Midterm 2 Flashcards
(112 cards)
1
Q
CEC
A
cation exchange capacity
number of exchangable cations which soil solids can adsorb (cmol/kg soil)
2
Q
Exchangable cations
A
cations which are readily displaced, by mass ion effect, from begat colloids which adsorbed on
3
Q
Kaolinite vs Montmorillonite CEC approx vales
A
k: 1-1, no shrink-swell, low SSA (3-15)
M: 2-1, shrink-swell, high SSA (~100)
4
Q
approz FE, Al osides CEC
A
~3 (weathered tropical environ)
5
Q
Examples of base cations
A
Ca2+, Mg2+, K+, Na+
6
Q
Base saturation
A
Fraction of cations on the ction exchange sites occupied by base cations
7
Q
Anion exchange capacity
AEC
A
Number of exchangale anions which soils can adsorb
8
Q
AEC with high pH
A
negative charge created!
9
Q
where salts accumulate
A
at top of soil wheninternal drainage is inadequite to drain
10
Q
Electrical Conductivity
A
EC
capacity of substance to conduct electric current
11
Q
Exchangable Sodium Percentage
A
ESP
identifies degree to which exchange complex is saturated with sodim
12
Q
ESP formula
A
(Exchangable sodium/CEC) times 100
13
Q
pH related to ESP
A
ESP <15=<8
>15=-7.5-8.5
>15=>8
LOL FIX
14
Q
consequenses of salinity
A
hurt plant growth
reduce water quality
soil erosion
damage infastructure
15
Q
SOM
A
soil organic matter
complex. resistant mixture of brown amorphous/ colloidal organic compounds from microbial decomp and synthesis
16
Q
OM input
A
forest litter, roots, animal excretion, microbial biomass
17
Q
physical props SOM
A
part dens= 900-1300kg/m^3 bul dens=180-200 f=~0.9m^3/m^3 therm props= all lower than mineral water retention higher than mineral
18
Q
primary components of SOM
A
non-humic substances
from plant/animal residues
partially decomped
20-30%
19
Q
Secondary components of SOM
A
humic subs from breaking down organic structures and synth new ones fulvic acids, humin, humic acids 60-80% Rather decomp resist
20
Q
Fulvic Acids
A
Smallest and “simple”
Soluble in any pH
brown colour in H2O
21
Q
Humic Acids
A
btw the two
many carboxyl groups to get acidic
reactive
22
Q
Humin
A
High molecular weight
“complex”
slow break down (decades of 100s)
23
Q
CEC and pH relation
A
CEC high at high pH and low at low pH
24
Q
low pH with humic groups
A
carboxyl groups undissociated (total negative charge=low)
can approach each other and bond
flocculate at low pH
25
properties determine humic
particle size
| number of carboxyle groups
26
Humic vs fluvic
H larger molecular weight
H have lower # carboxyle groups/ unit mass
H less active
27
Chem props of SOM
```
CEC:70-200 @ph=7
C conc is 58%
nut conc varies
nut ratios are less vary
C/N ratio indicates N availability
```
28
Chelate
organo-mineral complexes in which a metallic ion bonded to organic molecule (2+)
ring structure
29
organic molecules that chelate metals
substances that are synthesized by roots
humic subs that have multi carboxyle groups
synthetic subs
30
Dispersed chelates
contribute to nut availability
31
Flocculated chelates
contribute to nut deficiency
32
HUmic flocculate?
yes and tie up the nuts/metals
33
mineralization
overall process of conversion of an organic form of an element ro an inorganic state as result o fmicrobial decomp
34
Immobilization
conversion of element from inorganic to organcic in microbial tissues
renders element unavaliable
35
what does time needed fo rorganic matter decomp depend on?
```
soil conds (areation, pH, water cont, temp)
quality of added residues as food source for soil orgs (C/N ratio)
```
36
C/N ratio indicates what?
rate of residue's dcay and rate at which N is made available to plants
37
What does high C.N mean?
| narrow?
50:1 -Immobolization
not enough N
25:1 -net minerilization
38
SOM effects on OM
```
dark colour
increase aggregation/water/CEC retent
reduce plasticity/sticki
improve aretion/drain/buffer cap
provides nuts (NSP)
```
39
Biological effects of SOM
food for heterotrophics
| quality of SOM= decomp rate and organic mater accum
40
Organic soils
inclde soils developed largely from organic deposits
| Cdn sys of soil class >17%C by weight and organic horz must be >=40cm
41
what organ soils can be identified as?
peats, muck, soils of bogs, marshes, swamps
42
peat
very undecomp plant residue
recognizable
low Pb, High f
43
muck
sufficiently decomp
hard to identify OG plnt mats
dark and release nuts
high Pb, low f
44
drainage conds
affect props of organ horz found near soil surface
45
organic horizons on poorly drained sites
Of (fibric)- high in relativley undecmp, firbous mat
Om (mesic) high inless frbrous mat (inter decom)
Oh (humic)- dominated by well decomp org residue
46
Organic horizons on well drained sites
L- accum of relativley fresh undecomp residue
F-accum of partially decomp residue
H-accum of decomp organ matter, organic structs are indiscernible
47
L, F, H Horizons
forest floor
| most dynamic phase of forest environ
48
Ah
accum of organic matter in mineral horz
49
h
indicates accum of humus
50
Ae
been subject to leaching
51
e
indicates eluviation
52
humus forms
Mull
Moder
Mor
53
humus forms classifications based on ?
sequence, props and inferred origon of organic horizons
54
Mor
mated F horz
| abrupt boundary btw mineral and organic layer
55
Moder
loosely structure F horz
| gradual boundary btw org and min
56
Mull
F and H horizon thin or absence
organic-rich mineral soild horizon
Ah present
57
what does mor humus indicate
low site productivity
58
what does mull humus indicate
high site productivity
59
Soil organism
creatures that spend all or part of life in soil
60
how to classify soil organisms
size (macro>2mm width, Meso-0.2-2mm, micro
61
examples of micre, mesa and macro organs
micro=cant see with naked eye
meso= sometimes see (mtes)
Macro= earthworms, spider
62
ecological functions
herbivores= eat plants
detrivores= eat dead plant debris
fungivores (eat fungi)
bacterivoes (eat bact)
63
Predators and and Parasites
```
different class sys
consume animals and live off other organisms
```
64
two categories for getting C for soil orgs
heterotrophs (use organ compounds)
| Autotrophs (use CO2 as source)
65
two places for energy sources for soil orgs
Phototrophs (sunlight)
| Chemotrophs (chemical oxidation of certain compounds)
66
sections of phylogenetic tree of life
Prokaryotes = bact and archaea
| Eukaryotes
67
prokaryotes vs. eukaryotes
no nucleus membrane vs having one
68
archaea
survive harsh environs, ancient, before bact?
69
Flora vs fauna
flora=plants, nonanimla microbes (bact)
| Fauna= animals
70
PLants provide...
```
Prod OM
Root secretion (microbs depend on this) -associative microbe
```
71
Rhizosphere
root surface
lots microbes bc protiens and sugars there
zone of soil influenced by roots + microorgs
1-2 mm out of root
dynamic zone
72
what do Algae do?
chlorphyll (live near surface)= prod OM
| excrete polysaccharides= helps appregatione
73
Three types of algae
Green, diatoms, yellow-green
74
where algae grow best?
moist areas
| near surface for photosynthesis
75
Fungie
heterotrophic (mainly) aerobic orgs
76
what fungi responsible for
decomp of OM (convert dead OM to fungal biomass and immobilize nuts, accum humic rich OM)
colonize roots
killing plants (patho)
Biocontrol (disease)
77
Three types fungi
Yeast, Molds, Mushroom Fungi
78
Mycorrhizea
symbiotic plant fungi relationship
79
Hyphea
long thread like filaments in fungi
80
Mycellium
network of hyphae
81
Bacteria
most diverse/abundant group
82
what bact responisble for
form symbiotic assoc with roots of legumes and trees (n fixing)
Decomp OM thru nitrification
convert Nirtrate to Nitrogen or Nitrous Oxide (dentrifying)
83
Actinobacteria
```
filamentous bacteria
decomp soil org compoinds (cellulose and chitin)
hard to decomp
prod antibiotics
fix atm nitrogen N2-NH3
```
84
Cyanobacteria
chlorophyll, fix atm N, symbionts with lichens, protozoa, diatoms, algae
85
Endophytic Bacteria
fix atm N
| modulate lant hormones to increase plant grwth yield and protect agnst abiotic stresseprotect agnst pathos
86
classifications of fauna
macro
meso
micro
87
Vertabrates
| ex and role
Mice, moles, squirrels
| mix soil bc burrowing= better aeration, higher H2O filtration
88
Annelids ]define and ex
segmented worms
| most imp= earth worms
89
role of annelids
mix soil=up aer, roots, H2O filt
shred OM and mix with min soil= up decomp process and down Ah
Make casts=up aggregation and rich in nuts
90
Anthropods
| role and ex
SPIDER (jointed legs in pairs)
mix, shred and mix, up decom of OM,
predators=reglate pop
91
tardigrades
come back from anything
food source
grazers on bact, fungi, algae (nuts cycle)
pioneer species
92
Protozoa
| define
one cell
| primitive animal
93
role of protozoa
feed on fungi & bact or OM fragments (release NH4+ near roots)
supress disease by compete or eat pathos
food source
94
Nematodes
threadworms
bact-feeders, then excrete excess N as inorg N which increase mineraliz and nut cycle
predators
disease supress or devel
95
Nemotod diversity
hydrothermal
bacterial feeding
desmocolox
96
reasons for greater bio diversity in soil than air?
soil better habitat conditions (temp ect)
| more variety of food types
97
N sources in soil
```
bio fixation of N2
decomp of N compounds from atm by precip
fertilizer
plant residue
manure
```
98
losses of N in soil
```
plant removal
leaching
gaseaus (denitrification and NH3 volitilization)
Erosion (wind/H2O)
Ammonium fixation (clay complexes)
```
99
What is more common, leavhing or erosion in N losses
Leaching a lot more impactful
100
Bio fixation of N
NtriplebondN (inert)
conversion of N2 to NH3 by bact, cyanobact, and actinomycetes
release enzyme, break bond, get NH3
101
Mineralization
organic to inorganic
| complex to simple amino groups
102
immobilization
inorganic to organic
103
three forms of mineralization
| and what does each
aminization=heterotrophs (bact/fungi)
ammonification=heterotrops (fungi/actinomicetes)
Nitrification=chemo-autotrophic bact (bact/achaea)
104
Aminization
NH2 hydrolysis to NH3 then to NH4
| then uptake by plants and microrgs, nitrification and fixed by phyllo clays
105
Denitrification
biological reduction of NO3- to gaseous compounds
| NO3-NO2-NO-N2O
106
What happens to NO3-?
plant uptake, leahced, immobolized, denitrification
| microbially mediated or volatilization
107
what conds fo rdenitrification
anaerobic conds
| saturated, compacted soils
108
C/N ratio of 25:1
food source for microbs
| net mineralization
109
C/N ratio > 50:1
net immobilization
110
Saline Soil
```
low ESP (Na not main)
High EC=high Conc soluble salts
```
111
if soil has high salt conc
negative charge so attract water and not plant avail (osmotic)
112
what pH range for carboxyle groups dissociate and therefor eflocc or not
3.5-9.5 diss and flocc
| 4-6 is 85-90% diss
