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75 Cards in this Set
- Front
- Back
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Saprolyte |
residual material (weathered bedrock, in situ) |
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Drift |
fluvial (sorted) + glacial till (unsorted) |
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colluvium |
stuff that's fallen downhill |
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Periglacial solifluction |
cold, freeze/thaw patterns |
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Alluvium |
moved by streams (sorted/homogeneous) |
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Lacustrine sediment |
deposited in lake |
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O horizon |
Litter |
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A horizon |
Topsoil |
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B horizon |
Zone of accumulation |
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C horizon |
Parent material |
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E horizon |
Zone of loss |
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H horizon |
peat |
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Sand |
(2–0.05 mm) |
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Silt |
(0.05–0.002 mm) |
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Clay |
(<0.002 mm) |
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Hue |
Color |
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Value |
Greyness |
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Chroma |
Brightness |
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Color description |
hue value/chroma Red 10R 4/8 |
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Reasons soil OM is important |
- Food for consumer organisms - Provides nutrients (N, P, S, K) when mineralized - Contributes to soil structure by aggregation - Contributes to ion exchange capacity - Holds water - Stores carbon - Reduces temperature variaion |
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Glomalin |
Soil protein, sticky, allows aggregation |
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Mull humus |
Under grassland OM encorporated |
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Mor humus |
Under coniferous forests OM segregated |
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Primary minerals |
quartz, feldspars |
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Secondary minerals |
clays, oxides, hydroxides, carbonates |
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Minerals in solution |
NO3–, Cl–, Na+, Mg2+, Ca2+,H+, SO42–, HCO3–, Fe2+/3+, Al(OH)n |
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Soil aggregate |
A collection of soilparticles stuck together to form adistinct structural unit. Also knownas a ped |
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Aggregation |
Flocculation + cementation |
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Flocculation |
when theprimary particles (i.e. clayparticles) remain close togetherdue to interactive forces andform microscopic clumps orfloccules |
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Cementation |
Stabilization of floccules by cementing agent |
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Bulk density |
weight of dry soil in given volume |
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Humus |
dark, organic materialthat forms in soil when plant andanimal matter decays |
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Soil structure |
The arrangement ofthe soil aggregates and of the porespace between them |
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Soil structural types |
Crumb, Granular, Subangular blocky, Angular blocky, Columnar, Prismatic, Platy |
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Importance of soil structure |
Controls: water and air flow Provides space for: -growing roots -seed germination -soil organisms affects: -Rain infiltration -Run-off and erosion -Nutrient and pollutant run-off |
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Formation factors of soil structure |
swelling/shrinking of clays wet/dry cycles freeze/thaw cycles plant roots soil biology soil management |
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Rhizosphere |
Immediate environment of the root |
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Apical meristem |
drives root growth |
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Vascular cylinder |
(Procambium) xylem, phloem |
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Gravitropism |
turning or growth movement of a plant rootin response to gravity |
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Root functions |
1. Water Uptake 2. Nutrient capture 3. Anchorage into soil 4. Holds soil together 5. Nodules can fix N |
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Rhizodeposition |
Small organic molecules, allelopathic phenolics, mucigel |
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Soil organism functions |
Form soil material & structure- stick particles together into aggregates- biomechanical action: mix, sort, aerate Live - assimilate and excrete nutrients Die - return OM and nutrients to soil |
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Burrowers |
Moles, mice, foxes, badgers |
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Earthworms |
1. Recycling organic material 2. Increase nutrient availability -- increase mineralization of N and other nutrients 3. Improve soil structure -- casts promote crumb structure (from adhesive polysaccharides produced in their guts), creates size sorting 4. Food for other soil dwellers |
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Mycorrhizas |
Fungus-root, assist plants in assimilating limited nutrients |
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Soil water role in soil-plant system |
• Solution of minerals • Root–soil-solution exchange of solutes • Medium of biochemical processes • Transport within plant and soil organisms • Controlling aeration and redox conditions • Turgidity • Transpiration as driver of plant-water flow • Aggregation by adhesion & ion-exchange • Lubrication |
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Types of runoff |
Saturation excess runoff - groundwater goes up to surface Infiltration excess runoff - watertable is deeper but water exceeds soil infiltration capacity |
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hydraulic conductivity |
Speed at which water passes through soil Higher in sandy soils, lower in clayey |
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Soil water potential |
Flows from high potential to low |
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matric force |
Adhesion to soil solids -- flow to small pore spaces |
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osmotic force |
Attraction of water to solutes -- flow from low concentration to high |
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Field capacity |
water content after 1-3 days drainage under gravity higher with finer texture and more organic matter Gives optimal aeration to plants |
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Soil moisture deficit |
Amount of rain needed to bring soil to field capacity + value -- water deficit - value -- water surplus |
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Soil fertility |
The ability of soil to supply plant nutrients Dependent upon • Water, air, & redox potential • pH & acidity • Cation exchange capacity • Nutrient levels & availability • Toxin levels & exposure • Soil thickness • Soil structure, porosity, & bulk density |
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Organizing soil processes |
1. Mineral transformation -- turns rock into parent material 2. Growth, death, and decay of organisms 3. Redistribution of movable substances -- clay, Fe, Mn, Al 4. Structure formation 5. Liquid/gas exchange 6. Cumulation/erosion |
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Histosol |
organic matter, blanket peat |
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Technosol |
high content of artifacts, or sealed by concrete |
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Cryosols |
permafrost soils |
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Leptosols |
Shallow surface horizon over rock found on mountains |
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Podzols |
mineral soils, iron has been mobilized |
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Stagnosols |
mineral soils saturated because of drainage is prevented by textural/structural difference Gleying (mottled) |
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Gleysols |
mineral soils saturated because drainage is prevented by high water table includes sub-aqueous |
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Chernozems |
organic-rich surface mineral horizon, world's best soils |
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Ferralsols |
tropical, weathered, oxidized iron, few minerals |
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Luvisols |
Mineral soil with a subsurface increase in claycontent attributable to translocation |
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Soil forming factors |
1. Parent material 2. Climate 3. Organisms 4. Topography 5. Time |
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Pools of soil acidity |
Active acidity- H+ in soil solution, Small Exchangeable acidity - Al3 and H on soil colloids- easily exchanged by other cations, Big Residual acidity- Al3 and H bound by organic matter and clays- not easily exchanged, Biggest |
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Cation exchange capacity |
total capacity of a soil to hold exchangeable cations higher in basic soils (higher pH) |
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14 essential plant nutrients |
N, P, K, Ca, Mg, S, B, Cl, Mn, Fe, Zn, Cu, Mo, Ni |
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Threats to soil function |
sealing (#1 threat) erosion OM decline compaction salinization landslides contamination biodiversity loss |
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hypomagnesaemia |
magnesium deficiency from too much potassium |
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Steps to soil fertility management |
1. Soil Test 2. Soil pH and liming 3. Index 4. Slurry 5. Balance |
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Threats to soil/water quality |
Agriculture Forestry Irrigation Soil/land drainage Deforestation, overgrazing Urban/road sealing Erosion |
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CO2 emissions |
1/3 from land management, 2/3 from fossil fuels |
