Soil

Question 1

What are Edaphic Factors?

Answer 1

• abiotic factors relating to the physical or chemical composition of the soil found in a particular area

Question 2

What is Soil?

Answer 2

• the material found on the surface of the earth that is a complex mixture of minerals, water, air, organic materials and organisms that are decaying remains of once living things.

Question 3

Why is Soil important?

Answer 3

• soil is important because they are useful for plants.
• plants need soil for anchorage, nutrients like potassium, nitrates and salts, water and air which is also important to the organisms living in the soil like earthworms.

Question 4

Why are organisms important to soil?

Answer 4

• they are important because they create burrows in the soil that help with the physical organization of the soil and there droppings also help to fertilize the soil.

Question 5

How is soil formed?

Answer 5

• soil is made from rock
• rocks are weathered by environmental elements such as wind, water, freezing and thawing and broken down into smaller particles called rock waste
• rock waste then becomes colonised by lichens, mosses and various types of plants
• these plants and animals die and decay and their remains provide organic material for the mineral composition of the soil
• because colonisation takes a long time, good soil takes thousands of years to form

Question 6

What are the different types of soil?

Answer 6

• clay soil
• sandy soil
• loam soil

Question 7

What are the properties of Clay Soil?

Answer 7

• very small particles
• poor aeration because particles are tightly packed together
• good water holding capacity because of capillarity
• poor drainage because capillarity therefore gets water-logged easily
• holds alot of mineral ions because of attraction to clay particles

Question 8

What are the properties of Sandy Soil?

Answer 8

• very large particles
• good aeration because particles are loose
• poor water holding capacity because the particles are loose
• good drainage because the particles are loose
• not a lot of minerals because they are drained out with water

Question 9

What are the properties of Loam Soil?

Answer 9

• a mixture of both sand and clay particles
• moderate aeration
• moderate water holding capacity
• moderate drainage
• contains an adequate amount of mineral ions and nutrients

Question 10

What are the three main layers of soil?

Answer 10

• topsoil
• subsoil
• bedrock

Question 11

What is a Soil Profile?

Answer 11

• a soil profile is a vertical cross-section of soil that allows you to see the different constituents that make up the soil.

Question 12

How is a Soil Profile formed?

Answer 12

• when soil is added to glass jar and water is poured, when allowed to sit for a while, the soil will settle into different layers
• this happens because of particle size and density
• the bigger particles are more dense than the smaller particles so they will settle to the bottom while the smaller ones being less dense will settle towards the top.

Question 13

What is Topsoil?

Answer 13

• the uppermost layer of soil
• it contains the highest concentration of organic material and microorganisms

Question 14

What are the six main constituents of topsoil?

Answer 14

• living organisms
• water
• air
• nutrient ions
• mineral particles
• humus

Question 15

What is Humus?

Answer 15

• dark, sticky material formed from the breakdown of dead plants and animals and other organic matter such as faeces
• the organic matter is broken down by bacteria, fungi and organisms like earthworms

Question 16

Why is Humus useful?

Answer 16

• it contains minerals
• minerals are held together because of the sticky composition
• it improves crumb structure
• it formas clay humus complexes that improve soil stability
• it has a dark colour which gives it warming capabilities
• can make the soil more acidic
• it is food for organisms like earthworms

Question 17

What is Bacteria’s function in soil?

Answer 17

• they help to breakdown organic matter into a dark, sticky material called humus.

Question 18

Why are Earthworms important to soil?

Answer 18

• they help to make burrows in the soil which help with aeration and drainage
• they eat the soil and mix it with mucus in their guts then excrete the waste which helps to improve soil crumb sructure
• they also add humus to the soil by pulling dead leaves into the soil, excreting waste and organic material when they die

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Question 19

Why is water important to the soil?

Answer 19

• for the growth of plants and organisms like fungi and bacteria
• it is the world’s best solvent
• they produce salts readily with chemicals in the parent and they are take up to the plants by their roots

Question 20

What are extreme conditions that come with water?

Answer 20

Flooding - when all the available space in the soil gets taken up by water so it rises above the topsoil

Water-logging -

Question 21

Why is air important to soil?

Answer 21

• needed for growth of plants, bacteria and earthworms
• needed for plants, micro and macro organisms to respire

Question 22

What are mineral nutrients?

Answer 22

• elements or compounds that are either bound chemically to clay particles or dissolved in water.

Question 23

Why do plants need mineral nutrients?

Answer 23

• for growth and repair of their cells
• for certain chemical reactions to take place

They obtain their nutrients through diffusion or active transport.

Question 24

Soil Temperature

Answer 24

• water is slow to attract heat which means that wetter soils are harder to heat up than dry soils.

Question 25

Soil pH

Answer 25

• soil pH is the meaure of acidity in the soil
• plants need a certain pH to grow well and organisms like earthworms and bacteria thrive in neutral or near-neutral environments
• the pH in soils range from 4-9