6 functions of soil
Support plant growth
Control fate of water
Nature's recycling system
6 ways soils support plants
protection from toxins
less than .002mm
what is weathering?
a biochemical and physical process that involves both destruction and synthesis
3 ways to physically weather soils
water, ice, and wind abrasion
biochemical processes of weathering
water and acis produced by microbes
4 processes of soil formation
chemical or ohysical alteration
movement of soil by water
material input from outside source such as eroded sediment
material lost from soil due t water
what are the 5 master soil horizion layers?
Mainly organic materials above mineral layers
topmost mineral layer with a bit of organic matter to make it dark. coarse texture
maximum leaching loss, eluviation of clay, often sandy and white
zone of illuviation and clays. no longer can see parent material
unconsolidated material under solum
what are the 5 factors that influence soil formation
when do biochemical reactions double
when they are raised 10 degrees CELS
Thick Dark High base saturation
Thick Dark mineral horizoon derived from volcanic ash
thick organic horizon forming inw et areas
high activity silicate clays
veyr highly weather with fe and al oxides
illuvial horizon with accumulation of organic matter and al oxide
bx horizon of hgihly compacted dense brittle material that resisits any kind of penetration
6 soil physical properties
where do you find granular aggregates
where do you find angular or blocky aggregates
where do you find prismatic aggregates
b and c horizons
where do you find massive or structureless aggregates
mass of solids/volume of solids
mass of solids/volume of soil
what soil density includes pore space, and which does not?
particle density does not
bulk density does
size of macropores
greater than .08mm
size of mesopores
size of micropores
less than .08mm
what percent of the worlds fresh water is in soil
attraction fpo water molecules to eachother
attraction of water molecules to other surfaces
what is surface tension a result of
qwater molecules having a greater attraction to each other than air
name 3 forces that affect potential energy of water
water molecules being attracted to solid surfaces
attraction between water molecules and solutes
maximum retentive capacity 0kpa
macropores filled with air -10 to -30 kpa
permenant wilting point
all pores filled with air
volumetric water content
volume of water per dry soil
gravimetric water content
mass of water per mass dry soil
what are the three types of water movement in soil
gravitational flow from high to low elevation
matric flow from high energy to low energy
soil pores are not straight like a cappillary
plant available water
volume of water present between field capacity and PWP
whta is the typical residence time of water in soil
wtaer lost through evaporation from soil or transpiration from leaves
when does infiltration excess occur
the rate of precipiation exceeds the rate of infiltration during hard rains
when does saturation xecess occur
amount of precipiation exceeds water holding copacity during long rains
acid mine drainage
oxidation of pyrite produces extreme acidity and soluble iron and sulfur
the best to the worst way for chemicals to travel through soil
concentration fo what decreases with soil depth?
what are the 2 methods of soil gas exchange
mass flow and diffusion
what makes diffusion happen
the loss of electrons in a substance therefore increasing valence charge
gain of electrons therefore a decrease in valence charge
what is redox potential?
a measure of how aerobic or anaerobic a system is by measuring the tendency of a substance to give up or take electrons
what can anaerobic respiration lead to?
methane ethlyne dentitrification
what is a vernalization process?
seeds requiring a cold treatment before germination
at what temperature do biological processes cease
5 degrees celsius
at what high temperature does microbial activity die?
50-60 degrees celsius
soil freezing and pushing objects in it upward
what does rain do to the soil in the spring?
warms cool soils
what does rain do to soils in the summer?
cools hot soils
the fraction of sunlight reflected by land surface
how the slope of land affects solar radiation
What makes a charge variable?
what makes permanent charge
positive and attracted to negatively charged sites
negative and attracted to positively charged sites
some cations bind more strongly than others
what is cec
the amount of cations a soil can contain per unit mass
what happens to cec as soil ph increases
the cec increases
what happens to anion exchnage as ph increases
anioon exchange decreases
anions are _________
cations are _________
negative and attracted to positives in low ph
positive and attractued to negatives in high ph
what is ph
the concentration of H+ in soil solution
what happens to H+ concentration as ph increases
the H+ concentration goes down
What is a ph buffer
Something that is resistant to change in ph
At what ph do metals become very readily available
What is calcitic limestone vs dolomitic limestone?
When little Mg is present in liming materials it is calcitic
When high levels of Mg are in liming material it is dolomitic
What neutralizes acidity in liming material?
The carbonates, not the Mg and Ca
What are 4 factors to take into consideration when liming a soil?
Change in ph required
Buffering capacity of the soil
The type of liming material to be used
The fineness of the liming material
What is CCE?
The neutralizing value of liming materials.
CALCIUM CARBONATE EQUIVALENCY
What is Alkalinity?
The concentration of OH+
inverse to acidity which is the concentration of H+
Where do most alkaline soils exist?
In soils where evapotranspiration exceeds precipitation.
What is often deficient in alkaline soils? Which nutrient?
Microsutrients and Phosphate
Where do saline soils reside?
In arears where water runs through the profile and takes up salt. This runoff eventually resides somewhere and concentrates the salts afetr evaporation
How is salinity in soil measured?
How do you correct a saline soil?
Flush it with irrigation water that can actually run off without concetrating
GYPSUM can be used as a chemical alternative to lower Na
What do protists and nematodes prey on?
The primary decomposers
What 4 factors in soil that affect microorganism growth?
Moisture and Temperature
Soil fertility an ph
What are the 3 things that make up Organic Matter and what does OM contain in general?
Animal remains and excretes
Living soil microbes
What compounds decompose fast in soil and have a quikc nutrient release?
Sugars and proteins of green cover crop and manure
what compounds have a very slow rate of decomposition?
Lignin humus that comes from wood and compost
Name 4 ways to increase input of OM
return crop residue
add cover crop
diversifiy crop rotations
add other sources of OM
Name 4 internal providers of nutrients
biological nitrogen fixation
internal recyling of nutrients such as manure
What are 2 external nutrient providers
organic and inorganic fertilizers
what nutrient is affected by freeze thaw
What are 3 essential plant ELEMENTS
Carbon obtained from CO2
Oxygen obtained from O2 and H2O
Hydrogen obtained from H2O
When does volitalization occur?
When levels of ammonium are high
When does denitrification occur?
By biological means (bacteria) under anaerobic conditions
Of the macronutrients, which has very low concentrations?
What greatly increases P uptake?
What is the primary root of P to water systems?
Runoff and erosion
what nutrient is most abundant in soils, but not readily availabale?
Where is K held in soils?
Feldspars and Micas
Eroded sediments are enriched with NPK and OM more so than they soil from which they were eroded
A material or chemical present in soil greater than normal concentration
A material in soil present at a high enough concentratiuon to cause harm
Name 8 common types of contaminants
Hazardous organic chemicals
5 peices of technical information when soil contaminants are studied
Normal Background levels
How long the contaminant will persist
Toxicity to what organisms?
conversion to gaseous forms
3 fates of organic chemicals
What are 3 ways a chemical can decompose and which is the most common
BIOLOGICAL MOST COMMON
in situ soil remidiation
treatment of soil without removal
ex situ remediation
physical removal of soil.
favored in site with high concentrations in small areas
2 methods of ex situ remediation
mixing soil with solidifying agent to produce concretet like product
heating soil to a high temp like 2000 degrees celcius to produce a melt that is glasslike material
4 methods of in situ remediation
can solidification and vitrification be done both in situ and ex situ
appliation of electrical field to mobilize contaminant toward cathode or anode
covering a site with a layer of low permeability material
dillution with an uncontaminated material to reduce concentration
vegetate a site in order to prevent contaminant from being transported via water or wind erosion
removal of contaminant by plant uptake
What do chelates do?
increase metal solubility for phytoextraction via hyperaccumulators
What does a triple superphosphate do to soil in AMENDING SOIL
Makes contaminants very NOT bioavailable
What is an in vitro bioavailablity test do?
Mimics the human GI track
What is a bioreactor ex situ method?
soil introduced usually as slurry to allow complete control of environmental factors
what is a land farming?
Spreading contaminated soil over large areas to dilute concentrations and allow indigenous soil microbes to degrade contaminants
what microorganism ahs the greatest biomass?
organic to inorganic
inorganic to organic
what is the smallest pool of p
what are the 2 primary ways to lose SOM
erosion and decomposition
what favors net mineralization
a low C:N ratio less than 20:1
microorganism with greatest number in soils
3 properties of plant residue that affect decomposition
reduction of nitrogen to its gaseous form
ammonia to ammonium
does a high C:P ratio cause greater than 300:1
what are stable organic materials highly resistant to change
the passive pool
what process adds most notrogen to soil
biological nitrogen fixation
name 2 ways to limit p from agriculture to waterways
limit p accumulation and erosion
what type of n is not susceptible to leaching, denitrification, and volitalization?
an alkaline soils much p is held in this pool?
What are the three steps of soil testing?
classification of mineral soils based on sand silt or clay
what are the two factors that drive weathering
water and soil microbes
the attraction of water to a hydrophillic surface
what are the three steps of water erosion
detachment, transport, deposition
water in this pool has a residence time of 1-2 months
arrangement of soil particles in large aggregates
name 5 factors that determine soil formation
parent material, climate, bioto, time, topography
difference between water added and lost
soil water storage
void spaces between large soil particles that allow infikltration and aeration
what is removal of material from a zone or horizion?
What is it called when you add material to a horizion/zone?
weight of water in a given soil weight
gravimetric sil water content
what force primarily acts onw ater in saturated soil
from what does orange and red oxisols come
what do you call soil material weathered in place
residual parent material
what force moves soil water in unsaturated soils?
soil compacytion causes this parameter to increase
chemicals dissolved in water move fast to groundwater
what is effective precipitation?
water that infiltrates
This is better in flat areas than sloped areas
What are the three pools of acidicty
What form of aluminum is most toxic to plants
organisms that obtain their carbon and energy from sources previously produced by other organisms
Organisms that get their carbon and energy from minerals
organisms that get their carbon from materials previously produced by other organisms and their energy from the sun
organisms that get their carbon from CO2 and their energy from the sun
What macronutrient does manure contain a TON of
What is the main force behind soil detachment?
Why are erosion rates in forest soils slow?
Good O horizon and ground cover