Week 5 - Landscape Processes - Intro to Soils

Question 1

What chemical role do the mineral and organic components of soil have?

Answer 1

• basis for plant growth - they provide mineral nutrients essential for plant growth
• source of water - they provide water to maintain transpiration stream
• haven for symbiotic microbes
• environment in which roots grow and function (must be penetrable by roots & nontoxic)

Question 2

What physical function does soil have?

Answer 2

“It is the living skin of the planet” - a mineral froth on top of the Earth’s surface

Question 3

What biological function does soil have?

Answer 3

The basis for plant growth

Question 4

How do soils form?
What are they made of?
Why are they important?

Answer 4

• can form via in situ through weathering of rock
• may be formed on eroded & deposited sediments
• made of inorganic and organic material, with voids that may contain gas, water, organisms
• soils are fundamental to life on the planet

Question 5

Why do forest soils contain more carbon than agricultural soils?

Answer 5

• there is more organic matter/debris on the ground, decomposition of organic matters is higher in forest soils compared to agricultural soils. This means that there is more carbon travelling into the soil.

Question 6

How is soil important in construction?

Answer 6

• platform which to build on
• medium from which to build from
• storage (landfills)
• medium to be creative (pottery with clay)

Question 7

Name 2 types of mineral storage in soils

Answer 7

1. Inorganic
   - unweathered mineral crystals (Ca, K Mg, P)
   - adsorbed to surface of soil particles, many cations and anions
2. Organic
   - decomposition of soil organic matter releases carbon, nitrogen, sulfur and phosphorus

Question 8

How is water used in soil?

Answer 8

• stored and released in space between soil particles
• pore size distribution will determine water holding capacity
  i. e. too small plant cant access it, too big water travel throughs too quick to get nutrients

*important for plant growth and health

Question 9

How is air used in soil?

Answer 9

• oxygen is required for plant root function (respiration)
• soil biological activity and nutrient cycling dependent on soil oxygen
• need large diameter pores for oxygen exchange

Question 10

Are soils heterogenous?

Answer 10

Yes. Soils vary in:

• Composition; amount of minerals, organic, water and air
• Spatial - vertical & horizontal
• Temporal - time and season

Question 11

What are differences between well structured and weak structured soil?

Answer 11

Well-structured

• crumb structure at surface
• blocky structure subsurface

Weak-structured

• weak crumb structure at surface
• subsoil tending towards structureless

Question 12

What is importance of soil colour? What does it tell us?

Answer 12

Soil colour is related to the minerals present (chemical properties), aeration or drainage, and organic matter.

Iron is the most common element that effects colour (oxidation) and is red.
Aeration - how much moisture is trapped and how much absorbed.

Soil colour is an important characteristic, helps provide indicators of soil drainage and different layers of the soil.

• Bright colours and strong reds; indicate that soil, or horizon, is well drained, rarely suffers from prolonged saturation - oxidations
• Dull colours ; yellow, grey often found together in mottled horizons indicate that the soil is not well drained and does suffer prolonged saturation (high clay content, or compacted somewhere in soil profile, or structure is bad) – reduced reactions
• Blue-grey, blue-greens; are certain indication that soil is saturated for most of the year *Darker colour means more moisture.
  Precipitation of iron compounds usually orange or dull red

Question 13

What is importance of soil pH?

Answer 13

The pH tells you the acidity (concentration of hydrogen ions) and alkalinity (higher concentration of hydroxylation ion) in soil.

• Most nutrients are at their maximum availability in slightly acidic neutral or slightly alkaline soils. (range between pH 4-9)
• Also the activity of micro-organisms.
• the availability of some nutrients and toxic elements determined by pH is decreased, *At extreme pH nutrients reduced and the solubility of elements becomes toxic in plants.
• High pH binds thems, low pH makes them more available

Question 14

What is a healthy soil?

Answer 14

A healthy soil – provides for its environment – one soil isn’t going to be perfect for all environments but doesn’t make it unhealthy . Healthy soil delivers a wide range of ecosystem services suited to the environment.
It is less likely to be acidic, saline, compacted, losing nutrients or eroding

Question 15

Areas of work for soil scientist?

Answer 15

Areas of work for soil scientist:
• Teaching – educating others on soil knowledge
• Crop production – analysis of what minerals are present to determine what crops/plants can grow in that area i.e., is it nutrient rich or deficient
• Conservation – checking pollution levels, trying to conserve what we have, looking at the environment and soils suitability for animal/plant life. Preserving
• Archeology – see the present and history of the land
• Suburb Design – managing the sewerage/waste, including the drainage system. To protect the soil.
• Catchment – run-off should be minimum; more should go underground and not wasted