What is soil?

Question 1

What does soil do?

Answer 1

Soil provides:

1. a medium for plant growth
2. green plants with water and mineral salts for photosynthesis
3. food and shelter for a range of organisms that live both in and on it.

Question 2

What are the components of soil?

Answer 2

1. Mineral fraction
2. Organic matter
3. Water
4. Air

Question 3

What is the Mineral Fraction?

Answer 3

The bulk of soil is made up of rock particles of varying sizes. It is the result of weathering, which causes the rock to break into smaller particles. This gives the soil texture (particle size - fine, coarse and large).

Question 4

What is Organic Matter?

Answer 4

The organic fraction of the soil is derived from the dead and decaying remains of plants and animals as well as their waste products.
When these materials are fully decomposed and no longer recognisable, they are called humus, which hold clumps of inorganic particles together called crumbs.

When microbes break down this humus, they release minerals that the plants require.

Question 5

What is Water?

Answer 5

Water is used for:

1. Support
2. A medium for the uptake and transport of mineral salts and manufactured food.
3. Assist in photosynthesis and other metabolic processes
4. Cools plants through respiration.

Question 6

What is Air?

Answer 6

Oxygen is needed for the respiration of plants and other organisms.
- Directly related to particle size; small particles pack more tightly together and leave little space for air.

Question 7

How do we find the Air content of the soil?

Answer 7

1. A known volume of soil is mixed with water of know volume.
   - It is assumed that the air in the soil will be displaced by water.
2. The difference between the final volume of the mixture and the sum of the two volumes of soil and water is assumed to be equal to the air displaced.

Question 8

How do we measure the Water content in soil?

Answer 8

A known volume of soil is dried to a constant weight in an oven not exceeding 105 degrees Celsius. The weight lost will include the water in the soil.

Question 9

What is Water - holding capacity?

Answer 9

The amount of water the soil will retain or hold on to after it has been supplied with water and allowed to drain.

Question 10

How do we test the Water - holding capacity?

Answer 10

1. A known volume of water is added.
2. When the water steps dripping, the soil will be at capacity.
3. The capacity can be measured by comparing the volume of water added to the soil with volume that drained through.

Question 11

Why are artificial fertilisers used in soil?

Answer 11

Soil may lose its ability to provide nutrients and support for plants and other organisms because of erosion and leaching or overuse.

Question 12

What are the advantages of using natural fertilisers?

Answer 12

1. They improve crumb structure, drainage and aeration.
2. They add micro-organisms to the soil.
3. They are non-polluting.

Question 13

What are the disadvantages of using Natural Fertiliser?

Answer 13

1. Bulky
2. Time consuming
3. Difficult to spread
4. Not available in large enough quantities to meet the demands of large scale agriculture.

Question 14

What are the benefits of Artificial Fertilisers?

Answer 14

1. Provide a ready supply of important nutrients.
2. Inexpensive
3. Fast acting.

Question 15

What are the disadvantages of Artificial Fertilisers?

Answer 15

1. Loss of microorganisms
2. Eutrophication
3. Acidify the soil.