Modified: 9/29/98

Key Concepts: Basic Soils

Months
• September
• October
• November
• December

Themes
• Basic Soils
• Land Use
• Sustainability
• Pollution

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2 Sep. Organization & Orientation

4 Sep. Humus & Minerals: Carbon & Rock Cycles

1. Decay
• Biomass decays to humus.
• Rock minerals decay (weather) to clays and plant minerals.
2. Cycles
• Carbon cycle links humification (decay) to photosynthesis and the building of new biomass.
• Rock cycle links weathering to remelting and the building of new minerals.
3. Fertility
• Both humus and clay hold nutrients on their surface by ion exchange.
• Decay releases the plant nutrients stored in minerals and biomass.
4. The Meeting Place
• Soil is the interface where the biosphere meets the lithosphere, hydrosphere and the atmosphere.
• The processes in soils link cycles that past through and intersect lithosphere, hydrosphere, atmosphere and the biosphere.

9 Sep. Flora & Fauna: Plants & Microbes

5. Producers, Consumers & Decomposers
• Plants are autotrophs--they support terrestrial food chains by fixing carbon and energy in their tissues.
• Soil fauna (from protozoa to insects to vertebrates) are heterotrophs--they consume on a food web supported by plants.
• Most soil microbes are heterotrophs, heterotrophic microbes are the decomposers.
• A few soil microbes are not decomposers, such as nitrogen-fixing bacteria or mycorrhizae fungi that form cooperative alliances (symbiosis) with the roots of certain plant species.
6. Roots
• About one third of the soil's breath comes from root respiration.
• Roots alter the soil and support increased biological activity around their roots.
• Root systems respond to soil conditions--biological competition and physical conditions such as compaction, aeration and flooding.
7. Cooperation and Competition
• Some soil organisms compete with or prey upon one another.
• Some soil organisms cooperate with one another the their mutual benefit.
8. Biological Activity
• Physical conditions in soils influence biological activity--flooding, compaction, aeration, and temperature.
• Soil respiration quantifies biological activity of all soil organisms--plants and microbes.

11 Sep. Structure & Horizons: Aggregates, Pores, Horizons

9. Visual and Tactile Properties of Soil
• The signature of a soil is its profile--the type, thickness, depth and sequence of horizons.
• Horizons are differentiated largely by properties one can see and feel--color, structure and strength of soil aggregates, texture, even smell.
• Color reflects drainage conditions and aeration.
• Texture implicates water-holding capacity and the rate of water movement through the soil.
• Texture is the relative proportions of sand, silt and clay.
10. Organization and Structure
• Humus and clay binds soil minerals into crumbs, the shape and strength of these crumbs depends on whether the primary adhesive is humus or clay.
• Three layers or horizons occur in nearly all soils: the A horizon where humus accumulates and clays are removed, the B horizon where clays and dissolved minerals accumulate, and the C horizon where biological activity is negligible and rock weathering is the sole order of business.
11. Horizons and Profiles
• Soils in the landscape exhibit a sequence of horizons--profiles--that are more or less strongly expressed.
• Not all soil that supports life has a profile.
• Soil geography draws upon the responsiveness of soils to their setting and the record of that responsiveness expressed in their profiles.
• The fundamental processes expressed in the profile are: additions, losses, transformations and translocations.

14 Sep. Soil Formation

12. Soils Reflect the Recent Natural History of a Locale
• "...soils are as varied as the rocks, climate, topography, organisms and the length of time that create them...a soil evolves".
• Erosion and deposition vary across landscapes, determining the stability of the land surface and the intensity of soil formation.
• The history of a soil is written in its profile--the horizons with their distinct color, structure, texture and mineralogy.
• In the 10,000 years it took for the last glacier to retreat from southern Wisconsin, a succession of tundra soils (gellisols), forest soils (alfisols) and prairie soils (mollisols) have come and gone.
13. Acidity & Alkalinity
• Mineral weathering pumps clays and plant minerals (ash) into soils--plant minerals are alkaline.
• Biological activity pumps humus and acidity into soils.
• Plants produce acidity by root respiration and to maintain charge neutrality by excreting acid cations as roots absorb alkaline nutrient cations.
14. Moisture Regime & Soil Formation
• Humid climates support more biological activity--humid-region soils usually are more acid.
• Humid climates leach soils more intensely--humid-region soils usually contain less alkalinity (plant minerals).
• Humid climates support more biomass--humid-region soils usually contain more humus.
• Humid climates weather minerals more intensely--humid-region soils usually contain more clay and are deeper.
15. Temperature Regime & Soil Formation
• Cool climates support less intense biological activity--cool-region soils usually contain more humus.
• Cool climates weather minerals less intensely--cool-region soils usually contain less clay and are more shallow.
16. Landforms & Soil Formation
• Erosion and deposition are not uniform throughout a landscape--some sites are actively eroding, others receive deposits, while yet others are relatively stable surfaces.
• Landform controls drainage throughout a landscape--some sites are dry because runoff prevents water from entering the soil while others are moist because water drains into or is trapped by the site.

Key Concepts: Land Use

Months
• September
• October
• November
• December

Themes
• Basic Soils
• Land Use
• Sustainability
• Pollution

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16 Sep. Resourse Preservation: Soil Geography & Mapping, Ecology

17. Soil Geography
• The physical environment (climate, biota, geology, landform) determines the course of soil processes that leave their imprint on the soil profile.
• Soils in the landscape are distinguished, classified and mapped according to the distinguishing features of their profiles--the nature and characteristics of the horizon sequence.
• Humus accumulation and translocation define Mollisols, Spodosols, and Histosols.
• Mineral weathering and clay transport define Spodosols, Alfisols, Ultisols, and Oxisols
• Unique conditions define Vertisols (swelling clays), Andisols (volcanic deposits), Aridisols (arid climate), Gelisols (permafrost).
• Climatic regimes (moisture and temperature) distinguish suborders--aquic, udic, perudic, ustic, xeric, aridic/torric--pergelic (permafrost), cryic, frigid, mesic, thermic, hyperthermic.

18 Sep. Resourse Preservation: Soil Geography & Mapping, Ecology

21 Sep. Resouce Development: Biological Activity, Habitat

23 Sep. Resouce Development: Biological Activity, Habitat

18. Soil Quality & Soil Degradation
• Soil quality is synonymous with soil health--an indicator of the vitality of the soil ecosystem.
• Soil degradation occurs when the physical conditions (aeration, moisture-holding capacity, friability) and chemistry (nutrient availability, pH, toxicity) of the soil become less favorable for life.
19. Influence of the Physical Environment on Biological Activity
• Optimal biological activity occurs within a rather narrow range of physical conditions.
• Though some organisms are adapted to extreme conditions, optimal conditions for most plants, arthropods, and microbes are similar.
• The most important factors influencing biological activity are: pH, temperature, aeration, and moisture content.
20. Wetland Soils
• Wetlands have several important functions in the environment: groundwater recharge, sediment entrapment, retarding runoff flow into streams & rivers, absorption of nutrients in runoff, habitat for unique fauna & flora.
• Though wetlands occur in many landscapes, they are common in recently glaciated landscapes because surface drainage is usually poor.
• Wetland soils are identified by vegetation (hydrophilic plants adapted to waterlogged soils) and the presence of gleying (blue, green, purple or dark gray colors) or mottling (splotches of yellow or red) caused by anaerobic conditions caused by waterlogging.
• As with any soil in the landscape, wetland boundaries are not abrupt--making wetland delineation often difficult.
21. Acidification and Neutralization
• Oxidation of sulfide ores and sulfides in coal--this oxidation reaction is responsible for both the acid rain and acid mine drainage. Sulfides in coal and sulfide ores oxidize upon exposure to air, producing significant quantities of acidity. Know the sulfide acidification reaction.
• Neutralization of acidity--whether produced by plants, acid rain or acid mine drainage--typically employs calcium carbonate or lime. Know the carbonate neutralization reaction.

25 Sep. Resouce Development: Biological Activity, Habitat

28 Sep. Prime Agricultural Land & Urban Development

30 Sep. Prime Agricultural Land & Urban Development

22. Soil Mapping Units
• Local landscapes provide a pattern of soil types related to local topography and parent material.
• A soil association is an identifiable grouping of soils that occur together in a predictable pattern that relate to parent material and location in the landscape. The association is mapped, not the individual soils.
• The soil series is a named soil that is widely distributed over an area as large as several states with well defined soil profile characteristics and a specific type location where a representative of this series can be found and examined.
23. Land Capability and Suitability Classifications
• The characteristics of a soil and its location in the landscape determine its suitability for alternative uses.
• Important soil profile properties include: acidity, clay content in the B horizon, erodibility (soil aggregate stability), internal drainage (rate water percolates into and through the soil), humus content, depth to bedrock.
• Important landscape properties include: slope steepness, surface drainage (potential for waterlogging), depth to water table.
• Overcoming limitations may require provisions to prevent erosion, provide drainage to reduce the risk of waterlogging, or amendment of soil chemistry to neutralize acidity or increase fertility.

Months
• September
• October
• November
• December

Themes
• Basic Soils
• Land Use
• Sustainability
• Pollution

• Top of Page
• Bottom of Page
• 230 Home Page

2 Oct. Prime Agricultural Land & Urban Development

5 Oct. (Mon.) Hour Exam #1

Months
• September
• October
• November
• December

Themes
• Basic Soils
• Land Use
• Sustainability
• Pollution

• Top of Page
• 230 Home Page