chapter 14

Which soil horizons are most prone to erosion?

A and O

Which of the following two regions have the largest land areas with extensive soil damage?

Africa and Asia

Soil is composed of:

All of these

Which of the following may affect the mineral composition of soil?

All of these

Loam:

All of these choices are correct

Mulch:

All of these choices are correct

The desertification of the Sahel is caused by:

All of these choices are correct

The ____________ is a lighter-colored soil layer where iron and aluminum often accumulate.

B horizon

The ____________ contains weathered pieces of rock and is found just above the solid bedrock.

C horizon

Which of the following sequences is in the correct order from largest particle size to smallest particle size?

Gravel > Sand > Silt > Clay

Why is clay particularly important in determining many soil characteristics? I. clay particles have the smallest surface area relative to other soil particles II. each clay particle has negative electrical charge on its outer surface to attract mineral ions III clay is the most porous of the soil particles IV. clay is the largest of the soil particles

II

Rank the relative size of soil particles from smallest to largest. I. sand II. clay III. gravel IV. silt

II - IV - I - III

Crop rotation and strip cropping alternate crops such as corn and wheat. The difference is:

In strip cropping, the crops are alternated by row. In crop rotation, the crops are alternated by years

Which of the following statements about minerals in soil is true?

Negatively charged mineral ions are often washed out of the root zone

_________ describes the pathway of various nutrient minerals or elements from the environment through organisms and back to the environment.

Nutrient cycling

The uppermost layer of soil that is rich in plant litter and other organic material is the:

O horizon

Which of the following authorized the formation of the Soil Conservation Service (now called the Natural Resources Conservation Service)?

Soil Conservation Act of 1935

Compost is:

a natural fertilizer

An important plant to use in crop rotation because of its association with nitrogen-fixing bacteria is:

alfalfa

A(n) __________ is a type of soil that forms in temperate deciduous forests, has a highly leached A-horizon, and must be fertilized if cleared for farmland.

alfisol

Organic fertilizers:

can consist of manure, crop residues, or bone meal.

The difference between compost and mulch is:

compost is mixed into soil to improve fertility; mulch is placed on soil's surface to control weeds and retain moisture

Increased soil erosion may be caused by all of the following except:

construction of shelterbelts

Which of the following outlines a typical crop rotation planting schedule?

corn → alfalfa → oats → soybean

Humus is composed of:

decomposed organic matter.

Clay content is particularly important in soil because high-clay soils:

have large surface areas that can "hold" mineral ions for plant use

The deposition of leached material in the lower layers of the soil is called:

illuviation

In soil, the smallest particles (less than .002mm) are called:

illuviation particles

Planting the same crop year after year:

increases damage by insects and disease

Soil with a pH of 6.0:

is slightly acidic

Scientists know relatively little about the roles of most soil organisms because

it is hard to study them in a natural environment

A major problem with conservation tillage is:

it requires greater use of herbicides to control weeds.

The removal of dissolved minerals from the soil as water moves downward is called:

leaching

Which of the following represents an "ecosystem service" performed by soil organisms?

maintaining soil fertility by decaying and cycling organic materia

Soil erosion:

may result in decreased water quality for fishes and other aquatic organisms

The richest farming soils that form under the grasslands of central North America and under moist deciduous forests are the:

mollisols and alfisols

Legume plants like soybeans add which of the following to the soil?

nitrogen

Which of the following is not true of conservation tiling?

over 70% of US farmland was planted using conservation tilling in the early 2000

A(n) _________ is a type of soil that forms in tropical and subtropical regions where organic material decomposes so fast there is very little A-horizon.

oxisol

Worldwide, 75 billion metric tons (83 billion tons) of topsoil is lost annually, primarily due to:

poor agricultural practices

Soil degradation is primarily attributed to:

poor agricultural practices, overgrazing and deforestation

The 1930's Dust Bowl in the western United States is an example of:

prolonged drought and accelerated wind erosion caused by use of marginal land for agriculture

Of the following, which has the greatest permeability?

sand

Water tends to drain rapidly through soil that is high in:

sand

Soil pH is important because:

some mineral ions are leached more easily from an acidic soil

A(n) ___________ is a type of soil that usually forms in colder climates beneath coniferous forests and makes poor farm land because it is often too acidic and nutrient poor.

spodosol

Which of the following is a type of contour plowing?

strip cropping

The soils of tropical rain forests tend to be nutrient-poor due to:

the fact that nutrient minerals are stored primarily in the vegetation

The American Dust Bowl was caused by all of the following except:

the poor (nutrient) quality of the soil of the Great Plains

Soil is formed from parent material by biological, chemical, and physical:

weathering processes.