AGRY 255 Study Set

Munsell System

system used to help define the colors that we see

Hue

tint

Value

lightness/darkness

On left side of chart

Chroma

intensity/brigthness

On bottom of chart

RED,BROWN,TAN,YELLOW

OXIDIZED OR FERRIC IRON

WELL DRAINED

GREYS

NOT MUCH IRON

NOT WELL DRAINED

Organic Matter Color

Very Darkish Color

Absence of Organic Matter COLOR

Very grayish and dry

Sand Particle Size

0.05mm-2mm

Silt Particle Size

0.002-0.05mm

Clay Particle Size

Less than 0.002mm

Textural Triangle

Broken down into mainly three zones Sand/Silt/Clay

Texture

Size of the Soil Particles

Structure

manner in which the soil particles are aggregated together

PEDS

Particles aggregated together from distinct structural units

Granular

Very Porous and crumb like

Platy

Looks like plates stacked on top of each other and smushed

Subangualr

They are more circle shaped rocks

Angular

They are shaped more jagged and like cubes

Prismatic

Just like angular except they extend a lot longer

Single Grained

Particles are not aggregated

Massive

Large Cohesive Masses

O

Organic Matter

A

Mineral mixed with humus

E

Elevation of Clays

Metallic Iron

Fe^0/ Silvery White/Grayish

Iron Oxides Fe2O3

Fe³+/. Brownish Color with some Red/. Looks Like Rust

Oxides submerged without air

Fe²+/ Light Tan/Yellowish Color

Poor Aeration

Poorly Drained

Iron is in a more reduced Form

FE^++ (Ferrous)

Dull Gray Colors

Good Aeration

Well Drained

Iron is in a more Oxidized Form

Fe^+++ (ferric)

Bright Colors (Yellow, Browns, Reds)

Importance of Soil Temp

Effects Biologic Activity

Impact of Mulches

Management Practices useful for Manipulating Soil Temp

Clear Plastic=Greenhouse Like

Black=Traps heats to help keep weeds out

Plant Residues and Mulches=Slow Down Rate of Temperature

Examples of properties: Water Content/Soil Color

Macropores

Allow Rapid Movement of Water and Air

Sand

Micropores

Hold water and store it

Silt

Biopores

Tubular/contious in length

Three Effects of Poor Aeration

Decrease the rate of biologic Activity

Root growth of most plants is curtailed

Aborption of nutrients and water is lessened

Well Drained

No gray mottles above 30

Moderately Well Drained

Gray Mottles above 30 but not above 18

Somewhat Poorly Drained

Gray Mottles above 18 in brown background

Poorly Drained

Mottles extend above 18 and mostly grey

Step One of Textural Anylaysis with Hydrometer Method

Sample Size 50g

Remove OM with Hydrogen Peroxide leaving only sand, silt, and clay

Step Two of Textural Anylaysis with Hydrometer Method

Chemical Dispersion with sodium hexametaphosphate. NA+ replaces the Ca++ on the negatively charged clay particles while the phosphates form a complex with Ca

Step Three of Textural Anylaysis with Hydrometer Method

Mechanically disperse the sample in a blender or shaker

Step Four of Textural Anylaysis with Hydrometer Method

Suspend the dispersed soil in a cylinder of water, shale and then allow particles to settle

Builk Density and Pore Space

As BD increases amount of pore space decreases

The affect Time as on soil formation

Soil will change over time

Weather Rock and material can decay overtime

What happens to soil as it ages

Soil will change over time

Rocks will become weathered resulting in a Horizon

The moisture will also affect what will happen to the soil

What does nutrient recycling do for the plants

When dissolved materials are able to move into the soil from wind and water

How are you able to identify native vegetation

You can look at the depth of the first horizon and also by the colors will tell you what kind of soil it is

Topography affects on soil drainage

Hillsides tend to have great drainage

The surface soil is going to have much more humus and also more organic matter

Catena

A sequence of soils

When all soils in a field have the same period of time, climate, and vegetation, and parent material but differ only in position in landscape