Soils Exam 1

Compared to a similar soil under native vegetation, a soil with long history of conventionally tilled cropping would have less micropore space.

False

For any soil in which it is present, the C horizon is the parent material for the B horizon.

False

Proper timing of tillage is generally more difficult for a clayey than for a sandy soil.

True

Soil air usually has a higher carbon dioxide content than the air in the atmosphere.

True

Soils of good tilth and high productivity are usually characterized by stable aggregation and a high percentage of macropores.

True

The average residence time for water in clouds over the ocean is about one year.

False

Where organic matter constitutes only 1 or 2 percent of the soil by weight, it has only negligible influence on soil properties.

False

unsaturated water flow

Occurs on soils that are at field capacity

This is the most general category in the classification of soils in the United States.

Order

Water will move from one site in a soil with a water potential of -5 kPa to an adjacent site with a water potential of -40 kPa.

True

What part of the country are you likely to find the majority of the Mollisols?

Upper Midwest

Alfisols

have an argillic horizon AND is the most common soil order found in Arkansas

The plasticity index is the difference between the plastic limit and the liquid limit.

True

Which of the following pH values represents the most acid conditions?

1.0

Which of the following pH values represents a neutral condition?

7.0

The soils that are classified as 'udalfs' are in which soil order?

Alfisols

Silicate clay accumulation is most common in the _____.

B horizon

Which soil order has the least developed soils (youngest)?

Entisols

A soil developed in transported parent materials will likely have properties related to the properties of the rock below the C horizon.

False

Sandstones are good examples of metamorphic rocks.

False

Soil, like concrete and steel, is a standard construction material. Its properties are well characterized and predictable so that standard building foundation designs can be used uniformly at all building sites of a given topography.

False

Soils developed in wind-blown parent materials such as loess are generally of little agricultural value.

False

Some 60% of the water that is actively involved in the hydrologic cycle worldwide is found in soils.

False

Sprinkle irrigation is generally more efficient in the use of water than drip irrigation, especially for high value crops.

False

Subsoil is typically equivalent to the O horizons.

False

The property of cohesion in water stems from the attraction of water molecules for soil solids.

False

The topmost horizon in most humid region forest soils is the A horizon.

False

Which type of soil structure is typically found in surface soils (A horizons)?

Granular

Information about conditions at 2 to 4 meters deep in a soil usually most helpful for understanding?

How best to design a building foundation.

Using a textural triangle chart, it can be determined that a soil with 45% sand and 20% clay belongs to the _____ textural class.

Loam

Practices that add organic matter and reduce tillage can be expected to most significantly increase the ______ in a soil.

Macropores

The percentages of which soil components represent the minimum information necessary in order to determine the textural class of a soil?

Silt & Sand

Vertisols

Soils with high content of shrink-swell clays.

Gelisols

Soils with permafrost

Climate influences not only the rate of weathering by the type of native vegetation dominant in an area.

True

Which of the following locations in the United States would have the highest evaporation (E) from the soil surface in July?

a furrow-irrigated cotton field in Arizona

For which substance would the particle density equal the bulk density?

a quartz pebble

The water in the soil typically differs from pure water because the soil water _____.

all of the above

Mollisols

dark colored soils of the prairies

Capillarity in soils _____.

involves both adhesion and cohesion.

Residual parent materials are best described as _____.

materials formed by weathering of rocks and minerals in place

Igneous rocks can best be characterized as:

rocks formed when molten magma solidifies

Alluvial fans are usually characterized by _____ soils.

sandy and gravelly

Fungal hyphae have an important influence on soil structure because they ______.

stabilize macro aggregates

Most (usually 80% or more) of soil potassium and calcium can be found in the form of _____.

structural components of minerals

Plant transpiration efficiency at a given location is markedly influenced by ______.

the plant species being grown and Fertilization practices used

Which of the following statements is not correct?

tropical forests protect the soil from excessive weathering

In which of the following situations would you expect downward movement of soil water through the profile to be most rapid?

uniformly textured sandy loam profile