Soils Exam 1 Flashcards
Soil spatial variable
Large to micro scale concerning climatic vegetation to aggregates
Gelisols
Very cold climate
Permafrost
Slow soil formation
High organic content due to slow decomposition
Spodosols
Acid soils with thin subsurface
Form in coarse textured parent materials
Form under coniferous vegetation
Alfisols
Moderately leached forest souls
Temperate humid and subhumid regions
Very productive
Found in upper Midwest of USA
Weathering involves both
Destruction and synthesis
4 processes of soil formation
Transformation
Organic parent material
Forms where plant growth exceeds rate of decomposition
Aridisols
Light color low organic matter
High salts and minerals
Deserts
Glaciel till parent material
Material deposited directly by Glaciel ice
E horizon
Bleached almost white color, often sandy. Elucidation of clay. Fe, Al
6 functions of soil
Support plant growth Control fate of water Recycling system Modify atmosphere Habitat for organisms Engineering medium
C horizon
Un consolidated material
Mollisols
Dark, soft and if grasslands
Thick and dark
Crumb like structure
Important for agriculture
Alluvial parent material
Sediments deposited by streams and rivers and deposited into floodplains, deltas, etc
Biochemical reactions double fur every ___ degree Celsius increase in temperature
10
Degree of weathering is related to ________ rather than total precipitation?
Effective
Soil interface consists of:
45% solids
5% organic matter
O horizon
Organic materials above mineral soil
Andisols
Volcanic ash
Highly organic
High water and naturally fertile
Covers significant land in PAC NW
Eolian parent material
Silt sized material and smaller carried by wind. Volcanic ash
Lacustrine parent materials
Materials deposited when glacial out wash turns into lake. Stratified
A horizon
Topmost mineral horizon containing enough organic material to blacken. Coarse texture
Histosols
Mainly organic
20-30% organic matter
Mostly found in pears and mucks
Vertisols
Clay rich
Sink and swell
Bad for engineering, mixing, tilling.
Dark color doesn’t indicate high OM
Glacial out wash
Coarse sands and gravel deposited by glacial out wash
Oxisols
Highly weathered in humid tropical
Rain forests
Well structured
High clay content rich in Fe and Al oxide minerals
Colluvial parent material
Angular Rick fragments transported downhill by gravity
Marine parent material
Sediments carried by rivers or streams into marine environments
B horizon
Accumulating clays. Parent material no longer visible
5 master soil horizons:
O A E B C
Ultisols
Strongly leached acidic forests
Humid temperate and tropical regions
Intensive weathering
Many yellow red clays from Fe oxides
Entisols
Very recent Entering a horizon Great diversity Steep Ricky settings Fly vial and alluvial can be productive
Residual patent material
Develops from underlying Rick and is not transported
Inceptisols
More developed than entisols
Being invented into souks
Fertile inPac. NW infertile in pa
Soil color factors
Organic matter, water, presence and oxidation state of iron and manganese
Is silt cohesive?
No
Physical processes of soil aggregates
Wetting drying, freezing thawing
Field capacity:
Only water held against gravity renaming
-10 to -30 kPa
Per meant wilting point:
When plant roots can no longer extract water
Around - 1500 kPa
Soil texture
Different sized particles
Sand size?
2 - .05 mm
Silt size?
.05 - .002 mm
3 types of water movement in soil:
Saturated flow : gravity
Unsaturated flow: matric
Vapor flow
Clay size?
.002 >
Forces that affect potential energy of soil water:
Gravity
Matric
Osmotic
______ - many primary soil particles held in a single cluster
Aggregate
2 types of soil density?
Particle density - mass of solids/volume of solids
Bulk density - mass of solids/ volume of soil
Chart used for soil color
Munsell color chart
10YR 5/6
What does this describe?
Hue
Value
Chroma
Soil properties
Color, texture, structure, density, porosity, compaction
Soil texture influences:
Bulk density, water holding capacity, cation(gas) exchange, aeration, erodability, drivability, strength
Biological processes of soil aggregates
Burrowing organisms, plant root extension, root, fungal, and bacterial secretions
Percentage if earth’s freshwater in soils?
33%
Volumetric water content
Volume of water present per unit volume of dry soil
Gravimetric water content
Mass of water present per unit mass of dry soil
Tortuosity
Soil pores are not smooth like glass capillaries and move slower through tortuous paths
As water potential gradient increases, so dues_____
The rate if flow
