Module 1: Soil formation, functions and threats

Question 1

Why are soils important?

Answer 1

We rely on soils to produce food. As soil formation is a slow process (10cm in 2,000 years) it is important to preserve the soil we have.

Question 2

What are major threats to soil?

Answer 2

• loss of soil organics matter
• water and wind erosion
• sealing for urbanisation
• salinisation
• contamination, toxification, pollution
• nutrient imbalances
• soil biodiversity decline
• loss of wettability (when soil does not infiltrate, filter, or redistribute)

Question 3

How do you identify the structure and texture of soil?

Question 4

What is the ISRIC SoilGrids?

Answer 4

ISRIC is the world data centre for soil.

Question 5

How are soils formed?

Answer 5

By the following five factors discovered by Dokuchaev:
1) Parent material
2) Climate
3) Vegetation
4) Time
5) Topography
The most recently added factor:
6) People

Question 6

What are key soil functions?

Answer 6

1) Plants grow in soils for food, fuel and fibre.
2) Construction materials, e.g. wood, bricks, …
3) Foundation to life on, e.g. infrastructure
4) Water storage, quantity-, & quality management
5) An important habitat for a lot of species. 24% of the total global biodiversity lives in the soil.
6) Nutrient cycling and mineralisation (=breaking down of dead organic material).
7) Climate regulation and carbon sequestration.

Question 7

What is the FAO?

Answer 7

The Food and Agriculture Organisation of the United Nations.

Question 8

What are ‘soil ecosystem services’? + examples

Answer 8

Soil ecosystem services are the benefits we receive from soil functions. E.g. healthy food, fresh water, flood control …

Question 9

What is a lysimeter?

Answer 9

A tool to investigate the filtering capacity of the soil. It captures the soil solutions (=liquids) passing through the soil at different depths.

Question 10

What is a spiritual link to mineralisation and nutrient cycling?

Answer 10

When we die the minerals in us are eventually cycled back into the soil. Technically we are soil, just temporarily in a human form.

Question 11

What gives soils their dark brown colour?

Answer 11

The soil organic matter which is carbon locked up in the soil.

Question 12

What is soil texture?

Answer 12

Soil texture are the mineral inorganic components of the soil and their relative proportions to each other (sand, silt and clay).

Question 13

What are the main classes of soil texture? And what are their points of distinction?

Answer 13

Sand (coarse), silt (fine), and clay (fine soil). Sometimes gravel is also in the soil.

Question 14

What is loam?

Answer 14

A soil is called loam when there is an equal combination of sand, silt, and clay.

Question 15

What does the soil texture influence?

Answer 15

Water-holding capacity, permeability (infiltration rate), nutrient retention, erodibility, soil biological activity …

Question 16

What is soil structure?

Answer 16

Soil structure informs us about how the solid soil particles are arranged, meaning how they are bound together and aggregated.

Question 17

What is the difference between soil structure and soil texture?

Answer 17

Where soil texture looks are the size of the particles and their relative proportions (sand, silt and clay) soil structure looks at how the aggregates are arranged.

Question 18

What are soil peds? What forms them? What keeps them together?

Answer 18

A synonym for soil peds is soil aggregates. They can be formed by freezing, thawing, meeting, drying, fungi, roots, tillage. Clay, iron oxides, and soil organic matter.

Question 19

What are some examples of soil structures? What is the most preferable soil structure for agriculture?

Answer 19

Granular soil.

Question 20

What are soil qualities?

Answer 20

Soil texture and soil structure.

Question 21

What is soil degradation? Provide examples.

Answer 21

Soil degradation s the decline in soil chemical, physical, and biological qualities due to improper management of it, usually for agriculture, pastoral, industrial or urban reasons.
Examples are loss of soil organic matter, soil compaction, salinity, erosion, loss of fertility.

Question 22

What is land degradation and how does it differ from soil degradation?

Answer 22

Land degradation describes how land resources like air, soil, vegetation, water, climate, relief, rocks, have changed for the worst. Soil degradation is an indicator of land degradation.

Question 23

What is desertification?

Answer 23

Desertification is land degradation in drylands areas as a result of human activities and climate variation.

Question 24

What are some of the drivers, types, and consequences of soil degradation?

Answer 24

Question 25

What is a good database for general soil information?

Answer 25

SoilGrids.org

Question 26

What are the thresholds for sand content of the soil?

Answer 26

< 30% is low
30 - 60% medium
> 60% is high