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Tanah dan Lingkungan
Dr.rer.nat. Junun Sartohadi, M.Sc.
[email protected] in Soil Geography, 2009 ,FGE-UGM
Professor in Natural Resources Management, 2011, ITT-FH Koeln
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UNDERSTANDING THE SOILFORMING FACTORS
S = f (C, O,
P, R, T,
)
Concept from Hans Jenny, 1941
S = f (C, O, H, P, R, T,)Concept from Sartohadi at al, 2012
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All of those factors are interacting to each other in a complex way
Scientist always try to simplify that complex interactions
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Some concept of soil distributions
Climosequencesoil distribution is controlledby climate
Biosequencesoil distribution is controlled by
biota Lithosequencesoil distribution is controlled
by parent materials
Toposequencesoil distribution is controlled
by relief Chronosequencesoil distribution is
controlled by time of formation
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Soil forming Factors
Climate
Biota
Parent Material
Topography
Time
Soils vary from place to place because theintensity of the factors is different atdifferent locations.
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Soil Forming Factor - Climate
Temperature- Warmer = FasterCooler = Slower --> Soil
Development
Precipitation- higher rainfall = greaterleaching
Leaching Zone- determined by location of CaCO3in the soil profile
Leaching Index= Pcpt. - Evapotranspiration= theamount of effective rainfall that can cause soilleaching
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Temperature & Precipitation vs. Clay, Depth to Carbonates & OM
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Leaching
LI = 8 LI = 4 LI = 2
CaCo3 Zone
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Soil Forming Factors
Climate
Vegetation/Biotic
Parent Material Topography
Time
Soils vary from place to place becausethe intensity of the factors is differentat different locations.
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Soil Forming Factors - Biotic (Vegetation)
Animal - Soil Mixing~earthworms, crawfish,scorpions, gophers ~this mixing can result inthe destruction ofhorizons.
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Botic (cont.)
Vegetation - Additon ofOrganic Matter (OM).
Prairie ~ OM added toupper 2 ft. of soil due
to fibrous root systemof grass plants.
Ap
A
AB
Bg
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Biotic (cont.)
Forest ~ OM added to upper 4 due to yearlyleaf fall to surface of soil.
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Prairie - Border Biotic Factor
Prairie - Border soils (oak savannahs) have theinfluence of the prairie and forest ~ due to changesin vegetation over the past 8000 years the soils havebeen both under prairie and forest.
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Biotic
Forest ~ OM added to upper 4 due to yearly leaffall to surface of soil.
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Factors that Slow Soil Formation
Biota and human aswell Mixing by animals or
man
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Soil Forming Factors
Climate
Biota
Parent Materials
Topography
Time
Soils vary from place to place because the
intensity of the factors is different atdifferent locations as well as the localfactors.
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Soil Parent Materials
Residual - Soil formed from Bedrock. In Minnesota only the followingare close enough to the surface to have a soil formed from them:
Sandstone
Limestone Basalt
Granite
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Transported Parent Materials
Water - Rivers = Alluvium
Wind - eolian = sand or silt (loess)
Gravity = colluvium
Ice = Glacial Drift - all materialstransported by ice or as a result of glacialactivity
alluvium
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Transported ParentMaterials
WaterOutwash - often stratified sand or sand and
gravelLacustrine - lake deposited - silt or clay in
texture - fine sediments - flat terrain, former lake
bottom
Beach Ridge
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Wind Loess - wind blown silt (.05 - .002mm
diameter) Sand - dune sand - wind blown sand
(eolian sand)
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Soil Forming Factors
Climate
Vegetation
Topography
Parent Material
Time
Soils vary from place to place because the
intensity of the factors is different atdifferent locations.
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Among those
soil forming
factors, relief
and vegetation
are directlydepicted in the
remote sensing
images
For the mapping purposes, the scientist try to explore the
relationships between external soil characteristics and
internal soil characteristics
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Topography or Landscape Position
Catena - A series of soilswith different horizonsdue to differences intheir depth to the water
table Drainage classes
Well-drained
Moderately well-drained
Somewhat poorly drained Poorly drained
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Topography erosion & deposition
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Summit and Backslope
Summit will have minimumerosion and maximum soildevelopment (greatest horizonation).
Backslope will be similar tosummit unless slope is >20%.
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Shoulder
Greatest erosion - least water infiltration -greatest runoff - minimal soil development.
Ap
Bw
Bk
BC
C
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Footslope Deposition of materials from upslope - may be
near water table - may have greatest leachingdue to water from upslope and rainfall.
Ap
A1
A2
A3
AB
Btg
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Slope Aspect
Direction the slope faces
Important when slope > 10 %
A
Bw
C
A
Bt
C
E
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Soil Forming Factors
Parent Material
Climate
Vegetation
Topography Time
Soils vary from place to place because the
intensity of the factors is different atdifferent locations.
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Soil Forming Factor - Time
Vegetation and Climate act on the ParentMaterial and Topography over Time.
The age of a soil is determined by its
development and not the actual number ofyears it has been developing.
How long it takes for a soil to become olddepends on the intensity of the soil formingprocesses or intensity of the other 4 soilforming factors.
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Age Sequence
Youth = Juvenile =A
CA
Bw
C
Mature =A
E
Bt
C
AdultA
E
Bt1
Bt2
Old AgeSenile
A
E
Btqm
Bqm
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Factors that retard soil profile development
low rainfall
high lime content
high clay content
steep slopes cold temperature
severe erosion
low humidity
high quartz
hard rock
high water table constant deposition
mixing by animals
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What happens to a soil with time
Loss of nutrients ( bases) = lower pH orsoil becomes more acid
Increase in concentration of iron or soilbecomes redder
Increase in clay content or old soilshave more clay
Deeper weathering into the parentmaterial
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Deep Weathering
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Soil Layer Soil Horizon
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Soil Horizon
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Soil Horizon
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Soil Layer
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Soil Horizon
Layer
Horizon
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Type of rock weathering a process of soil parent materialsformation
Sphereoidal
Weathering
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Type of rock weathering a process of soil parent materialsformation
Concoidal
Weathering
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Parent rock weathered soil parent materials
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Formation of soil parent materials influenced by rock structure
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Formation of soil parent materials influenced by rockstructure
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Formation of soil parent materials influenced by rockstructure
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Batuan Induk Bahan Induk
Bahan induk ada 2 :
1.) Residual B.I. yang berasal dari batuandibawahnya
2.) Transported B.I. yg bukan berasal daribatuan dibawahnya
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Bagaimana sebenarnya bentuk tanah di
lapangan ?
Tanah merupakan tubuh alam 3 dimensi, yg memiliki arahpenyebaran ke vertikal dan ke arah horisontal.
Ke arah vertikal dari permukaanlapisan batuaninduk
Ke arah horisontal horison tanah
Susunan lapisan tanah yang terdiri dari horison-horison tanahdisebut profil tanah
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Gbr. Profil Tanah
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Bagaimanakah tanah terbentuk ?
Syarat utama terbentuknya tanah :
1. Tersedia bahan asal (bahan induk)
2. Adanya faktorfaktor yg mempengaruhi bahan asal tersebut
Lapisan-lapisan tanah (horison tanah) terbentuk akibat prosesPedogenesis
Proses Pedogenesis proses pembentukan tanah karena adanyatransfer materi & energi di dalam profil tanah.
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Bagaimana mekanismenya ?
Batuan Induk (lapuk) Bahan Induk Tanah
Weathering process
Proses pedogenesis
Physical weathering
(temperature, water, wind, glacier)
Chemical weathering
(oxidation, carbonation, hydration, solution)
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Perkembangan tanah pd kondisi ideal
Kondisi ideal :
1. Iklim tropik basah
2. Tidak tergenang/berdrainase baik
3. Tidak tertimbun material baru
4. Tidak terkikis secara dramatis
(ex : erosi, longsor)
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Proses Pedogenesis
Horison C = horison bahaninduk tanah
tanah regolith
1 2
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A = horison dengan ciri berbutir
halus, horison permukaan berwarna
gelap kaya akan organik
2 3
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B = horison dengan batuan yg masih utuh
3 4
Iklim
- Pohon yg mati
membusuk
pembusukan
sempurna- Lebatnya
vegetasi
membuka pori2
tanah
- akibatnya
material yg
diatas terangkutkebawah
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Dari kondisi 4. tanah selanjutnyaberkembang menjadi tanah tua,dgn horison O, A, E, B, C, R.
- Horison O berada padabagian lapisan atas tanah,mengandung humus pd vegetasilebat.
- Horison E warna pucatmendekati putih sbg. Akibatterjadi penyelindihan olehmaterial diatasnya, mengandungsilika dan alumina
- Horison C dan R
bukanTanah, tapi Induk Tanah
- Horison O, A, E, B Tanah,merupakan solum (=
kedalaman Tanah)
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Berbagai perkembangan Tanah
Kondisi Tidak Ideal1) Kondisi tergenang/drainase buruk
- Biasa berada pd daerah cekungan
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perkembangan lebih lanjut
pH tanah menjadi super masam sebagai akibat dari proses drainasetanah-tanah yang tergenang:
Fe + SO4 FeSO4
Berwarna merah kekuning-kuningan Cat clay
Selanjutnya bila FeSO4 terurai menjadi Fe3+ dan SO4, maka akan
membentuk FeOH dan H2SO4 Bila H2SO4 bereaksi dgn Al
2+, maka dapat membentuk bongkah2
tanah yang sulit terurai dalam airkoagulasi
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2) Kondisi Kering
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3) Kondisi kering & basah
Pd. Saat kemarau, maka air dlm tanah naik (menguap) membawaNa, Ca, Mg, K membentukstruktur gumpal kejenuhanbasa > 50 %
Pd. Saat musim hujan, air turun/masuk ke dalam tanahmembawa Na, Ca, Mg, K membentukstruktur tiangkejenuhan basa < 50 %
Kondisi ini terjadi pada horison B
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KONDISI YG SPESIFIK
1) Bahan Induk Abu G.Api
Letusan eksplosive tipe strato
Iklim tropik humid pelapukan cepat clay(lempung) amorf
Selanjutnya membentuk alloplaneimogolith dgnBJ rendah, konsistensi smeary = gembur spesifik
warna hitam kelam dgn value kroma 2
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2) Bahan induk batuan Gampingan (calcareous rock)
Kaya akan Ca2+
& membentuk suasana basadgn pH tinggi
Pd iklim hangat, membentukSmectite clay
lempung yg mempunyai sifat kembang kerut tinggi
Smeetite clay, dpt pula terbentuk pd. Daerah vulkanik,terutama pd batuan luar yg mengandung Ca - Plagioclas
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Soil Forming Factors
Parent Material Climate
Vegetation
Topography Time
Human
They modify the natural process: accelerate,decelerate, alternate but not stop it
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Acceleration of soil erosion creates shallowand/or direct contact soil to bed rock and/orremove top soil layers
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Intensive cultivation with irrigation wateraccelerates clay pan formation that deceleratewater percolation
Clay pan
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Terracing has triggered landslide. It restarts thesoil formation