Transcript Lecture 3a Naming Soil Horizons

Lecture 3a
Naming Soil Horizons


Soil horizons (layers
in the soil) are
named so
differences
between soils can
be identified.
Naming soil
horizons takes
practice


When soil
scientists are
describing a
soil they will
discuss a lot
about what
they are seeing
and how it
should be
named.
And what they
are not seeing
and what it
should not be
called ?
Soil Judging


Students wanting more practice at naming soil horizons should
take Soil 4511 and try out for the Soil Judging Team Students
that participate in the “Soil Judging” contest get more practice
with different soils from the region. (MN, SD, ND,MO,IA,KS,NE.
The contest this fall is in Nebraska near North Platte.
Contest in Kansas 2006
2007 UM Soils Team in the Team Pit No. 1 in
southwest Iowa: Left to right Meryl Larson, Erin
Andrews, Nick Reep, and Nick Saumweber
Organic Horizons
O - horizon - organic
material (no mineral
materials)
1) forest litter
2) organic soil or peat
soils, or muck
Oi - undecomposed (fibris)
Oe - moderate decomp.
(hemis)
Oa - decomposed (sapric)




Organic Soil Profile
This trenching
machine is digging
through the Oe
horizon of an
organic soil.
Trenches needed to
remove water so the
peat will dry before
harvest.
Organic Soil Horizons in a forest litter
Oi
Oe
Processes of Mineral Soil Horizon Formation




A. Additions - H2O, organic matter,air, soil
particles, salt
B. Losses - H2O, organic matter, CO2 ,
nutrients by plant removal
C. Transformations - Changes to soil
structure, development of clay minerals,
weathering of minerals to elements, chemical
Rx
D. Translocations - movement from one
horizon to another of O.M. Clay, Water,
Iron, & Nutrients in colloidal size, (very
small particles) clay films on peds are
evidence of this translocation = clay (film)
coating
Mineral Soil Horizons


A horizon - surface
horizons that accumulate
O.M.
Ap = plowed soil
Ap
Ap
EB
Bt
BC
C
E Horizons


E - (formerly A2) Translocation out - Zone
of Eluviations - Leaching
out
lighter in color than
horizons above or below
A
E
E/
B
Bt
BC
C
B Horizons- two kinds:


a) Translocation in below an A, E, or O with
an accumulation of clay,
iron, humus (O.M.
decomposed.)
or carbonates (CaCO3)
zones of illuviation
b) or alteration of the
original parent material,
development of color or
structure - Bw
Bt
C Horizons

C - little affected by
pedogenic processes and
lack properties of O-A-BE- or is the Parent
Material
Solum =
A+B
C horizon
Rock Horizons


R = hard rock
Cr = Soft Rock
Subscripts - all B horizons have a subscript, most transition
horizons do not. * = Important for MN










* a - sapric - organic soils - well decomposed
* b - buried soil horizon
d - dense - geogenic soil material (compacted by glacier)
* e - hemic - mod. decomp. - organic soil
f - frozen soil - permanently frozen, permafrost
* g - gleyed soil - gray color due to low O2 - reduction of
Fe
* h - accumulation of humus - O.M. other than in the A or
O horizons
* i - fibric - organic - non-decomposed
* k - accumulation of calcium carbonate (CaCO3)
* m - cementation - hard - indurated
Subscripts cont.











n - sodium accumulation
* p - plowing - only used with A
q - silica accumulation - very weathered or old soil
* r - soft rock - used with C or Cr
* s - sesquioxides (1.502) (Fe2O3) accumulation of Fe and
Al - red color
*ss – slickensides present –shiny surface on ped face caused
from soil rubbing against soil
* t - clay accumulation - clay films
* w - color or structure development (Bw)
x - Fragipan - hard, dense layer that developed with time
y - gypsum accumulation (CaSO4)
z - salts more soluble than gypsum
(KCL - NaCl - NaSO4)
Transition Horizons





AB - Like A - some of B
BA - Like B - some of A
AE AC BC
E/B - Both E and B particles
are present “B & E” used for soils
with Lamellae
- thin bands of accumulating
clay and iron in sandy soils
Lithologic Discontinuity





A
Bw1
Bw2
2C
L.D. isdesignated by number in front
of horizon = more than one
parent material
2 parent
Loamy Mantle
materials
Outwash
Practice at naming horizons –
Soil from Badlands of North Dakota---Texture of horizons 1,2,3,4 = loam--Note Carbonates in horizon 3

DYAD – Name 4 horizons Using one transition horizon
---

---

---

---
Sandy soil from Northeast Minnesota
Texture of Horizon 1,2,3,4 = Sand
Goodhue County Soil, Southwest of Redwing Mn.
Texture of horizon 1 & 2 = Silt Loam,
Hrz 5 = Silty Clay
Hrz. 4 = Cobbly loam,
Hrz. 5 = Loam





A
E
Bt
2BC
2C