Deck 5: Soils

Question 1

What is field capacity of a soil?

Answer 1

Field capacity is amount of water that is left behind in the soil after excess water has drained off. Water is drained off due to the action of gravity. Water and air content of soil is ideal for plant growth at field capacity. This process usually takes place around 2-3 days after rail or irrigation. The soil moisture for various soils at field capacity is around 15 tO₂5% for sandy soil, 35 tO₄5% for loam soil and 45 to 55% for clay soil. Field capacity is also known as drained upper limit.

Question 2

What is soil pH and what is the pH range that most plants can grow in?

Answer 2

The measure of acidity or alkalinity of soil is known as soil pH. pH is the negative logarithm of hydronium ion (H + ) in solution. It decreases when hydronium ions increases in soil and vice versa. Soil pH affects the availability of plant nutrient by controlling the chemical forms of nutrient.
Soil present in areas where heavy rainfall occur or having humid environment are more acidic or having low soil pH as compared to soil in arid region. Soil pH is not the fixed characteristic of soil, it changes over time depends on the various conditions. It is measured by pH meter. The best ph range at which most plants grow is 5 to 7.

Question 3

What is parent material?

Answer 3

Parent material is the geological material formed from breakdown of rocks by weathering. It makes up a soil which is accumulated as unconsolidated deposits and consolidated rocks. This unconsolidated deposits i.e. river alluvium, volcanic ash, and organic matter later gets differentiated into different layers known as horizons. Characteristics of soil depend on type of parent material.
Various rocks form different type of soil like dark coloured ferromagnetism rocks form heavy mineral rich soils, granite rocks form loamy soil and basaltic rock form loam or clay loam soils texture. Weathered parent material is also known as saprolite. The degree of weathering required for parent material depends on various environmental factors like temperature, oxygen presence, and rate at which water percolates, surface area and mineralogy of parent material.

Question 4

How does cation exchange capacity (CEC) influence a soil's ability to hold the positively charged plant nutrients such?

Question 5

What is a soil horizon? What is a soil profile?

Question 6

What are saline and sodic soils?

Question 7

What is physical weathering?

Question 8

What are the ways that soil organisms act on the soil?

Question 9

List the four processes of chemical weathering.

Question 10

What do plants get from the mycorrhiza relationship? What do legumes get from Rhizobium ? What do the mycorrhizia fungi and the Rhizobium get in return?

Question 11

Why are soils that are formed in regions of very high rainfall or very low rainfall usually not productive?

Question 12

What does the decomposition of organic matter provide for plants?

Question 13

How do plant roots add to the organic material in the soil?

Question 14

What is humus and how does it affect soil characteristics?

Question 15

What role do bacteria and fungi play in soil formation?

Question 16

What is C:N in terms of a soil characteristic?

Question 17

What are mycorrizha and how do they help plants?

Question 18

Along with erosion, what is another factor that contributes to soil degradation?

Question 19

What kind of topography promotes water erosion? Wind erosion?

Question 20

How do plants influence erosion?

Question 21

What would you say to someone who says we should not worry about global warming because we can just start growing our grain belt crops (growing in prairie soil) farther north in the humid regions where the conifer forests now grow in Alaska?

Question 22

Even though some deserts have been in existence for thousands of years, why is the soil there considered to be very young?

Question 23

What are the five basic components of soil?

Question 24

In which soil horizon are the most roots and biological activity found?

Question 25

Mycorrhiza are now available for some crop plants. Do you think it would be worth it to a grower to purchase these?

Question 26

What is soil texture and what are the components that contribute to a soil's texture?

Question 27

How does pore space relate to a productive soil?

Question 28

What is soil structure?

Question 29

During difficult economic times, many municipalities cut back on public services. What would you tell a city council that is considering stopping the pickup of vard waste that is used to create organic compost to improve soil in the city parks?

Question 30

What are the differences between mollisols, spodosols, and oxisols?