soil science midterm exam

_ is the upward movement of water through soil micropores due to adhesive and cohesive forces.

Capillary action

What are two types of pore spaces in the soil?

Macropores & micropores

False answer

The temperature in a deeper soil profile fluctuates more than on the surface

True answer

Soil temperature affects the physiological processes of plant roots and animals inhabiting

the soil.

False answer

The organic components are living organisms and inorganic materials

The relative volume of solid minerals, water, air, and organic matter in a medium-textured

(loam soil) is _, _, and _, respectively.

45%, 25%, 25%, and 5%

Clay is negatively charged; therefore, __ in the soil solution are attracted to The clay

Cations

Which one of the following is true?

A- Cations replace each other on the surface of clay

B- Roots exude hydrogen ions (H+) to the soil

C- Roots absorb Ca, K, and Mg cations from the soil.

All the above

Which one of the following is false?

a. Chemical reactions take place on the surface of clay particles.

b. The greater the surface area of a particle, the greater the rate of chemical reactions

c. The surface area of a gram of clay is smaller than that of a gram of sand and silt

d. All the above

C- The surface area of a gram of clay is smaller than that of a gram of sand and silt

Which one of the following is false about soil bulk density?

a. High bulk density indicates that a soil has limited pore space

b. Water will drain easily from soil with high bulk density

c. A drainage system is installed if the soil with high bulk density is to be used for growing

plants

d. All the above

B- Water will drain easily from soil with high bulk density

The moisture content in a soil is measured using a

Tensiometer

True or false- Plants cannot absorb tightly bound water from the surface of sand particles.

False

True or false- Higher porosity indicates the soil has more space for air and organic matter

True

True or false- Sandy soil has more macropores than micropores

True

True or false- Plants absorb water from the soil by their roots

True

True or false- Most chemical reactions in soil involve clay and organic matter

True

True or false- Plant roots absorb water at permanent wilting point.

False

True or false- Metric potential is measured in kilopascals (kPa).

True

True or false- In well-drained soils, the macropores are filled with water, and the micropores

are filled with air.

False

• Marcos- air

• Micros- water

True or false- Soil macropores are those larger than 0.06 mm in diameter

True

True or false- Lower suction or tension indicates moist soil, whereas higher suction indicates

drier soil.

True

Water that is not available to plants

Hygroscopic water

Plant available water

Water between FC and PWP

Water that drains freely

Gravitational water

Water held against gravity

Water at field capacity

The amount of soil pore space

Porosity

Cohesion

attraction between water molecules

Gravel

greater than 2.0 mm in diameter

Sand

Between 0.05-2.0 mm in diameter

Silt

0.002 – 0.05 mm in diameter

Clay

Less than <0.0002 mm in diameter

Bulk density

Soil compaction

The bulk density of an ideal soil

around 1.3 g/cm3

Saturated soil

0 kPa