Soils Quiz 1

Soil

A natural medium that supports plant growth and performs important functions.

Five major functions of soil

Plant growth

Medium for plant growth

Soil supports plants

Root ventilation

The movement of gases in soil that allows CO2 to escape and oxygen to reach roots.

Macronutrients

Nutrients plants need in large amounts.

Micronutrients

Nutrients plants need in small amounts.

Controls water movement

Soil stores and purifies water and affects nearby water quality.

Recycling of materials

The breakdown of organic waste that releases nutrients and CO2.

Humus

Dark

Habitat for organisms

Soil provides organisms with water

Engineering medium

Soil used for building materials

Bearing strength

The ability of soil to support weight.

Compressibility

The ability of soil to be compressed.

Shear strength

The ability of soil to resist sliding or deformation.

Soil stability

The ability of soil to remain stable under forces.

Four major components of soil

Air

Ideal soil composition

45% mineral matter

Mineral matter

The solid framework of soil made of mineral particles.

Sand

Mineral particles 2 to 0.05 mm in diameter that feel gritty.

Silt

Mineral particles 0.05 to 0.002 mm in diameter that feel smooth and are not sticky.

Clay

Mineral particles smaller than 0.002 mm that feel smooth and stick together.

Soil texture

The percentage of sand

Soil structure

The way sand

Colloidal properties

Properties of very small particles dispersed in a different medium.

Primary minerals

Minerals that change little in composition since soil formation.

Secondary minerals

Minerals formed by weathering and breakdown of other minerals.

Soil organic matter

Carbon-containing substances in soil

Organic glues

Substances that help soil particles stick together into aggregates.

Nutrient cycling

The breakdown and recycling of materials that increases nutrient availability.

Soil water

Water in soil that supports life and helps drive soil formation.

Soil solution

Soil water containing dissolved ions and inorganic compounds.

Plant-available water

Water in soil that plants can use.

Soil air

Air in soil pores with higher CO2 and lower O2 than the atmosphere.

Relationship between soil air and water

As water increases in soil pores