is a measure of the percent pore spaces in a soil |
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Definition
is a measure of how readily water is transmitted through soil:
–A function of the size of pore spaces and whether or not they are interconnected |
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Term
| Soil Moisture And Chemistry |
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Definition
| Plants operate most efficiently when soil has the maximum water availability for plant use |
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Term
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Definition
–Soil gases mostly nitrogen, oxygen and carbon dioxide
–Soil water is the medium for chemical reactions
–Soil colloids are tiny particles of clay and organic material that retain ions:
Can exchange important cations with soil solution |
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Term
| Soil fertility is the ability of soil to sustain plants |
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Definition
| Fertile soil contains organic substances and clay minerals that absorb water and elements needed by plants |
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Term
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Definition
| Soil colloids are tiny particles of clay and organic material that carry a negative electrical charge: |
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Term
| Soil colloids are tiny particles of clay and organic material that carry a negative electrical charge: |
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Definition
Attract positive (mainly metallic) ions (cations) critical to plant growth
–Prevents cations from being leached away |
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Term
| Cation exchange capacity (CEC |
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Definition
is a measure of how well soil colloids can store and exchange cations:
–High CEC soil has good fertility |
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Term
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Definition
| Mineral Ions For Later Absorption By Root Hairs |
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Term
| Major contributor to soil acidity is |
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Definition
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Term
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Definition
| require treatment with lime |
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Term
| Factors Affecting Soil Formation |
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Definition
climate
Vegetation, animal, and bacterial activity
Topography |
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Term
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Definition
–Most influential control of soil formation
–Warm temperatures and abundant precipitation accelerate chemical weathering and soil formation
–Cold, dry climates less favorable for good soils |
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Term
| Vegetation, animal, and bacterial activity |
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Definition
| Influence the soil’s physical and chemical properties, particularly pH |
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Term
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Definition
Steep slopes often have poorly developed soils
–Optimum terrain is a flat-to-undulating upland surface |
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Definition
| of finely-ground sediment left by the glaciers |
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Term
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Definition
Human intervention is a major impact on soils
A few centimeter’s thickness of prime soil require 500 years to mature
Global soil depletion and loss at record levels:
–35% of farmlands are losing soil faster than can form |
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Term
| Contributions to soil erosion and depletion |
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Definition
Removal of soil-holding vegetation
–Land is plowed regardless of topography
–Flood control structures block sediments and nutrients from replenishing floodplain soils
–Exposed soils may be completely leached of needed cations |
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Term
Dealing With Soil Erosion
Short term solutions |
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Definition
Fertilizers
–Increasing irrigation
–Planting higher-yield strains |
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Term
| Dealing With Soil Erosion |
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Definition
Potential yield from prime agricultural land will drop by 20% over the next 20 years
Addressing soil erosion is a major challenge for the future: |
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Term
| Addressing soil erosion is a major challenge for the future |
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Definition
| Growing population will require a larger agricultural system at a time when the amount of fertile soil is declining |
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Term
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Definition
Variations in soil formation over time and distances has led to a great variety of recognized soil types
Groups have been established using common characteristics
In the United States, a system is used called the soil taxonomy |
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Term
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Definition
Emphasis is placed on physical and chemical properties
–Six hierarchical categories exist
–Descriptive names are derived from Latin and Greek
–12 basic soil orders are recognized |
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Term
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Definition
Generally found in tropics and subtropical regions
Form on old land surfaces or from strongly weathered parent material
Soil heavily leached with most soluble constituents removed:
–Rich in insoluble iron and aluminum oxides |
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Term
| Poor soil for agricultural activity: |
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Definition
Can only support crops for a few years
–Slash-and-burn cultivation processes destroying rain forests
–Forest relies on recycling of nutrients from dead vegetation on the forest floor |
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Term
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Definition
A leaching process in humid and warm climates
Heavy precipitation leaches soluble minerals and silica from the A horizon:
–High eluviation removes basic cations and colloidal material
–Oxisols low in cation-exchange capacity
Iron and aluminum accumulate in the B horizon:
–Soil typically reddish and yellowish due to high iron and aluminum content
Most soluble material lost to the underlying groundwater system |
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Term
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Definition
Soils that develop in dry places such as deserts
Insufficient water to remove soluble minerals
May have a hard accumulation of calcium carbonate, gypsum, or salt in subsoil
Low organic content
Agricultural use requires large investments in water, drainage and fertilizers |
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Term
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Definition
Dark, soft soils that have developed under grass vegetation:
–Humus-rich surface horizon is rich in calcium and magnesium
–Excellent soil fertility
Generally found in prairie areas
Also found in hardwood forests with significant earthworm activity
Climatic range is boreal or alpine to tropical:
–Dry seasons are normal |
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Term
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Definition
Accumulation of calcium and magnesium carbonates in the B and C horizons of Aridisols and Mollisols
Can lead to a hardened layer called caliche
Occurs in regions where moisture demand is equal to or lower than precipitation |
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Term
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Definition
Moderately weathered soils that form under boreal forests or broadleaf deciduous forests
Rich in iron and aluminum
Clay particles accumulate in the subsurface layer in response to leaching
Fertile, productive soils:
–Neither too wet nor too dry |
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Term
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Definition
Products of long periods of weathering:
–Abundant water contributes to extensive leaching
–Water percolating through soils concentrates clay particles in the lower horizons
Restricted to humid climates in temperate regions and tropics where growing season is long
Poor soil quality |
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Term
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Definition
Soils found only in humid regions on sandy material
Common in northern coniferous forests and cool, humid forests
Low base-cation content requires the addition of nitrogen, phosphate, and potash (potassium carbonate) for agricultural use
Profile:
–The O horizon mostly acidic forest litter
–The A horizon includes a layer that is sandy and light-colored, lacking humus and clay
–The B horizon consists of accumulated organic matter along with iron and aluminum oxides |
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Term
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Definition
A process of soil acidification associated with forest soils (Spodosols) in cool climates:
–Surface horizon consists of organic litter from base-poor, acid-rich evergreen trees
–Acidic solution percolates through underlying A horizon, removing clays, iron and aluminum
– Dissolved constituents accumulate in B horizon
Any leached bases are transported downward and lost to the groundwater system below |
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Term
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Definition
Young soils having limited development and exhibiting properties of the parent material
Productivity varies:
–Very high for those formed on recent river deposits
–Very low for those forming on shifting sand or rocky slopes |
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Term
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Definition
Occur in regions with permafrost
Low temperatures and frozen conditions for much of the year
Slow soil-forming processes:
–Cold temperatures inhibit chemical weathering
Cryoturbation involves frost churning and mixing of soil in the freeze-thaw cycle:
–Disrupts soil horizons
–Organic material drawn down to lower layers
–Rocky C-horizon material lifted to the surface
–Results in little profile development
Patterned-ground common
Supports tundra vegetation such as lichens, mosses, and other plants adapted to the harsh cold |
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Term
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Definition
Young soils in which the parent material is volcanic ash and cinders, deposited by recent volcanic activity
High cation-exchange capacity (CEC)
Moderate fertility:
–Supports sugar cane, pineapple and other cash crops in Hawaii |
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Term
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Definition
Soils containing large amounts of clay, which shrink upon drying and swell when wet:
Found in subhumid to arid climates:
–Adequate supplies of water must be available to saturate soil after periods of drought
Soil expansion and contraction exert stresses on human structures:
–Sound familiar? |
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Term
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Definition
Organic soils with little or no climatic implications
Found in any climate where organic debris can accumulate to form a bog soil
Dark, partially decomposed organic material commonly referred to as peat |
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Term
| Which of the following does NOT add fertility to a soil? |
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Definition
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Term
| Oxisols form by a process known as ___________ |
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Definition
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Term
| Which of the following would most likely be a result of calcification? |
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Definition
| A hardened layer in the B horizon called caliche |
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Term
| The terms blocky, platy, and granular describe the soil's __________ |
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Definition
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Term
| ___________ soils occur in regions of permafrost where cryoturbation is common and supports tundra-type of vegetation. |
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Definition
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Term
| Where would soil be best developed? |
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Definition
| Temperate climate and flat to gently-rolling topography |
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Term
| This type of soil consists largely of partially decomposed organic material associated with bogs and is commonly referred to as peat. |
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Definition
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Term
| Within which soil horizon does clay, iron and aluminum brought down from overlying horizons accumulate? |
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Definition
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Term
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Definition
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Term
| Which of the following is LEAST characteristic of Spodosols and the process of Podzolization? |
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Definition
| form from young volcanic ash and cinders |
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