organically enriched, majority of plant roots found here
where most water is stored, roots can't really grow here, it's hard to modify subsoil
disintegration caused by temperature, water, wind, ice, and organisms.
> 0.08 mm diameter, earthworms and small organisms can move through, water can move through
< 0.08 mm diameter, hold water so tightly plants can't access it
the hydrogen don't attach to the water evenly, they make a v-shape instead and this causes the positive charges to cling towards the side weighed down with the two hydrogens therefore causing this property of water
one of the hydrogens makes a low-energy bond to an oxygen particle from another molecule of water. this causes water to have a higher boiling point, specific heat, and viscosity
the attraction of water molecules for each other
the attraction of water molecules for solid surfaces, causes some water molecules to be held rigidly at the surface of soil solids
results from the greater attraction of water molecules for each other than for the air above, causes an inward force at the surface
force caused by adhesion, reduced the energy state of water near particle surfaces
force caused by cohesion, reduces energy state of water in the soil solution
force pulling the water downward
process by which water enters the soil pore spaces and becomes soil water, takes place at the soil surface
process by which water moves downwards into the soil profile, rate is related to the soil's hydraulic conductivity
when water addition stops the largest pores will drain downward rapidly, when this flow becomes negligible the soil is holding the maximal amount of water useful to plants
all soil pores are filled with water, matric potential is close to zero, the soil will remain here only so long as water continues to infiltrate
maximum retentive capacity
the rate of plant water removal fails to keep up with the plant needs so the plant wilts
soil moisture is lowered below the wilting point, the water molecules that remain are very tightly held, most are absorbed by colloidal soil surfaces the water is held so rigidly that most of it can only move in the vapor phase
an area of land drained by a single system of streams and bounded by ridges that separate it from adjacent watersheds
how water is returned to the atmosphere
after plant use it is vaporized from the stomata on the surfaces of the plant leaves
precipitation is intercepted by plant foliage and returned to the atmosphere by evaporation without ever touching soil
the physical condition of the soil in relation to plant grown
Name three primary properties used to delineate soil horizons
color, texture, structure
soil solids approximate this percentage of a loam at field capacity
ions freely available for absorption by plant roots are found in this fraction
soil solution fraction
essential to plant respiration at interface of pedosphere and atmosphere
degradation of OM from plant residues is considered this type of soil profile developmental process
limestone PM weathers into this bivalent cation which is an example of what kind of weathering
name the five soil forming factors
time, biota, parent material, topography, climate
soils with equal amounts of each texture would be in which textural class
most weathered soil order
example of a clay mineral with extensive isomorphous substitution
a 1:1 silicate clay mineral
pH dependent charge, edge charges
vertisols are dominated by what types of charges
oxisols are dominated by what type of charge
pH dependent charge
clay with largest surface area
smectite, 2:1 w/ interlayer
what makes the water stay up in the fine textured stuff
matric potential (surface)
how does water move?
wet to dry, high to low potential, and macropores to micropores
highest capillary rise ultimately?
smallest radius means
how do you interpret the trends in ksat data with soil depth
it decreases with depth because there is higher clay that slows water movement because it's mostly micropores that just hold the water
range in soil water potential that defines the water available to plant roots
wilting point and field capacity
soil structure most prevalent in a C horizon
soil structure most prevalent in a B horizon
soil structure most prevalent in a E horizon
this soil separate is .05 to .002 and not gritty
way to increase soil temperature
plastic and organic mulches
three factors responsible for soil aeration
soil macroporosity, soil water content, O2 consumption
when temperature rises, what happens to microbial activity?
doubles for ever 10 degree increase
next terminal electron acceptor when there is no longer any O2
Name the four soil forming processes
additions, losses, transformations, translocations
Movement of soil constituents (organic or mineral) within the profile and/or between horizons.
The chemical weathering of sand and formation of clay minerals, transformation of coarse OM into decay resistant organic compounds (humus)
Through the movement of wind or water, or uptake by plants, soil particles (sand, silt, clay, and OM) or chemical compounds can be eroded, leached, or harvested from the soil, altering the chemical and physical makeup of the soil.
Materials added to the soil, such as decomposing vegetation and organisms (organic matter--OM), or new mineral materials deposited by wind or water.
what is the charge of O?
what is the charge of H?