Exam 2

Question 0

What are 2 categories of ways that wue can be improved

Answer 0

• Increase water available to plants

- increase water holding capacity.

Question 1

Define water use efficiency?

Answer 1

The quality of water to produce a quantity of plant material.

Question 2

How might water capture be improved?

Answer 2

A) maintain vegetation 
B) maintain organic matter on the surface.
C) reduce plowing
D) reduce compaction
E) reduce run off by land leveling

Question 3

How might captured water be better used?

Answer 3

• grow water efficient crops
• reduce evaporation (mulch,reduce tillage, reduce time of bare soil
• reduce transpiration
• Wind breaks
• reduce weeds

Question 4

What is the extent of fresh water usage by all agriculture type entities?

Answer 4

80%

Question 5

Name 5 ways in which water can be conserved from evaporation or consumption losses?

Answer 5

• reduce wind volocity
• reduce tillage
• shade soil
• mulch & reduce weeds

Question 6

Indicate 3 ways that irrigation water can be saved.

Answer 6

• use an efficient system
• determine whc (don’t overwater)
• irrigate according to need not time
• maintain equipment

Question 7

Why is soil aeration important for plants?

Answer 7

• Aerobic Respiration needs oxygen

- remove toxic gases

Question 8

What 3 factors determine oxygen availability? Which is usually the most important?

Answer 8

• MACROPOUROSITY
• water flow through the soil
• oxygen consumption of soil organisms

Question 9

What is the primary means of movement of gas in/out of the soil?

Answer 9

Air exchange mostly by diffusion maybe

Question 10

How does the CO2 content in the soil differ from the atmosphere? N2 content?

Answer 10

• O2 is lower than in atmpspher

- N is about the same

Question 11

What are the oxygen levels in the soil profile?

Answer 11

-O2 is even lower the farther down in soil profile

Question 12

What is the role of oxygen in oxidation?

Answer 12

Oxygen Is an extreme oxidizing agent

Question 13

Why is the reduction of O2 important for organisms?

Answer 13

.critical reaction in aerobic respiration

Question 14

What other molecules discussed in class can act as oxidizing agents under low o2 conditions?

Answer 14

Carbon

Question 15

Name 3 ecological effects of poor aeration?

Answer 15

• reduces the rate of decomposition of organic matter
• the form of elements change becoming more or less available to plants.
• effects the release of green house gas

Question 16

How can aeration be maintained in the field? In container plants?

Answer 16

Field 
-employ drainage
-maintain drainage
Potted
-minimize mineral portion of soil mix
-use tall pots
-water only when bottom becomes dry

Question 17

What is the overall general effect of soil temperatures on Plant processes?

Answer 17

Affects rate of biochemical reactions

Question 18

Indicate 3 specific effects of cold (or warm) temperatures?

Answer 18

• above ground photosynthesis is effected as well as vegetation growth
• seed germination is faster when warm (some require cold temps before germination)
• root function, respiration, nutrients, and water uptake are reduced with low tematures
• microbes…lower temperatures reduce metabolism

Question 19

Discuss soil solarization

Answer 19

uses sunlight to kill microbes

Question 20

Name 2 effects from the freezing /thawing of soils?

Answer 20

• causes expansion and contraction which causes rocks to break into soil
• can reduce compaction and compression
• moves objects to soil surface

Question 21

Name 5 factors that affect the absorption and loss of solar energy

Answer 21

-albedo reflection ???
-Landscape aspect (direction hill faces)
Rain (effects ability to hold heat)
Soil cover
Soil depth

Question 22

Name 3 ways to manage soil temperatures

Answer 22

• organic mulches (slow freeze slow warm)
• plastic mulches (can trap moisture, Warm if black)
• utilize irrigation can cool soil

Question 23

What is a soil colloid? Why is it special?

Answer 23

• special particles,extremely small,mineral or organic

- have high electrostatic charge (highly reactive)

Question 24

What is the size of a colloid? What charge does it usually have?

Answer 24

-.000001 | Negative in high acid soils

Question 25

Discuss the absorption of ions on soil colloids

Answer 25

- attracts + charged ions (cations) | - holds some pesticides and contaminants

Question 26

Name the 4 types of colloids? Which is usually most abundant?

Answer 26

- crystal silicate layer (predominant) - non-crystal silicates - aluminum+ iron oxide - organic matter (humus)

Question 27

Of what are crystalline silicate clays composed?

Answer 27

Silicate or aluminum

Question 28

What can be determined by knowing the number and composition of sheets?

Answer 28

Sheets held together in groups of 2,3,or4 | The number of groups and composition determines clay type

Question 29

From where do the charges on the colloids appear? (2 places)

Answer 29

- isomorphaes subsituation | - breaking of the edge of crystals

Question 30

How do the charges actually develop?

Answer 30

When a colloid breaks?

Question 31

Name and describe the 3 major types of crystalline clays

Answer 31

.expanding-space between sheets - non-expanding-little/no space space between sheets - non-silicate no tetrahedral sheets??????

Question 32

Indicate 2 ways in which non-silicate clays differ from silicate clays

Answer 32

-no tetrahedral sheets -no silican contain fe and or al

Question 33

How are humus and mineral colloids created?

Answer 33

Humus-mostly carbonates | Mineral colloids- derive from primary minerals.general weathering followed by physical and chemical alterations

Question 34

Describe cation exchange

Answer 34

-reversible process in which a cation is substituted for another

Question 35

What is usually required to be present for exchange to occur?

Answer 35

.usually takes place in Water | Cations are usually attached to colloids

Question 36

Detail the 4 principals of cation exchange

Answer 36

-it is reversible -equivalence- charges need to balance Balance will match ratio of exchange Some cations absorb more strongly than others

Question 37

Define cation exchange capacity

Answer 37

.the ability of the soil to hold or substitute cations

Question 38

Describe the relative cec between sand silt clay and Organic matter.

Answer 38

(low) .sand < silt < clay < om (high)

Question 39

Of what valuable it to know the cec of a soil?

Answer 39

.know if soil can hold and supply essential nutrients Gives idea of Amount of nutralizing material needed Indicates ability of the soil to hold pesticides and contaminants

Question 40

Why does a very low ph seem to reduce cec?

Answer 40

Low ph = high h+ causes cec to be low due to the h+ occupying all of the negative charges

Question 41

Describe how cations are actually released from the cation exchange complex for uptake by plants?

Answer 41

Roots excrude h+ where h+ cations push nutrient cations off the cation exchange complex so plants can absorb nutrients

Question 42

Define base saturation.

Answer 42

.% of cation exchange complex occupied by basic cations

Question 43

Name 2 basic cations and 2 acidic cations? What does it tell us about the soil?

Answer 43

.basic cations k+ mg2+ ca2+ acid cation h+ al3+ nh4+ Indicate extent of weathering

Question 44

Of what practical importance is anion exchange?

Answer 44

Indicater of excess al3+ (bad)

Question 45

What is it about the roots of legumes that might create k+ deficiencies?

Answer 45

Attract 2+ cations but not 1+ causing diffichancy

Question 46

Indicate 3 facts about the bonding of biomolecules to clay and humus?

Answer 46

Binding occurs rapidly Binding ability is dependent on type of clay colloid Biochemicals attached to collies are more resistant to degregation

Question 47

Describe 2 recent issues with regards to the continued activity of certain bound biomolecules?

Answer 47

.evidence that DNA can be transferred to organisms | Animal antibiotics remain active in soil And may be taken up by organisms