Dru Yates drueyatesgmailcom Learning Objectives List and describe the 5 factors of soil formation List and describe the 4 soil forming processes Be familiar with common soil horizons and corresponding lowercase suffixes used to describe these horizons ID: 415599
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Slide1
A Crash Course in the Genesis and Classification of Soils
Dru
Yates
dru.e.yates@gmail.comSlide2Learning Objectives
List and describe the 5 factors of soil formationList and describe the 4 soil forming processesBe familiar with common soil horizons and corresponding lowercase suffixes used to describe these horizonsList and briefly describe the
10
soil orders in Canada
Identify the
diagnostic soil horizons for each soil orderSlide3Soil Classification: Why?
Why?“…to organize the knowledge of soils so that it can be recalled systematically and communicated, and that relationships may be seen among soil properties and environmental factors, and among soil properties and suitabilities of soils for various uses.”NRC 1998Slide4Soil Classification: How?
How?We classify soils based on dominant soil forming processes.Wait…how do soils form???Slide55 Soil Formation Factors
S = T(C,L,O,P)C = Climate (precipitation, temperature)L = Landscape (aspect, slope)O = Organisms (microbes, plants, insects…humans)P = Parent Materials (unconsolidated material in which soil formation occurs)
T = Time that Parent Materials are subject to Soil FormationSlide6Parent Material
The foundation of the soilTransported or ResidualCan influence:pHtexturefertilityWeathering can be:
Physical
Chemical
Biological Slide74 Soil Forming Processes
AdditionsTransformationsTranslocations
LossesSlide8Describing Soil Processes…
What is being added?What transformations and translocations are taking place in this profile?What is being removed?How have C L O P at this site affected these processes over time? Slide9- Organic matter
– accumulation of OM; leaching of clay (eluviation) – accumulation of clay (illuviation); red-ox – accumulation of carbonates; less weatheredR – unweathered
rockSlide10Describing Horizons
Mineral horizonsA: surface horizon; eluviation and OM accumulationB: “diagnostic horizon”; the next level of soil developmentC: parent material; least amount of soil formation evidentSlide11Describing Horizons
A suffix is needed to describe all but C and R horizonsCommon combinations: A – h, e, p B – h, f, t, n, m, v C – ca
, s,
sa
, gSlide12Describing Horizons
Organic HorizonsLFH: folic (leaf) materials; measured as “above” the soil surfaceLitterFibricHumicO: peat materials; measured as “below” the soil surface
Of
-
fibric
Om
-
mesic
Oh
-
humic
Oco
–
coprogenous
earth derived from aquatic originsSlide13LFH or O?
A? – accumulation of OM; leaching of clay (eluviation)B? – accumulation of clay (illuviation); accumulation of OM and Fe & Al oxidesC? – accumulation of carbonates; cemented horizon R –
unweathered
rockSlide14Slide15Canadian Soil Classification
Taxa
Principles Used
No. of Classes
Order
Dominant soil forming process
10
Great Group
Strength of
soil
forming process
31
Subgroup
Kind and arrangement of horizons
231
Family
Parent material characteristics
~10,000
Series
Detailed features of the pedon
~100,000Slide16The 10 Soil Orders
Regosolic OrderWeak developmentLack B horizonBrunisolic OrderSlightly developed “brown” soilsHave a modified B horizonLuvisolic Order
Well developed “washed” soils
Clays are
eluviated
downwardsSlide17Soil Orders
Gleysolic OrderWell developed “gleyed” soils Fluctuating water tableChernozemic OrderWell developed “grassland” soils
Organic matter accumulation within A horizon
Solonetzic
Order
Well developed “salty grassland” soils
Similar to
Chernozem
, but with salt accumulationsSlide18Soil Orders
Podzolic OrderStrongly developed “forest” soilsOrganic matter and iron/aluminum oxides accumulate in B horizonOrganic OrderMatured organic soilsThick accumulation of decomposing organic matter
Cryosolic
Order
Moderately developed “frozen” soils
Have a permafrost layer
Vertisolic
Order
Well developed “clay” soils
Contain slickensides and
argillopedoturbationSlide19Cheat Sheet
Step
Criteria
Result
1
Does soil have permafrost within 1 m of the surface or within 2 m if strongly
cryoturbated
?
Cryosolic
Order
2
Does the soil have organic horizons (Of, Om, Oh) at least 40 cm thick (60 cm in the case of Of)?
Organic Order
3
Does the soil have both
vertic
and slickenside horizons within 1 m of mineral surface?
Vertisolic
Order
4
Is there a
podzolic
B horizon (Bf,
Bhf
, or
Bh
at least 10 cm thick)?
Podzolic
Order
5
Is there a
Bg
(or Cg within 50 cm of surface) at least 10 cm thick?
Gleysolic
Order
6
Is
solonetzic
B (
Bn
or
Bnt
) horizon present?
Solonetzic
Order
7
Is
chernozemic
A (Ah or
Ap
)
present and >10cm?
Chernozemic
Order
8
Is there a
Bt
horizon at least 5 cm thick?
Luvisolic
Order
9
Is there a
Bm
,
Btj
, Bf, or
Bfj
at least 5 cm thick?
Brunisolic
Order
10
Does this soil not meet any of the criteria above?
Regosolic
OrderSlide20Great Groups
Canadian Classification of Soils…Humo-Ferric Podzol Great GroupThese soils have a Bf horizon thicker than 10 cm (or Bhf + Bf > 10 cm thick), organic C between 0.5 and 5%, and occurs at the drier end of the
Podzolic
range.
Humic
Podzol
Great Group
These soils are found at the wetter end of the range (either by region or landscape position) and have a
Bh
horizon thicker than 10 cm, and organic C > 1%.
Ferro-
Humic
Podzol
Great Group
These soils occupy the intermediate position in the range. The Ferro-
Humic
Podzols
have a
Bhf
horizon thicker than 10 cm and organic C >5%.