4.2 Soil Formation And Erosion

Which horizon in a soil profile contains the most organic matter?

• A. O horizon

• B. A horizon

• C. B horizon

• D. C horizon

The process by which rocks and minerals are broken down by natural forces like water, wind, and temperature changes is called:

• A. Erosion

• B. Compaction

• C. Weathering

• D. Leaching

What is the primary cause of soil erosion on a deforested slope?

• A. Compaction from vehicles

• B. The absence of plant roots to hold soil in place

• C. The increase in organic material

• D. Wind currents at higher altitudes

Which soil texture has the highest water-holding capacity?

• A. Sandy soil

• B. Silty soil

• C. Clay soil

• D. Loam soil

In a typical soil profile, which layer would you expect to have the least organic material?

• A. O horizon

• B. A horizon

• C. B horizon

• D. C horizon

Which soil conservation technique involves planting along the natural contours of the land to prevent erosion?

• A. Crop rotation

• B. Contour plowing

• C. Clear-cutting

• D. Monoculture

Which soil component is most susceptible to erosion by wind and water?

• A. Sand

• B. Silt

• C. Clay

• D. Humus

Which of the following statements about soil degradation is correct?

• A. It can only be caused by natural factors.

• B. It is a reversible process that does not impact agriculture.

• C. It can result from both deforestation and overgrazing.

• D. It only affects tropical regions.

Which soil property is determined by the relative amounts of sand, silt, and clay?

• A. Horizon depth

• B. Texture

• C. Compaction

• D. Organic content

What term describes the process in which soil nutrients are washed away from the soil by water?

• A. Weathering

• B. Leaching

• C. Humification

• D. Salinization

A soil profile that is rich in iron and aluminum oxides and low in organic material is likely found in which horizon?

• A. O horizon

• B. A horizon

• C. B horizon

• D. C horizon

Which practice can help increase the porosity of soil, thereby improving drainage?

• A. Adding clay particles

• B. Adding sand particles

• C. Increasing organic content

• D. Compacting the soil

What type of weathering occurs when rock is broken down by plant roots or burrowing animals?

• A. Chemical weathering

• B. Biological weathering

• C. Physical weathering

• D. Mechanical erosion

Soil that is 40% sand, 40% silt, and 20% clay is classified as:

• A. Sandy clay

• B. Loam

• C. Silty loam

• D. Clay loam

Which soil horizon is known as the "zone of accumulation," where minerals like iron and clay accumulate from above?

• A. A horizon

• B. B horizon

• C. C horizon

• D. O horizon

A – The O horizon is the top layer with the highest amount of organic matter.

C – Weathering is the process that breaks down rocks and minerals.

B – Without plant roots, there is less structure to hold soil in place, leading to increased erosion.

C – Clay soil has the highest water-holding capacity due to its fine particles and low permeability.

D – The C horizon (closest to bedrock) typically has the least organic matter.

B – Contour plowing involves planting along natural land contours to reduce soil erosion.

B – Silt particles are fine and light, making them more prone to erosion than sand or clay.

C – Soil degradation can be caused by deforestation, overgrazing, and other human activities.

B – Soil texture depends on the percentages of sand, silt, and clay.

B – Leaching is when water carries nutrients away from the soil.

C – The B horizon often accumulates minerals like iron and aluminum and has lower organic content.

C – Increasing organic content (like compost) can help increase soil porosity and improve drainage.

B – Biological weathering is caused by living organisms such as plants and animals.

B – Loam is a balanced soil with approximately 40% sand, 40% silt, and 20% clay.

B – The B horizon is known as the "zone of accumulation," where minerals gather.