Soil 365 Exam 1

Includes physical, chemical, and biological properties. Also includes soil quality indices.

What are the six basic functions/values of soil?

W.H.E.W.A.P.

Water storage and cleaning

Habitat for soil organisms

Engineering medium

Waste recycling

Atmospheric modification

Plant medium

Why is soil science widely unknown and undervalued? (5 adjectives)

I.D.U.U.S.

Inconspicuous

Dynamic

Ubiquitous

Underestimated

Subjective

What are the three major types of global soil degradation?

Erosion, soil organic C change, and nutrient imbalance.

What are the three major causes of soil degradation?

Population growth (agriculture), economic growth (deforestation, overgrazing), and climate change.

How might a clear definition of soil quality help decrease degradation?

A clear definition would inspire action. Without knowledge or perception, values cannot grow.

What is soil quality?

Soil quality is the combined function of soil chemical, physical, and biological properties that support the health of soil microorganisms, plants, animals, people, and ecosystems through improving water, air, and nutrient quality.

What are the 5 physical properties of soil?

Color, texture, structure, density, and water movement.

What is color?

Color is the way soil reflects or emits light.

Why is color important?

It tells us organic matter, wetness, and parent materials.

How is color measured?

Munsell color book or reflectance meters (IPhone, Nix pro, or reflectance meter).

How do we interpret SOM and wetness from color?

Low Munsell values mean higher SOM. Lower chromas mean more wetness.

What is texture?

The percent of sand, silt, clay particles and coarse fragments.

Why is texture important?

It relates to water holding, nutrient supply, and tilth, and is a factor in aggregation.

How is texture measured?

Feel, hydrometer.

How do we interpret texture as it relates to water holding and nutrient availability?

More clay means more water retention, nutrient exchange, and aggregation. More sand means the opposite (porosity).

What is structure?

The arrangement of soil separates into aggregates.

How is structure measured?

Slake test or visual assessment.

What do structure type and grade mean?

Type means what shape (GR, SKY or ABK, etc.), grade means how defined the shape is.

Why is structure important?

It’s responsible for aggregation, which influences porosity, and tilth for plants and mircorganisms.

How are the slake and wet aggregate stability tests interpreted?

The less that slakes off in water, the better the aggregate strength (%).

What is density?

The integration of texture and structure. A ratio of mass to volume of solids and pores. (M/V).

Why is density important?

For compaction and properties affected by it.

How is density measured? Unit?

Penetrometer, kPa or PSI.

How is density interpreted?

The higher the penetration resistance, the denser the soil.

What is water infiltration versus conductivity?

Infiltration is the rate of water into soil.

Conductivity is the rate of water through soil.

What is water availablility?

The amount of water by volume or mass held in the soil by tension.

Why is soil water important?

It integrates many properties and is critical for biological activity.

How is water flow measured?

Ring infiltrometer or permeameter.

How is water flow interpreted?

Sandy soils mean the most water flow. Compacted clay means the least.

How is water content measured?

By calculating a percentage of the oven-dry mass.

How is water tension measured?

Tensiometer, etc in the lab.

How is available water content interpreted?

The percent PAW should not exceed field capacity or dip below permanent wilting point.

Which soil physical properties are most static?

Texture

Which soil physical properties are most dynamic?

Bulk density, water flow