Soil Science SimplifiedPpt 1 - IntroMENGAPA

KITA MEMPELAJARI

TANAH ?FOTO: smno.kampus.ub.janu2013

Mengapa kita mempelajari TANAH ?

TANAH sangat penting:– Media untuk produksi tanaman– Pembersih air dan limbah– Produsen dan penyerap gas-gas– Rumah bagi berbagai organisme– Medium untuk pertumbuhan tanaman– Dekomposer limbah– Sumber bahan untuk konstruksi , seni dan obat-obatan, dll.– Dokumen sejarah manusia, geologis, klimatis, dan biologis– Sumberdaya alam esensial.– Tempat mendirikan bangunan, dan lainnya.

HUBUNGAN TANAH DAN TANAMAN

Diunduh dari: ……….. http://cnx.org/content/m41620/latest/

Soil-Plant Nutrient Cycle.

Figure illustrates the uptake of nutrients by plants in the

forest" soil ecosystem.

Source: U.S. Geological Survey.

HUBUNGAN TANAH DAN TANAMAN

Diunduh dari: ……….. http://phasm.co.uk/guerrilla-soil-science/soil-properties/

Plants as primary producers require mineral elements which they remove from the soil and combine with Carbon Dioxide

(CO2) (from the Atmosphere) and Water (H2O) (also taken from the

soil matrix) to produce the sugars, carbohydrates and

proteins, required for growth.

Tanaman mendapatkan air dan hara dari dalam tanah,

penyerapannya melalui bulu akar.

HUBUNGAN TANAH DAN TANAMAN

Diunduh dari: ……….. http://preuniversity.grkraj.org/html/4_PLANT_AND_WATER_RELATIONSHIP.htm

Most of the water is absorbed by the plants is through root hair zone. 

The figure shows the pathway of soil water into

root system.

HUBUNGAN TANAH DAN TANAMAN

Diunduh dari: ……….. http://festuca.weebly.com/

Figure : (a) shallow soil

without a B horizon has low water storage and can restrict root growth and

(b) deeper soil with all three horizons with no physical constraints to root growth

(Reference:senrm.sa.gov.au).

KUALITAS TANAH

Sifat Fisika

Kesuburan Tanah

Aktivitas Biologis

“The ability of soil to function; to supply plants with adequate essential nutrients,

have good drainage and aeration, promote root growth and soil biological activities.”

Konteks: Tipe Tanah, Slope, Iklim…….

Problem

- Salinitas

- Miskin Hara

- Erosi tanah

- Drainage

Tanah …OK

Kualitas Tanah

- Kaya BOT

- Sifat Olah

- Infiltrasi Air

- Ketersediaan Hara

KUALITAS TANAH

air25%

water25%

minerals (sand, silt, clay)45%

BOT 5%

EMPAT KOMPONEN TANAH

SIFAT DAN FUNGSI TANAH

1. Tanah = Soil – selimut tipis di permukaan bumi, terdiri atas bahan mineral dan bahan organik, air dan udara dan mampu mendukung pertumbuhan tanaman.

2. Fotosintesis – plant ability to combine CO2 and H2O from the ground into sugar (C6H12O6). Light furnishes the energy for this reaction. Nitrogen, sulfur and phosphorus are required for synthesis of plant proteins too.

1. Sebagai medium tumbuh tanaman, tanah memainkan empat fungsi:1. Jangkar akar tanaman2. Suplai air3. Menyediakan udara4. Menyediakan unsur hara tanaman

2. Ruang pori di antara padatan tanah diisi oleh air dan udara.

3. Air takes up part of the pore space not occupied by water. As the water increases, the air content decreases. In respiration (opposite of photosynthesis), plant roots use oxygen and give off carbon dioxide. So, soil usually contains less oxygen and more carbon dioxide than atmospheric air does.

4. Millions of microbes live in each ounce of fertile soil. Without them, soils would become inactive and lose their ability to support plants.

SIFAT DAN FUNGSI TANAH

TANAH SBG MEDIA TUMBUH TANAMAN

• Soils and growing media are made up of two types of materials:– Bahan organik Tanah (BOT)– Bahan / senyawa anorganik

PROFIL TANAH

PROFIL TANAH

• Lapisan-lapisan dalam profil tanah disebut “horizon”

• Profil tanah yang khas:– Horizon A atau Topsoil

• most fertile• most organic matter• top or first layer

– Horizon B atau Subsoil– Horizon C atau Batuan induk

PROFIL TANAH

Typical layers found in a soil profile. (Source: PhysicalGeography.net)

Sumber: http://www.eoearth.org/article/Soil

Most soils have a distinct profile or sequence of horizontal layers. Generally, these horizons result from the processes of chemical weathering, eluviation, illuviation, and organic decomposition. Up to five layers can be present in a typical soil: O, A, B, C, and R horizons.

The O horizon is the topmost layer of most soils. It is composed mainly of plant litter at various levels of decomposition and humus.

A horizon is found below the O layer. This layer is composed primarily of mineral particles and has two characteristics: it is the layer in which humus and other organic materials are mixed with mineral particles, and it is a zone of translocation from which eluviation has removed finer particles and soluble substances, both of which may be deposited at a lower layer. Thus the A horizon is dark in color and usually light in texture and porous. The A horizon is commonly differentiated into a darker upper horizon or organic accumulation, and a lower horizon showing loss of material by eluviation.

The B horizon is a mineral soil layer which is strongly influenced by illuviation. Consequently, this layer receives material eluviated from the A horizon. The B horizon also has a higher bulk density than the A horizon due to its enrichment of clay particles. The B horizon may be colored by oxides of iron and aluminum or by calcium carbonate illuviated from the A horizon.

The C horizon is composed of weathered parent material. The texture of this material can be quite variable with particles ranging in size from clay to boulders. The C horizon has also not been significantly influenced by the pedogenic processes, translocation, and/or organic modification.

PROFIL TANAH

Soil Profile: a vertical section of soil from the ground surface to the parent rock

Soil Profile :

Soil typically consists of layers of material, called horizons, which differ in both texture

and appearance.

A soil profile is a cross section of these layers, and it measures the different

characteristics of each layer.

Sumber: http://topics.wisegeek.com/topics.htm?soil-profile#

PROFIL TANAHSumber: http://

saburchill.com/lab/field/field02.html

There are four distinct layers of soil under the leaf litter.

1. Leaf Litter (Layer A)2. Humus (Layer B)3. Humus with some minerals 

(Layer C)4. Minerals with very little

humus (Layer D)

PROFIL TANAHSoil profile and names of horizons

Hypothetical soil profiles with example of codes for horizons. L (or F): Litter (Förna = litter)0: Litter layer of not or little decomposed plant material

A: Eluviation layer, divided into:   A1: Upper layer, dark in color, very rich in humus   A2: Mineral layer relatively poor in clay material, iron, aluminium or all three due to leaching

B: Illuviation horizon, divided into:   B1: Gradual transition layer from A2 to B2   B2: Layer with maximal illuviation   B3: Gradual transition from B2 to a C-horizon.

C: Unconsolidated earth material. Not or only little weathered materialg: g indicates the layers where iron, sedimented under anaerobe conditions, became oxidized later to ironoxide or rost

G: G indicates the permanent non-aerate or poorly aerate parts of the soil, characterized by the blue-gray color of ironsulfide (FeS = pyrite). These layers are mostly in the deeper part of the profile.

Sumber: http://www.vcbio.science.ru.nl/en/virtuallessons/landscape/soil/

PROFIL TANAH

Diunduh dari sumber: http://www.as.wvu.edu/~rbrundage/lecture7b/sld004.htm

FISIKA TANAH

• Soils consist of solid, liquid, gaseous and biotic components.

• Sand and silt are merely broken down rock frags (consists of quartz, feldspar, mica, or other minerals). Chemically they are essentially inert compared with clay and organic matter, which are responsible for most of the chemical reactions in the soil.

Soil fraction

Diameter Description

Gravel Larger than 2 mm

Coarse

Sand 0.05 - 2 mm

Gritty

Silt 0.002 – 0.05 mm

Floury

Clay Smaller than 0.002 mm

Sticky when wet

SIFAT FISIKA TANAH

LIAT = CLAY

1. Clay particles are plastic and sticky when wet. They are highly adsorptive of water, gas, and dissolved substances.

2. Liat berukuran halus, bentuk pipih; kristal aluminosilicate terdiri atas Si, Al, Fe, Mg, O, dan H.

3. Ada beberapa tipe liat, dua tipe liat yang sangat penting adalah kaolinite dan smectite. Smectite clays have the ability to swell on wetting and shrink when dry.

1. Liat adalah koloid yang bermuatan negatif. This negative charge is the reason that positively charged cations surround each clay particle. The individual cations can be exchanged for each other.

2. Kalau kation dapat mendekati permukaan liat, muatan negatif pada permukaan liat akan dinetralisir dan partikel-partikel liat akan saling berikatan dengan jembatan kation atau liat mengalami flokulasi.

3. Ca dan Mg menjadi jembatan pengikat partikel-partikel liat menjadi flokul. Kedua kation ini ukurannya cukup kecil dan efektif mengikat bersama partikel-partikel liat.

LIAT = CLAY

• TEKSTUR TANAH – PROPORSI RELATIF berbagai ukuran partikel (separat) dalam tanah.

• Nama-nama kelas tekstur tanah, mis. Pasir-berlempung (Loamy sand), Lempung-debu (Silt loam), Lempung-liat (Clay loam) dan Liat-berdebu (silty clay).

• The best soils are generally those which contain 10 to 20% clay, with silt and sand in approximately equal amounts, and a fair amount of organic matter.

TEKSTUR TANAH

The content of sand, silt, and clay for the twelve

main soil texture classes can be found on this

triangle.

Misalnya tekstur Lempung berpasir

(Sandy loam ) mengandung 65% pasir,

25% debu (silt), dan 10% liat (clay).

SEGITIGA TEKSTUR TANAH

• In comparing clay with sand and silt, it is important to be aware of the relative amount of surface area of these particle size groups, bc it is on the surface that many chemical and physical processes take place.

• Partikel yang ukurannya lebih kecil = luas permukaannya lebih besar (misalnya Liat)

LUAS PERMUKAAN

Sumber referensi: ………

Partikel Tanah Diameter Partikel

Partikel dalam 1 gram

Luas permukaan dari

1 gram

PASIR = Sand 2 mm 90 11 cm2

DEBU = Silt 0.02 mm 90,000,000(9x107)

1130 cm2

LIAT = Clay 0.0002 mm 9x1013 113,000 cm2

PARTIKEL PRIMER TANAH

• STRUCTUR TANAH – tatanan individual partikel-partikel dalam hubungan satu sama lain. Struktur tanah merupakan tatanan partikel-partikel menjadi “kelompok kecil” atau disebut agregat tanah.

• Agregat-agregat kecil dapat berikatan satu sama lain menjadi agregat yang lebih besar , disebut Gumpalan (ped).

• Gumpalan (bongkahan, Ped) bentuknya bermacam-macam , membulat, balok , kolom, pipih.

• If the individual particles are arranged in small aggregates with rounded edges, we speak granular structure. This is very desirable for plant growth bc it provides both large and small pores.

• Bebertapa tanah strukturnya tidak ada. Sandy soils the individual grains act independently of each other. No binding substances hold the particles together, so the soil has no peds.

STRUKTUR TANAH

• Bagaimana partikel-partikel tanah berkelompok:– Butiran tunggal– Granular (best for most plants)– Balok - blocky– Pipih - platy– Masif - massive

STRUKTUR TANAH

Single Grain

STRUKTUR TANAH

Remah - Granular

STRUKTUR TANAH

Gumpal - Blocky

Pipih - Platy

STRUKTUR TANAH

Massive

• Struktur tanah sangat penting bagi petani yang menanam tanaman pada kondisi tanah alamiah

• Producers of container grown plants add ingredients to make growing media desirable

STRUKTUR TANAH

• Ukuran partikel• Tipe tekstur

– Berliat– Berlempung– Berpasir

TEKSTUR TANAH

TEKSTUR BERLIAT1. Partikel-partikel halus2. Mempunyai kemampuan

besar untuk menahan/menyimpan air

• Kelas tekatur lempung mempunyai pasir, bedu dan liat hampir sama

• Tekstur ini sangat ideal bagi pertumbuhan tanaman secara umum

TEKSTUR BERLEMPUNG

• Partikel ukuran besar• Kemampuan

menyimpan air sangat rendah

TEKSTUR BERPASIR

1. Pori ukuran besar mudah merembeskan air dan diisi udara setelah hujan lebat. Pori ini sangat penting bagi sistem aerasi tanah.

2. Pori ukuran kecil (pori mikro) menahan air melawan gaya gravitasi dan dapat mendorong air ke arah atas dari muka-air dengan cara kapilaritas.. Pori ini penting dalam suplai air bagi tanaman.

3. Ideal structure includes large and small pores in proportions that corresponds to the water/air needs of the crop plants given for that culture or climate.

PORI TANAH

1. Just as important to plant growth as air temp. The temp of the surface soil fluctuates greatly both during a 24 hr period and with the seasons.

2. Kalau permukaan tanah tertutup dengan tanaman yang rapat atau lapisan mulsa yang tebal, variasi dan fluktuasi suhu tidak terlalu besar dan fluktuasi suhu tidak menembus lapisan tanah yang dalam

3. Suhu tanah mempunyai efek langsung terhadap pertumbuhan tanaman dan juga mempengaruhi aktivitas mikroba tanah;

4. Freezing and thawing of the soil water also affects soil structure. Slow and occasional freezing and thawing (like under mulch) is beneficial for soil structure.

TEMPERATUR TANAH

1. Warna tanah dapat mengisyaratkan sifat-sifat lainnya. 2. The color of a surface soil horizon depends mainly on its

organic matter content – the darker the soil, the more organic matter it contains. This organic matter imparts favorable properties to the soil, such as better aggregation and a high water-holding capacity. Also, dark soils absorb more radiation during the day, and radiate more heat during the night.

3. Dalam subsoil, warna tanah menyatakan kondisi kebasahan dan aerasi tanah.

4. Umumnya, subsoil yang kemerahan dan kecoklatan mencerminkan aerasi yang bagus dan tidak ada (sedikit saja) genangan air

5. Warna kelabu dan olive menyatakan kondisi genangan air dan reduksi kimiawi besi.

6. A mottled subsoil, one with a splotchy pattern of brownish and grayish colors, is indicative of a fluctuating ground water table.

WARNA TANAH

Munsell Color System• Defined color in terms of Hue, Value and Chroma. • Hue was defined as the actual color, red, blue,

green, etc. • Value was defined as how light or dark a color is. • Chroma was defined as how strong or weak a color

is. • Soil scientists use the Munsell Color book to

determine the color of the soil to help determine in what type of soil it is along with using texture.

BAHAN ORGANIK

TANAH

• Jaringan tumbuhan dan binatang yang telah mati

• Mengandung carbon

BAHAN ORGANIK TANAH = BOT

TIPE BAHAN ORGANIK

1. Kompos2. Seresah sisa-sisa tumbuhan3. Mulsa untuk menutupi

permukaan tanah, membantu menyimpan air tanah dan mencegah pertumbuhan gulma

4. Jerami sisa panen tanaman5. Gambut6. Pupuk Hijau

BIOLOGI TANAH

BIOLOGI TANAH

• Organisme hidup dalam tanah• Termasuk mikro dnd makro flora dan fauna.

Tumbuhan:– Mikro-flora

• Bacteria• Fungi• Actinomycetes

– Makro – akar tanaman

Fauna:– Mikro fauna

• Nematoda• Protozoa

– Makro fauna• Cacing tanah• Rodents (prairie dogs, moles, gophers, etc.)• Arthropods (mites, insects, spiders, etc.)• Gastropods (slugs, snails, etc.)

BIOLOGI TANAH

BIOLOGI TANAH: JARING-JARING MAKANAN

• Macroflora

• Microflora

• Macrofauna

Vascular plants, mosses (autotrophs)

Vascular plants (root hairs), algae, actinomycetes, bacteria, and fungi (auto- and heterotrophs)

Vertebrates, arthropods, earthworms, snails… (herbivores, detritivores, predators)

• Mesofauna

• Microfauna

Arthropods, worms (detritivores, predators)

Nematodes, protazoa… (detritivores, fungivores, bacterivores, predators)

ORGANISME TANAH

A cup of soil contains...

Bacteria

Fungi

Protozoa

Nematodes

Arthropods

Earthworms

{

{

{

Microfauna

Macro- and mesofauna

200 billion

100,000 meters

20 million

100,000

50,000

<1

Microflora, or “microbes”

Immobile organisms all primarily found in the rhizosphere, the zone of soil closest to plant roots

1. Heterotrophs (bacteria, fungi) & autotrophs (algae, cyanobacteria)

2. Dekomposer utama3. Melepaskan unsur hara yang tersedia bagi tanaman

4. Menstabilkan agregat (gumpalan) tanah

MIKROFLORA TANAH

Aggregat tanah diikat bersama oleh:– Hifa fungi– “Glues” bakteri– Bahan organik

sand

silt

hyphaeclay

bacteria

Sumber:

• Agen pelapukan yang utama dalam lingkungan tanah masam

• Jaringan hifa: memperbaiki struktur tanah• Dekomposisi selulose• Dapat bersaing dengan tanaman untuk mendapatkan

nitrogen dari tanah

FUNGI TANAH

1. Ada dalam tanah-tanah hutan dan tanah pertanian2. Ada yang bersifat Aerobik, anaerobik, dan fakultatif3. Ada yang bersifat Autotrofik dan heterotrofik

4. Most do best under high Ca2+, high pH5. Do best when soil temp 20-40C (68-100F) but

seldom killed by temperature extremes

Microflora –BAKTERI TANAH

Fungi vs. Bakteria

Fungi Bakteria

Tubuhnya seperti tabung (benang); hifa

Aerobik

Umumnya pertumbuhannya lebih lambat

Ber-sel tunggal, dapat membentuk koloni

Ada spesies yang bersifat Aerobik, anaerobik, dan fakultatif

Waktu regenerasinya cepat (jam-jama an); respon cepat terhadap

penambahan hara ke tanah

Amoebae

Ciliate

Flagellate

Nematode

• Heterotrof; beberapa parasitik

• Memangsa bacteria dan fungi

• Melepaskan hara tanaman dalam proses mineralisasi (dekomposisi) bahan organik tanah – protozoa KEY for N

Nematode

MicrofaunaMIKROFAUNA TANAH

Sumber referensi: ………

– Banyak ditemukan dalam tanah-tanah hutan– Kelompok-kelompok Saprofitik dan parasitik

– Beberapa spesies predator menyerang akar pohon dan menyebabkan kerusakan

NEMATODES (non-segmented, round worms)

– Fauna tanah yang paling banyak jumlahnya– Ber-sel tunggal– Memangsa bakteri– Up to 30% of all mineralized N from protozoa

PROTOZOA TANAH

1. Heterotroph (detritivora, predator)

2. Memangsa fungi, protozoa, nematoda, mite

3. Penting dalam mengendalikan populasi jenis-jenis yang lebih kecil

MESOFAUNA TANAH

1. Heterotrophs

2. “shred” material tumbuhan

3. Memangsa bakteria dan fungi yang berhubungan dnegan bahan organik

MAKROFAUNA TANAH

1. Probably the most important component of soil fauna (not in acid soils, not in very dry soils)

2. Pass as much as 30 tons/ha of soil through their bodies each year

3. Menghasilklan kotoran cacing yang kaya hara N, P, K, Ca, Mg, pH, dan KTK

4. Membantu pembentukan struktur tanah yang baik dan aerasi tanah.

CACING TANAH

KOTORAN CACING TANAH vs. TANAH

Characteristic Earthworm casts Soils

silt & clay (%) 22.2

Bulk density (g/cm3) 1.28

Structural stability 65

CEC (cmolc/kg) 3.5

38.8

1.11

849

13.8

Influence of soil biota on soil processesNutrient cycling Soil structure

Microflora

Microfauna

Mesofauna

Macrofauna

Break up O.M., mineralize and immobilize nutrients

Bind aggregates, hyphae entangle particles

Regulate bacterial and fungal populations

Indirectly affect structure

Regulate above pops.; fragment plant tissue

Fecal pellets, pores

Fragment plant tissue Mix O.M. and mineral soil; pores; feces

Ecosystem Function –

Rate of decomposition depends on:• Physical and chemical nature of the litter material • Temperature and moisture of the soil environment• Aeration (vs. anaerobic)• The kinds and numbers of soil fauna

More bugs, and more different kinds of bugs, means more decomposition

FUNGSI EKOSISTEM TANAH

KIMIA TANAH

SIFAT KIMIA TANAH

Kemampuan tanah menyediakan hara esensial bagi tanaman mencakup:

1. Ketersediaan unsur hara2. Sifat kimiawi lainnya:

– Mineral liat– Kandungan humus– Kation tukar– Reaksi tanah (pH).

HARA TANAMAN YANG BERASAL DARI UDARA DAN AIR

• Carbon• Hydrogen• Oxygen Tanaman menyerap CO2 dari udara melalui

stomata daun (mulut daun)

Tanaman menyerap air (H2O) dari dalam tanah melalui bulu akar (root hairs)

CO2 dan H2O digunakan oleh tanaman dalam proses fotosintesis yang berlangsung dalam

khlorofil.

NitrogenKALIUM

FOSFOR

HARA PRIMER

Sulfur

Magnesium

Calcium

HARA SEKUNDER

• Boron• Chlorine• Copper• Iron• Manganese• Molybdenum• Zinc

HARA MIKRO

• Boron• Calcium• Carbon• Chlorine• Copper• Hydrogen• Iron• Magnesium

ManganeseMolybdenumNitrogenOxygenPhosphorusPotassiumSulfurZinc

16 HARA ESENSIAL

• Nitrogen (N): unsur hara sangat penting yang menentukan laju pertumbuhan tanaman– Gejala defisiensinya: daun menguning

• Phosphorous (P): required during germination and fruit/seed formation– Deficiency symptoms: stunted growth; purple-colored

leaves

• Potassium (K): fungsi regulator– Gejala defisiensinya: Pertumbuhan kerdil; daun

berbecak-becak.

FUNGSI HARA PRIMER &GEJALA DEFISIENSI HARA

MENGAPA MEMPELAJARI HARA DALAM TANAH ?

1. Untuk memaksimumkan hasil tanaman2. Untuk memaksimumkan keuntungan3. Untuk memelihara kesuburan tanah

MENENTUKAN KESUBURAN TANAH

Metode untuk menentukan kesuburan tanah :• Uji tanah = soil test• Pengelolaan bahan organik• Pemupukan.

pH = Kemasaman tanah

1. Ukuran kemasaman atau kebasaan, nilainya 0 - 14

2. Acid – pH < 7.03. Alkalis – pH > 7.04. Most organic matter is acid5. Most artificial media is neutral6. Ideal pH for most ornamental plants and

lawn or turf grasses is 5.5 to 7.0

Sumber: Brady and Weil (2002)

Neutral

pH = Kemasaman tanah

pH = - log (H+ ion concentration)

Brady and Weil, 2002

As pH increases…As pH decreases…

pH = 7neutral

Setiap jenis tanaman memerlukan kisaran pH optimum tertentu

Bentuk-bentuk kemasaman tanah

pH tanah merupakan ukuran kemasaman aktif

Kemasaman Cadangan = Potensial

Active acidity

Sumber: Brady and Weil, 2002

exchangeablecations

soil solution

Humus

Clay

-

-

--

-

-

--

--

Al+3

Ca+2

H+

K+

Ca+2

Mg+2

K+

H20 H20

H20H20

H20

+SO4

-2 +--

H20

Apa “Kejenuhan Basa” ?

Exchangeableacidity

Reaksi kesetimbangan ion-ion dalam tanah

+ H2O ↔ Al(OH)3 + 3H+

Apakah pH berhubungan dengan kenenuhan basa ?

100 80 60 40 20 0 Acid Saturation, %

Muatan-listrik yang tergantung pH

The dominant clay minerals in IL have mostly permanent

charge

Sumber: Brady and Weil (2002)

Muatan tergantung pH

Kation H+ mengalami disosiasi kalau pH tanah naik, dan kation H+ mengalami re-asosiasi kalau pH turun.

Muatan pada substansi humik (dan liat yg

aktivitasnya rendah) sangat tergantung pH

Proses yang menghasilkan H+ ke tanah:

1) Asam karbonat terbentuk ketika CO2 larut dalam air. Kation H+ dilepaskan kalau asam karbonat berdisosiasi:

H2CO3 → HCO3- + H+

2) Organic acids form during the decomposition of organic matter. H+ ions are released when these organic acids dissociate.

3) Sulfuric and nitric acids form during the oxidation of reduced forms of N and S (e.g., NH4

+ from fertilizer, elemental S). NH4

+ + O2 → NO3- + 2H+ S0 + O2 → SO4

-2 + 2H+

4) Sulfuric and nitric acids form when sulfur oxides and nitric oxides (released into the atmosphere by automobile emissions, industry smoke stacks, volcanoes, forest fires) dissolve in precipitation. H2SO4 and HNO3 are strong acids and fully dissociate in water.

5) Akar tanaman melepaskan H+ untuk menjaga keseimbangan muatan-listrik internal ketika proses penyerapan kation melebihi penyerapan anion.

Proses-proses yang memerlukan kation H+ dalam tanah:

1) Pelapukan mineral (mis. silicates, carbonates…)

2) Dekomposisi anion organik

3) Reduksi bentuk-bentuk oksidatif dari N, S dan Fe.

4) Roots release OH- or HCO3- to balance internal charge when anion uptake

exceeds cation uptake

5) Inner sphere adsorption of anions (especially sulfate) which displaces hydroxyl (OH-) groups

Sumber: Chadwick and Chorover ( 2001)

Sumber-sumber penyangga pH dalam tanah

Carbonates

Hubungan pH dengan kejenuhan Al

K+

H+

NO3-

?

pH rhizosfir tanaman berubah karena

tanaman mengendalikan

keseimbangan muatan-listrik internalnya.

Rhizosfir = zone di sekitar permukaan akar tanaman

Pertumbuhan tajuk seimbang dengan pertumbuhan akarnya

Wassalam ……

…... dst …..

Foto: smno.hutanjati.saradan.jan2013