Essay Questions

Question 1

What is the significance of soil air and temperature?

Answer 1

Soil air + soil temp influence chemical + physical processes in soils.

Soil air influences: soil formation processes, soil color, the availability and uptake of plant nutrients, and the growth of all soil organisms.

Soil temp affects physical, biological and chemical processes occuring in soils.

For example, in cold soils biological decomposition is very slow, limiting the release of plant nutrients.

Question 2

What are three basic indicators for asoil to be classified as a wetland

Answer 2

1. wetland hydrology and H₂O regime
2. hydric soil
3. hydrophytic plants

Question 3

What determines the cation exchange capacity (CEC) of a soil?

Answer 3

The CEC is determined by the relative amounts of different colloids in the soil.

Question 4

What limiting materials are commonly used to decrease soil aciditiy in humid regions

Answer 4

• Carbonates
• Oxides
• Hydroxides

Question 5

List the four major types of colloids in soils.

Answer 5

1. Crystalline silicate clays
2. allphane and non-crystalline silicate clays
3. Hydrous iron and aluminom oxide clays
4. Humus

Question 6

How dos pH affect plant nutrient availability?

Answer 6

Soils pH affects the availability of most essential plant nutrients. For example, if a soil is too acidic, calcium + magnesium which are essential macronutirents (will be deficient)

Question 7

What three measurements are used to characterize salt-affected soils?

Answer 7

1. soil salinity level
2. exchangeable sodium percentage
3. sodium absorption ratio

Question 8

Discuss the food webs that occur in soils.

Answer 8

The food web is how soil organisms are involved in the disgradation of residues from higher plants. As one organism eats another, nutrients and energy are passed from one trophic level to a higher one.

First Trophic Level: primary producers (vascular plants and algage

Second Trophic Level: Primary consumers (herbivores)

Third Trophic Level: Predators that feed on Primary consumers.

Question 9

Why are mycorrhiza important to plant growth?

Answer 9

Mycorhiza are important for plant growht because they help plants obtain nutrients from the soil. Fungi are decomposers of organic compounds. Fungi are important in the production of humus and stabilizing soil aggrigates.

Question 10

Many environmental factors affect the level of organic matter in soils. Identify at least three factos that were discussed in teh text book or in lecture.

Answer 10

Vegtation

Minimum tillage

Nitrogen availability