Soils and Fertilizers- Exam 1

5 soil forming factors (CLORPT)

climate, organisms, relief, parent material, time

Rock+weathering=

parent material

Igneous rock (basalt, granite)

basic material of the earths crust, created by cooling and solidification of molten material.

sedimentary rock (sandstone, limestone, shale)

forms when loose material are deposited and slowly cemented or pressurized (75% of earths surface)

metamorphic rock (a change)

formed when igneous or sedimentary rocks are subjected to intense heat and/or pressure

weathering

natural process that breaks down rock into parent material

types of weathering

physical and chemical

physical weathering

reducing of particle size

1. frost wedging

2. root wedging

chemical weathering

changes chemical composition

1. dissolution

2. hydrolysis

3. hydration

4. oxidation reduction

residual soils

stay in place and keep weathering

transported soil

rock move and weather somewhere else

1. gladical drift

2. wind

3. water

glacial drift

glaciers picked up and transported material and deposited them elsewhere

1. till

2. outwash

3. lacustrine

outwash

course materials deposited near the glacier

till

debris dropped into place w/o sorting

lacustrine

particles reached glacial lakes and deposited in lake beds, small particle size

wind

move in dry climates with little cover

1. eolian

2. loess

eolian

sand carried and deposited

loess

wind deposited silt, important in Mississippi and Missouri river valleys, often upper part of the soil

water

1. marine

2. lacustrine

3. alluvial

marine

formed in the ocean and occure when oceans recede, generally sandy(south georgia!)

lacustrine

formed under freshwater and glacial lakes

alluvial

carried by moving freshwater, large particles near riverbed while small particles further away

colluvial

formed by gravity, sliding and rolling

volcanic

ash blown from volcanos and deposited or carried by the wind, lightweight (pacific northwest and Hawaii)

organic

contains greater than 20% organic matter, form in low oxygen conditions as plants die and decay (Florida)

temperature+precipitation=

climate

temperature

determines rate of chemical reactions
^temp=^weathering

precipitation

movement of soil and chemical reactions
^precipitation=^weathering

organisms

1. vegetation

2. macro/micro organisms

slope and aspect

relief

time

an inch of soil can take 1000 years to form but a second to disturb. soil becomes les like parent material over time

soil forming processes

1. Additions

2. Translocations

3. Transformations

4. Losses

soil profile

vertical cross section of a soil

soil horizon

horizontal layer of soil created by soil forming processes differs in physical and chemical properties

6 master horizons

top to bottom

1. o

2. a

3. e

4. b

5. c

6. r

O horizon

organic matter, cultivated, dark color, found in undisturbed layers

A horizon

topsoil, most productive

E horizon

zone of eluviation, rare, bleached white color

B horizon

subsoil, zone of accumulation

C horizon

substratum, most like parent material

R horizon

hard bedrock

soil taxonomy

a hierarchical system to classify soils based on similar characteristics

1. order

2. suborder

3. great group

4. subgroup

5. family

6. series(common name)

subdivisions(subhorizons)

lowercase letters following master (Ap)

vertical subdivisions

numbering after horizon

order

12, broadest group

suborder

based on annual moisture and temperature

greatgroup

adding a prefix to the suborder name

subgroup

adjective describing the rest, (ex. Typic)

family

most descritive catagory

series

common name

Alfisols (13%)

"alf" temperate deciduous forest, acidic surface horizons

Andisols (2%)

"and" pacific nw, alaska and hawaii, volcanic

Aridisols (12%)

"id" cool or hot deserts, mostly in the western US

Entisols (8%)

"ent" lack well-developed horizons, youngest order

Gelisols

"el" tundra, cold desert, or high peaks, fragile, alaska

Histosols (

"lst" florida wetlands, carbon sink, from decaying organic matter in wetlands

Inceptisols (16%)

"ept" teenage soils, scattered,

Mollisols (25%)

"oll" best ag soils, midwest

oxisols (

"ox" extremely low organic matter, infertile, puerto rico

Spodosols (5%)

"od" forests in cool, wet regions, FeAl compounds in subsoil, pine forests

Ultisols (13%)

"ult" most commonin the southeast US, highly weathered of warm humid climates

Vertisols (1%)

"ert" prominent crack throughout profile, good ag soils, poor engineering

Dominant southeast soil order

1. ultisol

2. spodosol

3. histosol

4. entisol

5. oxisol

6. alfisol

Land Capability Classes

USDA system that rates land according to suitability for ag and other uses. (8 classes)

Class I

land capability class that has few limitations for use, well drained, and best ag soils

Class II

land capability class that has mild limitations like gentle slope, moderate erosion rish and slightly poor drainage

Class III

land capability class that utilizes the same crops as class I/II with serious problems like steep slopes, high erosion risk, poor drainage, low fertility, and unstable structure

Class IV

land capability class marginal for cultivated crops, same problems as class III, pasture and hay crops are best

Class V

land capability class unsuitable for cultivation, used for pasture, range, woodlands, recreations. flooding risk and short growing season

Class VI

land capability class that has the same problems as class V. steep slopes, severe erosion/risk, stoniness, shallow, drought

Class VII

land capability class that has the same issues but more severe and difficult to maintain pasture.

Class VIII

land capability class that has no commercial production. ex. sandy beachs, rock outcroppings, flooded river bottoms

Land Capability Subclasses

Lowercase letter added to class number

"E" subclass

erosion and runoff

"C" subclass

climatic hazard

"S" subclass

root zone tillage

"W" subclass

wetness

aggregates

secondary unit composed of many soil particles held together by organic substance, iron oxides, carbonate, clays and/or silica

structure promotes

1. fertility

2. stability

3. permeability

4. nutrient holding

5. root growth

structure is not ______________

permanent

how do we classify structure

1. grade

2. class

3. type

factors that affect structure formation

1. pressure

2. microorganisms

3. root activity

4. organic matter

5. nutrients

soil structure class range

very close to very fine

soil structure grades

determined by the stability and strength of peds

1. structureless

2. structured

structured soil grade

1. weak

2. moderate

3. strong

structureless soil grade

1. single grained

2. massive

Soil structure types

1. granular

2. blocky

3. prismatic

4. platy

granular soil structure type

spherical, rapid water movement

blocky soil structure type

cube-shaped

1. angular

2. subangular

Prismatic soil structure type

very large peds

1. columnar

2. prismatic

platy soil structure type

large thin plate-like peds

tilth

physical condition of a tilled soil

soil pans

any layer of hardened soil

1. claypan

2. fragipan

3. duripan

4. plowpan

soil temperature

influences germination and microbial activity

soil color

indicator of soil behavior

munsell color system

standardized way to describe color

sources of elements in soil

1. soil minerals

2. organic matter

3. adsorbed nutrients

4. dissolved iions

colloid

organic and inorganic matter with small particle size and large surface area

why are colloids important?

1. high surface area

2. charge attracts ions

3. adsorb and exchange nutrients

how do colloids get their charge?

1. broken hydroxyl groups

2. isomorphic substitution