Module 12: Chemical Properties of Soil

Question 1

What are chemical components of Earth’s crust?

Answer 1

Oxygen (O)
Silicon (Si)
Aluminum (Al)
Iron (Fe)
Calcium (Ca)

Question 2

What is the percentage of oxygen in Earth’s crust?

Answer 2

46.10%

Question 3

What is the percentage of silicon in earth’s crust?

Answer 3

28.20%

Question 4

What is the percentage of Aluminium in Earth’s crust?

Answer 4

8.23%

Question 5

What is the percentage of iron in Earth’s crust?

Answer 5

5.63%

Question 6

What is the percentage of calcium in earth’s crust?

Answer 6

4.15%

Question 7

What are some macronutrients in soil?

Answer 7

Nitrogen (N)
Phosphorus (P)
Potassium (K)
Sulphur (Su)
Calcium (Ca)
Magnesium (Mg)

Question 8

What are some micronutrients in Earth’s soil?

Answer 8

Iron (Fe)
Manganese (Mn)
Boron (B)
Copper (Cu)
Zinc (Z)
Molybdenum (Mo)

Question 9

What is Nitrogen (N) and what does it do for plant growth?

Answer 9

Important for rapid plant growth, increases seed and fruit yields, enhances the value of leaf and forage crops

Question 10

What does Nitrogen (N) do within a plant?

Answer 10

Forms part of the chlorophyll and all proteins, including enzymes

Question 11

What is the purpose of Phosphorus in plant growth?

Answer 11

Plays role in photosynthesis
Used in production of oils, starches, sugars
Helps plant combat stress
Speeds up growth
Increases flowering and root production

Question 12

What is the role of Potassium (K) in plant growth?

Answer 12

Helps with protein production
Plays role in photosynthesis
Improves fruit quality
Reduces disease

Question 13

What is pH?

Answer 13

Potential of hydrogen

Question 14

What is soil pH?

Answer 14

Measure of how acidic or alkaline a soil is

Question 15

What is another term for soil pH?

Answer 15

Soil reaction

Question 16

What is the pH scale range?

Answer 16

0 to 14

pH of 7 = neutral

Question 17

How is pH determined?

Answer 17

Depends on the concentration of hydrogen ions (+ charged atoms) in the soil

Question 18

What happens when hydrogen ions increase in soil?

Answer 18

When the number of H ions in the soil goes up, the soil pH decreases and the soil becomes more acidic

Question 19

What happens when the amount of hydrogen ions in soil decrease?

Answer 19

When number of hydrogen ions decreases, soil pH increases and the soil becomes more alkaline or basic

Question 20

Why is soil pH important in plant growth?

Answer 20

Soil with suitable pH is in chemical balance and allows the plant to absorb all the nutrients from the soil

Question 21

What soil pH do most plants grow well in?

Answer 21

pH close to neutral (pH 6.6-7.4) or slightly acidic (pH 6.0 to 6.5)

Question 22

What happens when the soil pH is outside of the preferred range of the plant?

Answer 22

Plant is stressed and grows unhealthily

Fungi, algae and moss may be more suited to the pH and take over the soil

Question 23

What are some factors that affect soil pH?

Answer 23

Fertilizers (makes soil more acidic)
Rain (makes soil more acidic)
Pine needles (makes soil more acidic; good to grow rhodos)
Mulch (makes soil more acidic)
Grass clippings (makes soil more acidic)
Local manufacturing/businesses (makes soil more acidic)
Snow (makes soil more acidic)
Pets (makes soil more acidic)
Chemical treatments; pesticides, fungicides (makes soil more acidic)
Septic tanks (makes soil more acidic)
Watering; tap water (makes soil more alkaline)

Question 24

What is an ion?

Answer 24

Atom or molecule with an electrical charge

Question 25

What is a cation?

Answer 25

Ion with a positive charge (H+, NH4+, Ca++, Mg++) Gives away electrons

Question 26

What is an anion?

Answer 26

Ion with a negative charge (NO3-) Takes electrons

Question 27

What are cations typically attracted to in soil?

Answer 27

Negatively charged surfaces of clay particles and organic matter particles Clay particles and organic matter particles are naturally negatively charged, so positive ions are attracted to them

Question 28

What is the Cation Exchange Capacity?

Answer 28

Extent to which a soil could hold and exchange cations

Question 29

What is the attraction of cations in soil called?

Answer 29

Adsorption. Ions stays on the surface and are not absorbed

Question 30

Why is Cation Exchange Capacity important?

Answer 30

Soils that have a higher CEC can hold and make nutrients more likely available to plants as opposed to losing them through leaching Low CEC = nutrients leached

Question 31

How is Cation Exchange Capacity affected by soil texture?

Answer 31

The more alkaline the soil is, the higher the CEC The more organic particles and clay particles, the higher the CEC

Question 32

What two soil particles have no charge?

Answer 32

Silt and sand particles