tanah dan lingkungan 1 2013

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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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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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Climate

Vegetation

Topography

Parent Material

Time


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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Parent Material

Climate

Vegetation

Topography Time


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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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

tanah dan lingkungan 1 2013

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