Soils

Question 1

4 Components of Soil

Answer 1

• Mineral Matter
• Organic Matter
• Air
• Water

Question 2

Mineral Matter

Answer 2

consists of weathered parent material (rock) that has been deposited by running water, wind, or glacial ice

Question 3

Organic Matter

Answer 3

The remains of plants and animals living on, or in, the soil. Forms a distinct layer on the soil surface or be mixed with mineral matter. Lies on surface of soil where it accumulates

Question 4

Air

Answer 4

Provides oxygen used in the decay of organic matter and the growth of plants. Also dissolves soluble chemical compounds needed for plant growth

Question 5

Water

Answer 5

Transports mineral particles and soluble chemical compounds through the soil

Question 6

Properties of soil

Answer 6

Texture
Structure
Matter
Colour

Question 7

Peds

Answer 7

The tendancy of individual grains of the soil to group together to form larger units. Increases soil porosity making space for air and water in the soil

Question 8

Soil Colour

Answer 8

Humid/Tropical Regions: Red to reddish brown. Reason: Bedrock has a high iron content
Temperate Grasslands: Black to dark brown. Reason: Organic matter and humus
Coniferous Forests: Grey in upper levels and brown to yellow at lower levels
Arid: White in colour. Reason: Concentrations of calcium carbonate

Question 9

Rate of organic decay

Answer 9

Changes with temperature, the amount of water, volume of air in the soil, and the activity of soil bacteria

Question 10

Humus

Answer 10

Partly composed organic matter within a soil. Large quantities equals bronw/black colour. Humus decay releases soluble plant nutrients (nitrogen, potassium, phosphorus)

Question 11

Air and Water

Answer 11

The proportion of air in soils is controlled by soil texture and structure. The coarser the texture = greater porosity = greater activity of soil bacteria. The amounts are complementary to each other, high of one then lower of the other. Where soil pores are saturated = less growth

Question 12

Soil Chemistry

Answer 12

Fertility is closely related to clay and humus content.

- Higher the pH value, the more alkaline the soil (higher the concentration of calcium and salts)

Question 13

Soil Horizons

Answer 13

• Soils have distinct horizontal layers called “horizons” Each layer has distinct textures, colours and chemical compositions and structures
• They are created by the movement of water upwards and downwards through the soil, transporting soluble compounds and fine clay particles

Question 14

Leaching in soil

Answer 14

The process by which water removes materials in solution from one horizon to another. Greater amount of water = greater amount of leeching. Greater acidity = greater leaching effect.

Question 15

Leaching in Tropical Climates

Answer 15

Leaching occurs all year round and removes many minerals from the soil

Question 16

Leaching cooler climates

Answer 16

Winter freeze-up stops leaching action

Question 17

Leaching in arid/semi-arid regions

Answer 17

High evaporation rates lead to formation of a layer of calcium carbonate near the surface of the soil

Question 18

Caliche

Answer 18

A hard layer of calcium carbonate deposits develops in the soil

Question 19

Factors affecting soil formations

Answer 19

Climate
Organisms and Plants
Relief
Parent material
Time
Soil as a system

Question 20

Climate Factors

Answer 20

Humidity, evaportation, precipitation and the duration of sunshine

Question 21

Evapotranspiration

Answer 21

Combined processes of evaporation of water to the atmosphere and the transpiration of water by plants. (affects the amount of water available for soil formation)

Question 22

Temperature

Answer 22

Higher temps break down organic and inorganic materials. Tropical climates have more weathering than polar regions

Question 23

Organisms and Plants

Answer 23

Living organisms affecting soil development are bacteria and fungi, along with earthworms and burrowing insects and animals. Bacteria and fungi cause initial breakdown of plant and animal tissues.

Question 24

Plant influence on soil development

Answer 24

Roots open up soil, allowing water and air to penetrate the below surface. Plant tissues act as storage reservoirs for soluble nutrients that would otherwise be leached from the soil in humid areas. When plants die, nutrients are released into soil for new plants to take up

Question 25

Relief

Answer 25

Configuration of land surface affects soil formation

Steep slopes = erosion = lack of development of deep soil profiles. Level areas suffer from drainage problems

Question 26

Parent Material

Answer 26

Parent material is the weathered mineral matter from which soils originally develope
Size fragments determines soil texture, which influences the speed with which soil-forming processes operate
Also influences pH, acidic rocks have a low pH, but if the parent material forms over limestone will have a high pH

Question 27

Time

Answer 27

Soils require time to form
Young soils reflect nature of parent materials
As time passes, vegetation, climate and slope become dominant

Question 28

Soil as a system

Answer 28

Soil formation is an open system in which soil results from additions such as solar energy and water, and losses of such things as water, nutrients and soil particles through drainage, leaching and erosion