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Soil management > Soil water balance > Flashcards

Soil water balance Flashcards

1
Q

Structure determines

A

Porosity
Bulk Density
Pore continuality
Pore size distribution

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2
Q

3 modes of structural decline

A

OM linked Decline (stubble burning or cultivatio = loss of structure in surface layer

Dicline linked to a chemical problem (sodicity) = hardsettining

Decline due to cultivation of vehilce traffic

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3
Q

Physical degradation symptoms (4)

A

Crusting
Compaction
Hardsetting
Erosion

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4
Q

Physical degradation leads to

A 
Retarded emergence
Greater reistance to root penetration
Poor heat exchange
Poor water infiltration
Poor gas exchange
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5
Q

Ramifications of physical degratation

A

Loss od OM
Loss nutrientsRestricted traffic
Loss production area
Desertification

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6
Q

Pore space affects

A 
Infiltration
Water distribution
Air movement
Nutrient movement
erosion
storage
drainage
= influence productivity
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7
Q

2 types of pores

A

Structural /Macro
(pore space between soil grains)

Textural/matrix

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8
Q

Texture vs structure:

Structure

A

Affected by management

Vulnerable to mechanical destruction

Unstable

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9
Q

Good Structure

A 
Water stable aggregates- 1-10mm
Sufficienct pores >0.75mm for aeration
0.2-30 miromill for water holding
Little resistance to root penetration
Good infilration, water and nutrient retention
Resists erosion
Easy to work
Absence of crusting
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10
Q

Poor Soil

A 
Crusting
Erosion
Compaction
Root root penetration
High density
Poor aeration
Poor water holding
Poor nut retention
Poor
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11
Q

Evaluation of Structure

A

Bulk density
Hydraulic Conductivity
Aggregate stability
Penetration resistance

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12
Q

Aggregate Stability

A

Ability of soil aggregates to resist disintegration when disruptive forces applied -tillage, wind, water

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13
Q

Why is Aggregate stability important

A

Water infiltration
Root Growth
Resistance to erosion

Unstable aggregates= disintegrate during rain
Dispersive soil fills surface pores, hard crist develops once it dries

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14
Q

Infiltration reduced =

A

increase run off, water erosion and decreased water available

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15
Q

Aggregate stability is a function of:

A 
Clay content (kaolinite dispersicve)
CEC
Level of organic sunstances for bonding
Ca= flocculation
Na, Mg= dispersive, unstable to wetting
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16
Q

OM/OC

A

Increased OM = Inc. structure

O C is food for microorganisms = Inc. soil structure due to binding particles

17
Q

Increased Clay %

A

= Inc. OM needed for stability

Aggregatin affects susceptibility to rain drop impact, surface sealing and erosion

18
Q

3 Types of Organic Polymers

A

Transient - micro aggregation
Tempory - macro aggregation
Persistent - micro aggregation

19
Q

Transient

A

Organic material rapidly decomposed by microorganisms

Additoins of plant and animal residues that are rapidly produced and rapidly decomposed

20
Q

Tempory - macro aggregation

A

Partly decomposed material of plants or microbes
1) roots - decomposable litter, food source of microbes
2) Hyphae
>250micron
Affected by management but can still last months-years

21
Q

Persistent

A

Consists of extensively degraded Organic fragements

Roots, Hyphae, Bacteria

<250micron aggregates
Insentive to management

22
Q

Factors affecting OC

A 
Soil Management
Plants species/crop selection
Residue management
Soil and nutrient loss
Climate
23
Q

Cultivation

A

Physically disturbs soil, mixing upper and lower layers

Dec. OM
Inc. BD
Changes way particles are bonded
Inc. erosion potentia;

24
Q

Disk plough

A

Bury layer of OM built up, exposing layer of low OM at surface

25
Q

Tillage Effects on Soil Properties

A 
Aggregation
Porosity %
Infiltration capacity
BD
Soil Fauna
Soil Moisture
Soil Temp
26
Q

Tillage effects on soil processes

A 
Crusting
Compaction
Aeration
Erosion
Leaching 
OC mineralisation
Evaporation
27
Q

Tillage effects on crop Growth

A

Root development
WUE
NUE

28
Q

Conventional Tillage, Stubble removal, Burning =

A

Dec. soil C

29
Q

2 practices to decrease soil structural decline

A

Crop / parture rotation

NT/RT

30
Q

Conservative Farming

A

Dec. tillage, increased platn residues = conserve soil, water and energy

31
Q

Stubble buring

A

COntrols weeds and disease

32
Q

Retention of residues is important

A

Protects soil surface
Decreases erosion by minimising rain drop impact
COntributes to OM

33
Q

Tillage effects

A

High rate of microbial breakdown due to:

  • Shatters macro aggregates
  • Mixing surface soil
  • Increases intensity of wet/drying cycles

Movement of soil C deeper into profile = microbial breakdown

34
Q

Increased infiltration with NT due to (4)

A

Residues protecting soil against impact of rain

Minimising soil dispersion and surface sealing

SOil biopores open to surface - roots, worms
Non disturbance = continuous soil pore system = infiltration

35
Q

Conventional Tillage

A

Inverts soil and alters nature of sturcture

COntrols weeds

Looses compacted soil

Incorporates residues

Temporarily dec. BD

Inc erosion

Decreased structure

Dec. microbial activity = dec agg stability, inc crusting and surface sealing

Large pores created by tillage collapse readily becasue of soil recompaction, consolidation and decrease in soil Organic binding agents

36
Q

MT or NT Pros

A

30% residue cover

Dec BD in clong run

Increase aggregate size in duplex soils

Increase number and size of interconnected pores

Increases earthworms

Increased water retention

Increased saturated hydaulic conductivity

Increased yield

37
Q

NT cons

A

Increased run off due to less roughness

Higher deep drainage = nut loss to groundwater

Weeds and herbicides = her resistance

Soil management (3 decks)

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