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189.151 Soil Properties and Processes > Exam Study > Flashcards

Exam Study Flashcards

1
Q

Why is the soil important for ecological functions?

A
  • Provides biomass production
  • Provides a reactor
  • Acts as a biological habitat and genetic reserve
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2
Q

Why is the soil important for human functions?

A
  • Acts as a physical medium, serving as a base for structures
  • Source of raw material supply
  • Part of our cultural heritage (archaeology)
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3
Q

What do plants require from the soil?

A
  • Support
  • Oxygen
  • Water
  • Nutrients
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4
Q

What is aeration?

A

Aeration is the process by which oxygen enters the soil and CO2 and other gases escape.

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5
Q

What is soil fertility?

A

The physical fertility + the chemical fertility + the biological fertility. Also known as the fitness for use.

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6
Q

What is a soil?

A

The collection of natural bodies on the earth’s surface, containing living matter and capable of supporting plants.

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7
Q

What is soil texture?

A

Soil texture is the particle size distribution of the solid inorganic or mineral part of the soil i.e the proportion of sand, silt and clay within the soil.

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8
Q

How is a soil given a textural name?

A

According to the relative amounts of sand, silt and clay, and the physical location of the soil.

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9
Q

What are the two methods for soil texture analysis?

A

Mechanical analysis (in a lab) and estimation by feel.

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10
Q

What soil properties does texture affect?

A
  • Water movement
  • Aeration
  • Water retention
  • Nutrient availability
  • Ease of tillage
  • Susceptibility to compaction
  • Erosion
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11
Q

How does a soils texture affect aeration?

A

Fine textured soils are often poorly drained and have poor aeration, where as coarse textured soils have better natural drainage and aeration.

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12
Q

How does a soils texture affect water movement?

A

Water tends to move much more quickly through coarse textured soils than it does through fine textured soils.

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13
Q

How does a soils texture affect nutrient availability?

A

Sandy soils often have relatively small reserves of key plant nutrients.

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14
Q

How does a soils texture affect ease of tillage?

A

Clay soils are often difficult to cultivate.

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15
Q

How does a soils texture affect susceptibility to compaction?

A

Intermediate and fine textured soils are prone to soil compaction.

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16
Q

How does a soils texture affect erosion?

A

Soil particles that do not cohere well are at risk to erosion by both wind and water.

17
Q

What are attributes that are associated with texture?

A

Surface area, charge and shape.

18
Q

What is soil structure?

A

The arrangement and organisation of soil particles into aggregates (or peds) and the stability of such arrangement to stress.

19
Q

How is soil structure assessed in the field?

A
  • Degree of development
  • Shape
  • Size of peds
20
Q

What is good soil structure?

A
  • Smaller aggregates

- Stable aggregates

21
Q

How is structure formed in soils?

A
  • Wetting and drying cycles
  • Freezing and thawing cycles
  • Roots
  • Soil Organisms
  • Roots
  • Organic Matter
  • Iron and aluminium oxides
  • Clay particles
  • Soil Tillage
22
Q

What soil properties does structure affect?

A
  • The rate of water entry and movement
  • Water storage and retention
  • Aeration
  • Root penetration
  • Erosion
  • Productive potential of the soil
23
Q

Name some management practices that help with soil structure.

A
  • Cultivating and harvesting at the correct water content.
  • Don’t over cultivate
  • Use minimum tillage/direct drilling
  • Grow perennial pastures in crop rotation
  • Add compost to the soil
  • Add lime if required to increase pH
  • Avoid heavy traffic and stock when soils are wet
24
Q

What is porosity?

A

Porosity is the fraction of soil volume that consists of holes or voids.

25
Q

What are the three important characteristics of the pore space?

A
  • The total volume of pores
  • The size distribution of pores
  • The continuity of pores
26
Q

What is a micropore?

A

A smaller pore, smaller than 30um in diameter.

27
Q

What is a micropore?

A

A larger pore, bigger than 300um in diameter.

28
Q

What do the larger pores provide?

A

Aeration and drainage.

29
Q

What do the smaller pores provide?

A

Holds water.

30
Q

What is bulk density?

A

The density of an oven dried soil sample.

31
Q

What is gravimetric water content?

A

The mass of water relative to the mass of oven-dry soil.

32
Q

What is volumetric water content?

A

Volume of water relative to the total soil.

33
Q

What is the soil moisture content important for?

A
  • Determining irrigation requirements, assisting irrigation management
  • Measuring the effectiveness of drainage systems
  • Identifying the best timing and method of cultivation

189.151 Soil Properties and Processes (2 decks)

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