Test 2 Flashcards
1
Q
Percent of water that’s ocean water.
Ice?
all other water?
ground water?
A
97.25%
2%
<0.05%
0.7%
2
Q
percent lake water?
Soil moisture?
Atmosphere?
Rivers
A
60%
33%
6%
1%
3
Q
What are two restrictions of water movement?
A
Rate of water supply from soil to root.
Rate of loss from leaves through evaporation.
4
Q
Evapotranspiration is affected by?(5)
A
Radiant energy- 540 calories to evaporate 1g water. Atmospheric vapor pressure Temperature wind soil moisture supply
5
Q
Different crops lose moisture at different rates(T/F)
A
True
6
Q
Transpiration ratio-
A
kg of water needed to produce 1kg of dry weight.
7
Q
Water vapor losses from soil surface and plants are determined by(4)
A
Climate
Plant cover
Water use efficiency
Length and season of plant growing period
8
Q
Ways to control soil evaporation?
A
Encourage soil cover
Mulches
Paper plastic mulches- high cost/high value crops
crop residue and conservation tillage- requires herbicide use.
9
Q
Percolation-
A
subsurface drainage, downward movement of water through soil.
-loss of soluable salts
10
Q
runoff-
A
surface drainage
11
Q
Leaching losses
A
loss of fertilizer
soil and water pollution
problems abated through split applications of fertilizers.
12
Q
infiltration-
A
absorption of water by soil
13
Q
If rate of rainfall exceeds rate of infiltration what happens?
A
soil ponding or surface runoff occurs.
14
Q
Land drainage occurs in what two regions?
A
Delta and flat coastal plains.
15
Q
Ex. of subsurface drains?(3)
A
Mole drain-lasts one season
Perforated plastic pipe- 90% of todays systems
Clay tile drains- to expensive for ag. popular 20-30 years.
16
Q
Benefits of drainage?(5)
A
reduces frost brewing helps soils warm up faster in spring Aeration easier to work fields Maintains productivity of irrigated soils.(no salting out)
17
Q
Perc test is used for what? how do you do one?
A
to determine percolation test. and determine solubility for a septic tank drainfield.
measure water in a hole over time.
18
Q
Aeration-
A
process of maintaining a supply of O2 to the soil
19
Q
Oxygen is important why?
A
respiration
organic matter decay
release organic nutrients(N,F,S)
reducing toxicities of elements( Mn and S)
20
Q
Diffusion-
A
random motion of molecules from an area of high concentration to an area of low concentration.
21
Q
Partial pressure-
A
the pressure a gas would exert if it alone were present in volume occupied by a mix.
22
Q
Factors affecting diffusion-
A
Texture-
Structure-
Water Content-
23
Q
Texture-
A
finer textures soils have more micropores
24
Q
Structure-
A
introduces large pores into fine textured materials.
25
Water Content-
drainage of macropores, oxygen diffuses more slowly through water than air.
26
Consequences of poor aeration(5)
```
reduces microbial activity
Accumulation of organic acids
Plant growth curtailed
Absorption of nutrients and water is decreased
Toxic compounds
```
27
Poor aeration-
if air filled porosity <20% plants will suffer from deterioration of roots.
28
Wetlands-
Soils that are water-saturated near the surface for long periods of time. Plants and microbes can grow and remove oxygen.
29
The weter end of a wet land is where?
where water is to deep for rooted emergent vegetation.
30
Wetland Delineation-
the drier end of wetland.
31
3 characteristics of a wetland-
Wetland hydrology, Hydric soils, Hydrophytic plants
32
Hydric soils-
soils subjected to periods of saturation
33
Soil temperature influences:
Microorganisms- o matter, decomposition
Plants- germination, nutrient uptake,transpiration/respiration.
Mineral weathering
34
```
Reflectance by clouds-
absorbence by dust and water-
Evaporation-
Radiation-
Reflection-
```
```
30%
20%
30%
5%
5%
```
35
what 10% of sun is absorbed by the soil?
10%
36
factors that affect energy entering the soil?
soil color
slope- closer to perpendicular the greater the absorption
Vegetation
37
Daily temperature fluctuations are greatest at the soil surface and decrease with debth.(T/F)
true.
38
How can you modify soil temp?
Moisture/Drainage
| Mulches(color)
39
What is the smallest soil particle?
Clay 1um, highly reactive w/ large surface area per unit mass.
40
CEC-
ions are absorbed on the colloid surfaces.
41
Mineral properties-(2)
Composition-kinds of atoms
| Crystallinity- arrangement
42
clays are composed of two basic crystal units:
Tetrahedrons
| Octahedrons
43
Interlocking units of Aluminum Octrahedron form what?
an octrahedral sheet.
44
what is an isomorphic substitution?
substitution of an ion of similar size for Si or Al that occur during crystal formations. has charge imbalance but isnt negative.
45
1:1 Clay minerals are made of?
1 tetrahedral sheet and 1octohedral sheet, share oxygen atoms. H-bonds
46
2:1 Clay minerals are made of?
1 octohedral and 2 tetrahedral sheets, share oxygen linked sheets.
47
Kandites
1:1 Clay mineral
CEC 2-10 cmolc low reactivity
broken edges, non explanding.
48
Smectite-
2:1
CEC 80-120 cmolc
highly reactive, explanding, high surface area
49
illite-
2:1
| CEC is 20-40 medium
50
vermiculite-
similar to illite
| CEC 120-150,limited expanding,high surface area.
51
Chlorite-
2:1:1
| CEC 20-40, medium ,increased strength of bonding.
52
other sources of charges in soil:(3)
Exposed crystal edges
Fe and Al oxides
Humus
53
Cations-
positively charged ions
54
Clays-
negativly charge
55
Cation adsorption-
electrostatic attraction, not readily leached
56
Cation exchange-
replacement of one cation for another on the exchange site.
57
CEC definition-
ability of soil to hold and exchange cations, measure of the basic fertility status of the soil
58
Mole-
6.02x10^23 ions, mass of 1 mole of an ion
59
equivalent-
quantity of an ion that will supply the same total charge as 1 mole of H+
60
Predominant cations
```
Ca+2
Mg+2
H+
Na+
K+
Al+3
```
61
factors influencing exchange reactions-(4)
Concentration of ions
Number of charges on ions
Hydrated radius of ions
pH
62
pH-
master variable that affects many soil chemical and biological properties.
63
Why is pH important?
Availability of nutrients
plant species that will grow
Activity of soil microorganisms
Mobility and breakdown of pollutants
64
An Acid donates what? and A base excepts what?
protons(H+) and a Base accepts the proton(H+)
65
What is the end result of an acid and base combining?
formation of water and a salt.
66
pH is the unit of measure for what?
acidity and alkalinity
67
Buffer-
a substance that has the ability to resist changes in pH, acts as a reserve and soil systems are natural buffers.
68
Soil solution(Active Acidity)-
1 of every 10,000 exchangable cations are in active phase. less than 1 lb/acre of lime needed to neutralize.
69
Soil Colloids"reserve acidity"-
2-8 tons /acre needed to neutralize .
70
Salt replacable(exchangable) acidity-
involves Al and H that are easily exchangeable by other cations in a simple unbuffered salt solution.
71
Residual Activity-
Can be neutralized by limestone or other alkaline materials but cannot be detected by the salt- replaceable technique.
72
How do soil become acidic?
Leaching of bases by water
Crop removal of bases
Acid forming fertilizers
73
Effects of soil pH on plant growth:(4)
Nutrient avalibility
Solubulity of toxic substances
effects on microorganisms
Direct effect of pH on root cells
74
Percents of base saturation 6.5-7:
5.5-6.5:
low-5.5:
80% and up
50-80%|
less than 50%
75
Liming soils:
raises pH and eliminates nutrient toxicities, deficiences and microbial activity. soils respond to lime after the pH drops below 6.0
76
Soil amendment-
anything added to the soil that improves soil chemistry without providing nutrition. ex.(lime)
77
How does lime work?
it breaks down Ca ions and Carbonic acid.neutralizing acidity.
78
Limiting agents:
CaO
Ca(OH)2
CaCO3
MgCO3
79
Application of lime-
every 3 -5 years
applied with or before the crop
not economical to apply >6tons/acre/year
Amount based on soils buffering capacity
80
Limestone quality depend on?
the neutralization value and fitness of grind, limstone quality is the product of the neutraliztion value and the fitness factor.
81
Fitness Factor-
depends on how finely the rock material is ground. smaller particles the more reactive,
82
Quality factor-
Neutralizing value X fitness factor
83
Acid rain-
Acid decomposition from the atmosphere. Nitrogen and sulfur containing gases. mostly a problem in humid forests near urbanized and industrialized areas.
84
How to reduce the effects of acid rain(3)
reduce S and N emissions
liming lakes and forests is economically limited
re-vegetation.
85
What is capable of acting as a habitat for biological organisms?
Soil
86
What is responsible for most of the chemistry that occurs in soil?
Soil organisms
87
Photosynthesis
6CO2+6H2O =C6H12O6 +O2
88
Respiration
C6H12O6+6O2=6CO2+6H2O
89
Soil macro and micro organisms are important for:(4)
Organic matter decomposition
Nutrient availability
Soil development
Plant disease
90
Prokaryotes:
Bacteria
91
How do large animals help soil develop-
enhance soil by burrowing and mixing soil
92
Earthworms
Annelida
excret casts
increase aeration and drainage
increase size and stability of soil aggregates
mixing is very important in no till system
93
Protozoa
most varied and numberous
cause animal and human disease
predators in the rhizosphere
94
Nematodes-
Microscopic thread worms or eelworms
95
Saprophytes-
organisms that live on decaying matter
96
Parasites-
infest roots causeing extensive damage to field and vegetable crops
97
predators-
prey on other microbes
98
Green plants-(3)
Vascular plant,
contribute to soil more than other living organisms combined
autotrophs
99
Soil benefits of plants-(4)
Organic matter produced when plants decompose
Root channels influence physical properties
Nutrient uptake influences soil chemistry
root decomposes influences soil organisms
100
roots-(rhizoshpere)
tiny channels are increased in size as roots swell and grow, 15-40% mass of above ground biomass.
101
rhizosphere contributes to:(4)
organic acids
amino acids and simple sugars
Mucigel
competition for resources.
102
Algae-
photosynthetic,aerobic photoautotrophs.
| needs oxygen light and moisture.
103
Fungi-
Aerobic heterotrophs, humus formation
need oxygen and organic carbon
responsible for most soil born diseases
104
Molds-
organisms of threadlike mats formed from individual strands, break down anything, low pH
105
Mycorrhizae-
symbiotic mold fungi,
fungus root symbiosis obtain c energy from roots,
act as root hairs
help supply nutrients to root.
106
Ectomycorrhizae-
external, doesn not penetrate the cortex cell walls of the root.
107
Endomycorrhizae-
enter cells
108
Actinomycetes-
resemble molds, like pH OF 6.5-7,
| Can break down complex substances.
109
Bacteria-
smallest organisms,
most diversity
unicellular form colonies or spores
110
Autotrophs-
C form CO2 ,inorganic
111
Heterotrophs-
C and energy from .
| most bacteria.(ultimate decomposers)
112
injurious effects of soil organisms:
rodents eat roots
everything else eats plants
soil born diseases, most from fungi
113
Controls of plant diseases:(6)
```
Quarantine
Eliminate crop host
Crop rotation or tillage
pH control
Steam and chemical sterilization
Plant breeding
```
114
Agriculture practices that decrease diversity:(5)
```
pesticides
erosion
monocultures
excess tillage
industrial sewage
```
115
Aig practices that increase diversity:(5)
```
Drainage and aeration
Fert and lime
manures
balanced irrigation
Erosion control
```
