CH 4 FCHP Plant, Soil, & Water Relationships Quiz

Soil is composed of

• inorganic materials, along with mulch, soil conditioners, and chemicals.

• air, water, inorganic materials, and organic materials

• amendments, drainage capacity, and minerals.

• living matter, coarse texture, and sand.

Answer explanation

Soil is primarily made up of air, water, and living matter, which are essential for supporting plant life and maintaining ecosystem health. The other options include components that may enhance soil but do not define its basic composition.

Soil texture refers to the

• mineral, air, water, and organic matter in the soil.

• relative amount of organic matter in the soil.

• size of the mineral and organic particles in the soil.

• size and amount of different mineral particles in the soil.

Answer explanation

Soil texture specifically refers to the size and amount of different mineral particles in the soil, which affects its properties and behavior. This distinguishes it from other components like organic matter or water.

The particles that make up soil are

• water, air, and minerals.

• sand, silt, and clay.

• sand, gravel, and silt.

• minerals, organic matter, and microorganisms.

Answer explanation

Soil is primarily composed of particles such as sand, silt, and clay, which determine its texture and properties. These components are essential for soil structure and fertility.

Soil amendments can be used to improve

• soil texture and structure.

• weathering and compaction.

• sedimentation and cementation.

• water and nutrient holding capacity.

Answer explanation

Soil amendments enhance the soil's ability to retain water and nutrients, making them more available for plants. This directly improves the water and nutrient holding capacity, which is crucial for healthy plant growth.

Soil structure is

• the portion of soil resulting from decay of animals and/or plants.

• the way in which soil particles group together into larger units.

• a practical indicator of soil conditions.

• the measure of how well soil sticks together when pressure is applied.

Answer explanation

Soil structure refers to how soil particles aggregate into larger units, influencing water movement and root growth. This definition aligns with the correct choice, distinguishing it from other soil characteristics.

The soil property generally considered to be relatively constant and perhaps the most important physical property of soil is

• soil water.

• soil structure.

• soil texture.

• soil porosity.

Answer explanation

Soil texture, which refers to the size and distribution of soil particles, is relatively constant and crucial for determining water retention, nutrient availability, and overall soil behavior, making it the most important physical property.

The buffering capacity of a soil indicates the ability to resist

• Decomposition.

• cation exchange.

• moisture change.

• pH change.

Answer explanation

The buffering capacity of soil refers to its ability to maintain stable pH levels despite the addition of acids or bases. Therefore, it primarily indicates resistance to pH change, making 'pH change' the correct answer.

A measurement of soil bulk density is used to estimate

• Porosity.

• Friability.

• Compactness.

• texture.

Answer explanation

Bulk density is the mass of dry soil per unit volume, and a higher bulk density indicates more tightly packed soil particles, meaning greater compaction. 

Why other options are incorrect:

• Porosity:

  Bulk density is inversely related to porosity. A higher bulk density means less pore space in the soil, and a lower bulk density means more pore space.

• Friability:

  Friability refers to the ease of soil crumbling. While bulk density can be related to friability (compacted soils are often less friable), it's not a direct measure of it.

• Texture:

  Bulk density is influenced by soil texture (sand, silt, clay content), but texture describes the particle size distribution, not the degree of compaction. 

Permeability is the ability of soil to

• discharge water.

• dissolve water.

• transmit water.

• hold water.

Answer explanation

Permeability refers to the ability of soil to transmit water through its pores. This property is crucial for understanding water movement in the soil, making 'transmit water' the correct choice.

The soil color that indicates higher organic matter content is

• dark brown.

• reddish orange.

• Mottled.

• dark red.

Answer explanation

Dark brown soil typically indicates a higher organic matter content due to the decomposition of plant and animal materials, making it rich in nutrients. Other colors like reddish orange or mottled do not signify the same level of organic matter.