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Soils > Exam 2 > Flashcards

Exam 2 Flashcards

0
Q

What are 2 categories of ways that wue can be improved

A
  • Increase water available to plants

- increase water holding capacity.

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1
Q

Define water use efficiency?

A

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

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2
Q

How might water capture be improved?

A 
A) maintain vegetation 
B) maintain organic matter on the surface.
C) reduce plowing
D) reduce compaction
E) reduce run off by land leveling
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3
Q

How might captured water be better used?

A
  • grow water efficient crops
  • reduce evaporation (mulch,reduce tillage, reduce time of bare soil
  • reduce transpiration
  • Wind breaks
  • reduce weeds
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4
Q

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

A

80%

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5
Q

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

A
  • reduce wind volocity
  • reduce tillage
  • shade soil
  • mulch & reduce weeds
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6
Q

Indicate 3 ways that irrigation water can be saved.

A
  • use an efficient system
  • determine whc (don’t overwater)
  • irrigate according to need not time
  • maintain equipment
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7
Q

Why is soil aeration important for plants?

A
  • Aerobic Respiration needs oxygen

- remove toxic gases

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8
Q

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

A
  • MACROPOUROSITY
  • water flow through the soil
  • oxygen consumption of soil organisms
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9
Q

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

A

Air exchange mostly by diffusion maybe

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10
Q

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

A
  • O2 is lower than in atmpspher

- N is about the same

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11
Q

What are the oxygen levels in the soil profile?

A

-O2 is even lower the farther down in soil profile

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12
Q

What is the role of oxygen in oxidation?

A

Oxygen Is an extreme oxidizing agent

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13
Q

Why is the reduction of O2 important for organisms?

A

.critical reaction in aerobic respiration

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14
Q

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

A

Carbon

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15
Q

Name 3 ecological effects of poor aeration?

A
  • 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
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16
Q

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

A 
Field 
-employ drainage
-maintain drainage
Potted
-minimize mineral portion of soil mix
-use tall pots
-water only when bottom becomes dry
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17
Q

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

A

Affects rate of biochemical reactions

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18
Q

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

A
  • 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
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19
Q

Discuss soil solarization

A

uses sunlight to kill microbes

20
Q

Name 2 effects from the freezing /thawing of soils?

A
  • causes expansion and contraction which causes rocks to break into soil
  • can reduce compaction and compression
  • moves objects to soil surface
21
Q

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

A

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

22
Q

Name 3 ways to manage soil temperatures

A
  • organic mulches (slow freeze slow warm)
  • plastic mulches (can trap moisture, Warm if black)
  • utilize irrigation can cool soil
23
Q

What is a soil colloid? Why is it special?

A
  • special particles,extremely small,mineral or organic

- have high electrostatic charge (highly reactive)

24
Q

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

A

-.000001

Negative in high acid soils

25
Q

Discuss the absorption of ions on soil colloids

A
  • attracts + charged ions (cations)

- holds some pesticides and contaminants

26
Q

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

A
  • crystal silicate layer (predominant)
  • non-crystal silicates
  • aluminum+ iron oxide
  • organic matter (humus)
27
Q

Of what are crystalline silicate clays composed?

A

Silicate or aluminum

28
Q

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

A

Sheets held together in groups of 2,3,or4

The number of groups and composition determines clay type

29
Q

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

A
  • isomorphaes subsituation

- breaking of the edge of crystals

30
Q

How do the charges actually develop?

A

When a colloid breaks?

31
Q

Name and describe the 3 major types of crystalline clays

A

.expanding-space between sheets

  • non-expanding-little/no space space between sheets
  • non-silicate no tetrahedral sheets??????
32
Q

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

A

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

33
Q

How are humus and mineral colloids created?

A

Humus-mostly carbonates

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

34
Q

Describe cation exchange

A

-reversible process in which a cation is substituted for another

35
Q

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

A

.usually takes place in Water

Cations are usually attached to colloids

36
Q

Detail the 4 principals of cation exchange

A

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

37
Q

Define cation exchange capacity

A

.the ability of the soil to hold or substitute cations

38
Q

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

A

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

39
Q

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

A

.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

40
Q

Why does a very low ph seem to reduce cec?

A

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

41
Q

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

A

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

42
Q

Define base saturation.

A

.% of cation exchange complex occupied by basic cations

43
Q

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

A

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

44
Q

Of what practical importance is anion exchange?

A

Indicater of excess al3+ (bad)

45
Q

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

A

Attract 2+ cations but not 1+ causing diffichancy

46
Q

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

A

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

47
Q

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

A

.evidence that DNA can be transferred to organisms

Animal antibiotics remain active in soil And may be taken up by organisms

Soils (4 decks)

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