Friday, 17 October 2014
Tabel
. Some important Minerals in Soils
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Name
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Formula
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Comments
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Primary
Minerals
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Quartz
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SiO2
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Hard,
weathers slowly, major material of most sands
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Feldspar
:
-
Orthoclase
-
Plagioclase
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(K,
Na)AlSi3O8
(Ca,
Na)Al(Al, Si)Si2O8
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Hard,
weather slowly or moderately, but provide important nutrients and clay in the
weathered products.
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Micas
:
-
Muscovite
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Biotite
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KAl3Si3O10(OH)2
KAl(Mg,
Fe)4Si3O10(OH)2
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“Glitter”
in rocks or wet sands. Important source of potassium and clay
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Dark Mineral (Augite, hornblende,
Biotite, Mica, Others)
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Ca2(Al,Fe)4(Mg,Fe)4Si6O24
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Includes
several minerals that weather moderately fast; good clay formers
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Apatite
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3Ca3(PO4)2.CaF2
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The
most common mineral supplying phosphorus
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Calcite, Dolomite, Gypsum
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See secondary minerals
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Can
be either primary or secondary
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Secondary Minerals
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Calcite
Dolomite
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CaCO3
(Ca,Mg)(CO3)2
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Slightly
soluble materials in limestone or dolomite rock common in arid-region soils;
calcium or magnesium source
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Gypsum
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CaSO4.2H2O
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A
soft, moderately soluble mineral found in arid-region soils
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Iron
Oxides
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Fe2O3.xH2O
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A
group of minerals with different amounts of water giving soils their
yellow-to-red colors; iron source
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Quartz
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SiO2
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Reprecipitated
forms such as opal, agate, and petrified wood
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Clay :
Kaolinite, Illite, Montmorillonite, Vermicullite,
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(Complex)
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Tabel
1. Stage pelapukan mineral
pada fraksi tanah < 2 mm
Stage
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Tipe mineral
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Karakter Tanah
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Stage Awal
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1
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Gipsum
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Mineral ini terdapat di fraksi
debu dan clay pada tanah muda dan tanah di daerah arid dimana air kurang shg
menghambat pelapukan kimia dan pencucian (leaching)
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2
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Kalsit
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3
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Hornblende
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4
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Biotit
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5
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Albit
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Stage intermediate
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6
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Kuarsa
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Tanah banyak ditemukan didaerah
temperate; umumnya subur, rumput atau hutan sbg vegetasi alaminya
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7
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Muskovit
(termasuk ilit)
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8
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Vermikulit
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9
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Montmorillonit
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Stage
lanjut (advanced stage)
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10
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Kaolinit
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Fraksi
clay pada tanah yang terlapukkan lanjut di daerah tropik, kesuburan rendah
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11
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Gibsit
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12
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Hematit
(juga gutit)
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13
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Anatase
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Table. Letter Horizons Most Commonly Encountered in
Soils
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New
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Old
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Description
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Usually Surface Horizons
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Oi,
Oe
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O1
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Organic
horizon in which most
leaves, stems, fruits, and other plant
parts are still identifiable
(includes recent litter). Usually quite thin-a centimeter or so thick
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Oa,
Oe
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O2
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Organic
horizon so extensively
altered that identification of the
parts of plant materials is not usually
possible. Can be many centimeters
thick.
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A
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A1
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Mineral
horizon darkened by organic matter accumulation. Under Oa horizons, it is usually thin; in cultivated soil it is the
surface horizon and may be labeled Ap.
An Ap horizon may be a mixture of
several thin horizons, even including part of a shallow B.
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Usually
Subsurface Horizons
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E
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A2
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A Mineral horizon lighter colored than an A or Oa above it or B below it. Fine clay and minute
organic substances have been washed
(eluviated, leached) out of it by
percolating waters. Usually common in high-rainfall areas, especially under
forests
|
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AB
or EB
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A3
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A transition horizon more like the A or E above it than like the B
below it
|
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BA
or BE
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B1
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A transition horizon more like the B below it than like the A or E above it
|
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B or Bw
|
B2
|
Layer
of illuvial colloids (accumulation) or evidence of weathering below the A horizon (s). Small particles that
have washed from the O, A, or E horizons
have accumulated because of filtration (lodging) or lack of enough water to
move them deeper. Early B horizon
development stages of soils may have only redder (orange, yellow, brown)
colors of weathering caused by the colored iron hydrous oxides. Often higher
in clay than the A. always higher in clay than the E; the top of the B may start at a depth ranging from
about 15-50 cm below the soil surface
|
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BC
or CB
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B3
|
A transition horizon from B to C horizons
|
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C
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C
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Unconsolidated
material (unless
consolidated during soil development
by carbonates, silica, gypsum, or other material) below A or B horizons.
Little evidence of profile development.
|
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R
|
R
|
Underlying consolidated (hard) rock. Cr for softer material.
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Horizon subscripts
Subscripts are added to letter horizons for further
detail, always as lowercase letters. For
example :
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New
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Old
|
Descripton
|
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k
|
ca
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A depositional accumulation of
calcium and magnesium carbonates
(lime)
|
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g
|
g
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Strong
gleying, which is a
result of long-time poor aeration, usually because of excess water. Soil
colors are grays to pastel blues and greens. Ex : Cg
|
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h
|
h
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Deposited
(illuvial) humus from
percolating water (Bh)
|
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t
|
t
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Deposit
(illuvial) clay from horizons above, usually
labeled as Bt
|
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x
|
x
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Fragipan
(hard, silty texture,
brittle hardpan)
|
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m
|
m
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Strong
cementation into hardpan (as
by carbonates,silica)
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Table. Brief
characterizations of the 11 Soil Orders
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Soil
Order
|
General
Features
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Entisol
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Entisols have no profile development
except perhaps a shallow marginal A. Many
recent river floodplains, volcanic ash deposits, unconsolidated deposits with
horizons eroded away, and sands are Entisols
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Inceptisols
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These soils, especially in humid
regions, have weak to moderate horizon development. Horizon development has
been retarded because of cold climates, waterlogged soils, or lack of time
for stronger development.
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Andisols
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A tentative soil order.
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