Soil Architecture and Physical Properties

Define “hue” and list color code.

redness or yellowness (10YR)

Define “value” and list color code.

lightness or darkness (5)

Define “chroma” and list color code.

brightness (6)

What are the criteria for a well-drained soil?

30” or deeper (no grey mottles, yellow/red)

What are the criteria for a mod. well-drained soil?

18-30” (grey mottles, yellow/brown)

Criteria for somewhat poorly drained soil?

10-18” (mostly brown)

Criteria for poorly drained soil?

10-18” (mostly grey)

Sand calculation:

dry sand/total

Clay calculation:

dry clay/total

Silt calculation:

100 - sand - clay

Where can spheroidal soil structure be found?

A horizon

Where can platy soil structure be found?

E horizon

Where can blocky soil structure be found?

B horizon

Where can prism soil structure be found?

B horizon

What influence does texture and structure have on soil?

water movement

Esplain the relationship between pore space and bulk density.

as pore space increases, bulk density decreases

What causes soil crusting?

• high salt content

• drying

• closed pore space by soil particles

How can you combat soil crusting?

• soil conditioners

• organic polymers

Define a wetland.

soils that are water saturated near the surface for long periods of time

What are the three characteristics of a wetland?

• wetland hydrology or water regime

• hydric soils

• hydrophytic plants

What effects does soil temperature have on physical, biological, and chemical soil processes?

• seed germination

• root functions

• microbial processes

• freezing and thawing

How to control soil temperature?

• solar absorption

• soil moisture content

• mulches

What are the biological processes that from aggregates?

• soil organisms

• production of organic glue (non-water soluble) by microorganisms

• particle enmeshing by sticky networks of roots and hyphae

What importance does organic matter have in the formation of aggreagates?

• major agent in spheroidal formation and stabilization

• major carbon source for A, B and C horizons

What are the characteristics of an aerobic soil?

• high O2

• oxidation occurs

• 21% O2, .035% CO2, >78% N

• 400mV and up

What are the characteristics of an anaerobic soil?

• low O2

• OM breaks down slowly (no oxidation)

• same N as aerobic, lower O2, Higher CO2

• 320mV and down

What is a wetland?

soils that are water saturated near the surface for a long period of time when the temperature is high enough to be anaerobic

What are the three criteria used to define a wetland?

• wetland hydrology

• hydric soils

• hydrophytic plants

Wetland hydrology?

water in by surface runoff, seepage, and precipitation

water out by surface and subsurface flow, evaporation, and transpiration

Hydric soils

saturated long enough to inhibit O2 diffusion

reduced for a long time

exhibit accumulation of organic carbon and loss of iron, manganese, and sulfur

Hydrophytic plants

aerenchyma tissues to transport O2 to roots

adventitious roots, buttress roots, or knees

In solar absorption, what is albedo?

the reflectivity of the soil (lightness or darkness)

In solar absorption, what is aspect?

the angle the energy enters