CRSS/ FANR 3060 Exam 1

soil

-layer(s) of generally loose mineral and/or organic material

-affected by physical, chemical, & biological processes

-usually hold liquids, gases and biota and support plants

-non-renewable resource

soil functions

anchorage for plants

storage and recycling of nutrients

regulate water supply

habitat for many organisms

engineering medium

transformations

-weathering of primary minerals to clay & hydrous oxides

-humification of organic matter

-decaying organic matter (biotic) or mineral transformation (abiotic)

additions

from atmosphere & sun, H2O, CO2, N2, organic matter, sediments

losses

leaching out from rainfall (flush out organic matter) or wind erosion

Translocation

move within the profile

clay, organic matter, soils sesquioxides by H2O

nutrient by plants, total soil by animals

unique set of soil properties due to

land

soil

water

rock

dimensions

2D: profile

3D: pedon

Piedmont

Athens is in what physiographic region?

Major Land Resource Areas

• Cross political boundaries

• Represent natural landscape patterns

~50 inches

Average precipitation in GA

Landscape formation

geologic history, underlying rock types, climate (erosion/deposition force)

processes: tectonic (mountain-building), erosional, depositional

uplifting forces

mountain building, continental drift, volcanic activity

leveling forces

gravity, mudslides

humid climate

landscape development: smooth features, gently rolling slopes

arid

angular features, steep slopes

glacial

jagged peaks, U-shaped valley

or

flat prairie pothole

mature landscape

Developed meanders, wide floodplain, rounded divides/edges/low hills, broad flat valley

young landscape

high elevation, steeper slopes

hydrologic cycle equation

P = ET + Q + DeltaS

precp = evapotranspiration + river (discharge) + storage

Energy Balance Equation

Rn=L Et + P + H + G

(all per cm2...)

Rn: net incoming solar radiation (cal/day)

L: heat of vaporization (580 cal/g)

Et: evapotranspiration rate (g/day)

L Et = cal/day due to Et

P: photosynthesis (cal/day)

H: heat re‐radiated back to atmos.

G: heat transferred to soil (later re‐radiated)

2/3 of Rn is LxEt

2% of Rn is P

rest is some combination of H and G

solar energy

Input: 400 cal/cm2/day

dendritic pattern

a stream system that resembles the pattern of a branching tree

developed on relatively uniform bedrock

most common in GA

radical pattern

A system of streams running in all directions away from a central elevated structure, such as a volcano

rectangular pattern

A drainage pattern characterized by numerous right angle bends that develops on jointed or fractured bedrock.

trellis pattern

parallel streams with short tributaries meeting at right angles

develops in areas of weak & resistant bedrock

water budget

Precipitation = evaporation + discharge + storage

weathering steps

rock -> parent material -> soil

Types of weathering

physical, chemical, biological

Physical weathering

expansion/ contraction (Heated/cooled • Ice wedges)

abrasion (wind, water)

Biological weathering

roots wedging, lichens, burrowing animals

Alluvium

water (river, stream); floodplains, terraces; sandy/silty; no B

Colluvium

gravity

footslope (bottom of slope)

similar to upland soils

lacustrine

water transported in dried up lake beds; silty/clayey

aeolian

wind transport in dunes; sandy/ silty

marine

ocean; found in exposed ocean deposits; mixed sands/ clay

glacial till

retreating glaciers; broad glacial plains; mixed sandy/silty

glacial outwash

meltwater from glaciers; areas in glaciated areas; sand/ gravel deposits

Hydrolysis

rxn of minerals w/ H2O or H (low pH = more H)

feldspar (primary) weathering to kaolinite and potassium and hydroxide

pH of rain

5.6 (slightly acidic)

hydration/dehydration

Follows oxidation which would not be very disruptive by itself, but they team up to cause expansion and disruption of mineral structure of rocks

key element in highly weathered soils/rocks of the humid SE

solution

simplest; minerals dissolved in water and may re-precipiate

soluble

halite gypsum

Easily weathered

calcite

biotite (clay & Fe oxides)

slowly weathered

feldspars (clay)

ferromagnesians (clay & Fe oxides)

very slowly weathered

muscovite (clay)

quartz

stable

clay minerals

Fe oxides

soil particle size

fine earth fraction (<2mm)

Sand: 2 - 0.05mm

Silt: 0.05 - 0.002 mm

Clay: < 0.002 mm

How to quantify soil texture?

Texture by feel

• Laboratory- Hydrometer - Pipette- Laser PSA

soil texture

single most important physical property (Soil water dynamics- Soil fertility- Engineering medium)

cannot be changed

tillage

acre-furrow slice: depth of tillage over acre

too much, or when too wet or too dry, breaks down aggregates

soil structure

Soil Structure Is The Arrangement Of Primary Particles into groupings

- Aggregates or peds

Influences Water Movement, gas exchange, porosity, etc.

Describe Using: shape, size, grade

bulk density

ρb is mass of a unit volume of dry soil

ρb = mass oven dry soil/volume of soil

gcm^-3 or Mg m ^-3

measures soil cores & clods

porosity

The amount of pore space in a given volume of soil

Macropores: 0..08 mm Micropores: <0.08 mm

% pore space = (1 - (ρb /ρp)) *100

Diagnostic Horizons

classification determined by the presence or absence of diagnostic horizons and features

epipedons (surface horizons)

all soils have epipdeons except if the soil surface horizon still retains its rock structure or has had no accumulation of organic matter.

Formed at the surface

It has been darkened by organic matter or has been eluviated

Rock structure that may have been present has been destroyed

Folistic Epipedon

more or less freely drained horizon that formed in organic materials

Histic Epipedon A

A saturated horizon that formed in organic materials

Mollic EpipedonA

A thick, dark-colored, humus-rich horizon w/high base status

Ochric Epipedon A

minimally developed surface horizon, typically thin or light colored, that does not meet the criteria for any other epipedon

most common to GA soils

Umbric Epipedon A

A thick, dark-colored, humus-rich horizon with low base status

mollic & umbric epipdeon

thick, dark brown A, high organic matter, different base saturation %

values & chroma less than or equal to 3

folistic & histic epipdeon

• Used with mineral soils with O horizons

• Folistic is freely drained• Histic is periodically saturated

albic horizon

light colored, leached subsoil

Andic Soil Properties

Unique soil properties associated with materials that are rich in volcanic glass or poorly crystalline minerals

Aquic conditions

Saturation in the soil to the extent that it results in the depletion of oxygen; gleyed color

argillic horizon

Subsoil horizon with an illuvial accumulation of clay

calcic horizon

Subsoil horizon with an illuvial accumulation of calcium carbonate (CaCO3)

Cambic horizon (Bw)

Subsoil horizon with minimal development (weak, blocky)

Kandic Horizon

Subsoil horizon with a low nutrient-holding capacity and significantly more clay than the overlying surface layer

Oxic Horizon (Bo)

Subsoil horizon with a low nutrient-holding capacity and significantly more clay than the overlying surface layer; well oxidized

spodic horizon

Subsoil horizon with an illuvial accumulation of organic matter in complex with aluminum and also commonly iron

Argillic, Cambic, Kandic

argillic: results from translocation of clay from above eluvial horizons

kandic: like argillic, but more weathered

cambic: reps structure & color development (early B)

albic & spodic

albic: white leached horizon

spodic: accumulation of in subsurface layers giving a dark brown color

calic & petrocalcic

calcic represents secondary accumulation of CaCO3

nodules, filaments, etc.

petrocalcic: cemented layer of CaCO3

management

Poor physical condition of top soils (tilth) reduces root growth and vigor and seriously reduce plant performance and yield

helps management to

avoice compaction from traffic/tillage

Break up dense layers (deep tillage)

Till only when necessary (preserve aggregates, humus)

Add humus

improve structure on fine‐textured soils

increase water‐holding capacity of sandy soils

Soil Chemistry

nutrient status, contamination, acidity & alkalinity (pH), salt accumulation, sorption & precp, redox

soil colloids

most chemically active part of soil

hums, clay, Fe & Al oxides

permanent charge

isomorphous substitution: subs one cation for "normal" one at time of mineral formation . . . "mistake"

results in extra - charge from O

variable charge

pH dependent

Hydroxl and other functional groups releasing H+

Happens at edges of clay

Common in humus, 1:1 clays, oxides, and amorphous minerals

Montmorillonite

2:1

open interlayer, water and soluble cations

- swelling clay: water goes in/out, shrink/swell

hydrous mica

2:1

partial K removal from interlayer of mica

- initial weathering product of muscovite hydrolysis

vermiculite

2:1

Mg bonded with H2O in interlayer- forms from hydrous mica; some shrink/swell

chlorite

2:1

Al(OH)3 sheet in interlayer ("2:2" clay mineral) - rare in soils; partial Al layer: "chloritized vermiculite"

(most common 2:1 in SE soils ... )

Salt-affected soils

Saline soils - accumulate neutral soluble salts

Sodic soils - lots of Na on exchange sites

Saline‐sodic soils - high EC and high Na