Soil Science Quiz 2 (Chapter 4)

Spherodial

Granular structure consists of roughly spheroidal aggregates that may be separated from each other in loosely packed arrangements

Stokes Law

Soil particles are denser than water , they tend to sink, settling at a velocity that is proportional to their size, "The bigger they are, the faster they fall"

Kind, amount

Soils properties such as shrink - swell behaviors, plasticity, water holding capacity, soil strength, and chemical absorption depend on the _____ of clay present as well as the _______

Organic Polymers

Stabilize soil structures

Angle of repose

Steepest angle to which a material can be piled without slumping

Puddled Condition

Tillage operation when wet, crush or smear aggregates, resulting in loss of macroporosity

Biological Process of Aggregation

(1) Burrowing of Soil animals (2) Networks of roots & plants (3) production of organic glues

Physical - Chemical Processes

(1) Floccuation (2) Swelling & Shrinking of clay masses

Role for Glomalin in Soil Aggregate:

(1) Found in higher concentration stable aggregates (2) Detect proteins (3) Increase soil aggregation and create larger pores for better growth of hyphae

Guidlines for managing soil tilth

(1) Minimize tillage (2) time for dry soil (3) mulching (4) compost (5) include sod crops (6) cover crops & green manure crops (7) apply gypsm & synthetic polymers

Three groups of soil textural class:

(1) Sandy Soils (2) Clayey Soils (3) Loamey Soils

Detrimental effects of tillage

(1) Speeds loss of organic matter (2) Naked no protection

Pore Sizes:

(1) macropores (2)mesospores (3) micropores

3 Major factors that influence soil colors:

(1) organic matter content (2) water content (3) Presence and oxidation states iron and manganese oxides in various minerals

5 Fundamental Surface Area Phenomena:

(1)Greater the surface area, the greater the soils capacity for holding water films (2) Greater surface area, the greater the soils capacity to return nutrients and other chemicals (3) Greater the surface area the greater the rate of release of plant nutrients from weather able minerals (4) Greater the surface area, greater propensity to soil particles to stick together in a coherent mass, or discrete aggregates (5) Microbial reactions in soils are greatly affected by specific surface area

The 4 Principals soil ped shapes:

(1)Spherodial (2) Platy (3) Prismlike (4) Blocklike

Boulders

(1m)

Bulk Density

(weight of dry soil)/ (volume of Soil)

Soil Particle Density

(weight of solids)/( Volume of Solids)

Course:

0.2<2.0

Clay:

0.002 < tremendous capacity to absorb water and other substances

Fine Sand:

0.02 < 0.2

Silt:

0.02 < invisible to naked eye, feels smooth, relatively small size with large surface area

Percentages of sand, silt, and clay always add up to?

100%

Gravel

2.0<

Stones or Boulders

250mm or greater: Course Fragments

Clay Loam must contain

26% Clay

Sandy Loam must contain

45% Sand

Silt Loam must contain

50% Silt

Submicroscopic cays

<10^-6m

The "Feel Method"

A moist soil sample is rubbed between the thumb and forefingers and squeezed out to make a "ribbon"

Macropores

Allow ready movement of air and drainage of water allow plant root sand the wide range of tiny animals that inhibit the soil

Blocklike

Blocky pends are irregular, roughly tubelike and range from about 5-50mm across. Modeled by shapes of surrounding blocks

Bearing Strength

Capacity of a soil mass to withstand stresses without rupturing or becoming deformed

Friability

Clods are sticky not hard, cruel easy, revealing their constituent aggregates

Prismlike

Columnar and Prsimatic structures characterized by vertically oriented prisms or pillar like pends that vary in size among different soils and may have a diameter of 150 mm or more

Spatial Arrangement

Complex aggregation, pores, and channels

Microaggregates

Comprised of tiny packets of clay and organic matter only a few micrometers in diameter

Cobbles

Course Fragments ranging from 75 to 250mm

Gravel or Pebbles

Course fragments that range from 2-75mm along greatest diameter

Biospores

Created by roots, earthworms, in tubular shapes

Consistence

Ease with which a soil can be reshaped or ruptured

10,000 times

Fine colloidale clay has about ___________ as much surface area as the same weight medium sand

size

Fine, Medium, Course

Tensile Strength

Force required to pull apart

Subsoiling

Fracture soils to considerable depths, enhancing root penetration

Channers:

Round or Flat fragments

Course Fragments

Greater than 2mm in diameter may effect the behavior of a soil, but they are not considered to be part of the fine earth fraction to which soil texture properly applies

Conservation tillage

Leaves at least 30% of soil surface covered by residues

Moldboard plow

Lift, twist , and inverts soil while incorporating crop

Clay Loams

Loam in which clay is dominant

Sandy Clay Loam

Loam in which sand & clay are dominant

Sandy Loam

Loam in which sand is dominant

Silty Clay Loam

Loam in which silt & clay are dominant

Silt Loam

Loam in which silt is dominant

Floccules

Microscopic Clumps

Loam

Mixture of sand, silt, and clay particles that exhibits the properties of the separates in about equal proportions. Does not that the three separates are present in equal amounts.

Ped

Most commonly used to describe the large scale structure evident when observing soil profiles and involving structural units which range in size from a few mm to about 1 m

Collapsible Soils

Noncohesive materials loosely packed

Sand:

Particles smaller than 2mm but larger than 0.05mm, generally visible to the naked eye and may be rounded or angular

Total Porosity

Percentage of pore space

Tilth

Physical condition of soil in relation to plant growth

Photosynthates

Plant Sugars

Platelike

Platy structures, characterized by relatively thin horizontal sheet like pends (plates) may be found in surface and subsurface horizons. Plates developed as a result of soil forming process

Piping

Process in which silty soils is easily washed away by flowing water

Mycorrhizae

Produce sticky sugar protein called glomalin, which is thought to be an effective cementing agent

Soil Strength

Property of Soil that causes it to resist deformation

Engineer definition of Consistency

Resists penetration

Controlled Traffic System

Restrict all wheel traffic to specific lanes leaving rest of field free from compaction

Peds or Aggregates

Sand, Silt, and Clay, and organic particles become aggregated together due to various forces and at different scales to form distinct structural units

Settlement

Slow, uneven, vertical subsidence

Clay Domains

Small "Stuck" of parallel clay platelets

Condition

Soil amendments to improve management of soil organic matter

Soil Architecture

Soil as an edifice, the primary particles in soil are the building blocks from which the house is constructed. The soil texture describes the sizes of the particles.

Unconfined compression test

Soil column will give suddenly and collapse-when force exceeds the soil strength

Gleyed

Soil exhibiting grass colors from reduced iron and iron depletion

Grade

Strong, Moderate, or Weak

Thixotropy

Sudden liquification of a wet soil mass when subjected to vibrations

Clods

The compressed, cohesive chunks of soil that can form artificially when wet soil is plowed or excavated

Drainage Class

The depth at which gley colors are found

Soil Structure

The manner in which soil particles are aggregated. Defines the nature of the system of pores and channels in a soil.

Soil Texture

The proportion of different sized particles in a soil

Specific Surface Area

The surface area for a given mass of particles

Hyphae

Thin strands of fungi

Ultramicroscopes & Cytophores

Too small to permit the entrance of bacteria

Munsell Chart

Use color chips arranged according to three components of how to see color: the hue, the value, and the chroma

Pemetrometer

Used to measure force needed to push a standard shaped rod into the soil

Microspores

Usually filled with water in feed soils too small to permit much air movement

Loess

Windblown silt deposits

Plow layer

crop residue & animal wastes in a 10-20 mm thick layer of soil

Noncohesive Soils

dry such as loose sand

Gypsum

effective in improving physical condition of soil types

Cohesive Soils

essentially soils with a clay content of more than 15%

Hydrometer

indicates mass of particles remaining in suspension after different settling times

Settling velocity is _________ proportional to viscosity or "thickness" of a fluid

inversely

Stickiness or Plasticity

malleability

Particle Density

mass per unit volume of soil

Interped Pores

occur as spaces between loosely packed granular or as the planar cracks

Soil Scientist definition of consistency

resistance rupture

type

shape