MIKROORGANISME&

BAHAN ORGANIK TANAH

AGROTEKNOLOGI AGROTEKNOLOGI

In 1 teaspoon of soil there are…In 1 teaspoon of soil there are…

Bacteria 100 million to 1 billion

Fungi 6-9 ft fungal strands put end to end

Protozoa Several thousand flagellates & amoebaOne to several hundred ciliates

Nematodes 10 to 20 bacterial feeders and a few fungal feeders

Arthropods Up to 100

Earthworms 5 or more

Travis & Gugino - PSU

Soil Organisms

Significance/Fungsinya1. Decomposition of plant and animal residues

2. Release of nutrients and inorganic elements which feed plants and cause mineral weathering

3. Synthesis of new organic compounds

4. Humus formation to increase cation exchange and structure

5. Nitrogen fixation

Soil Organisms Cont.Kind

1. Plant

2. Animal

Plants ( bacteria, actinomycetes, fungi, algae)

1. Bacteria1. Very small single celled organisms

2. Multiply by elongation and dividing into 2 parts

3. Millions or even billions per gram of soil

I. Classification of Bacteria (Heterotropic)

A. Heterotropic obtain their carbon and energy from various organic compounds

1. Nitrogen fixing derive their nitrogen in gaseous form from the atmosphere or they can obtain their nitrogen from Ammonia or Nitrates

a. Non Symbiotic - those that are free living

1. Anaerobic organisms - those not needing free oxygen for

respirationDon’t need Host Plant

Clostridium– More common in forest soils– Optimum Reaction pH 6.9 - 7.3– no fixation below pH 5.0

2. Aerobic- need free oxygen

Azotobacter

– More common in agriculture soils– Very sensitive to acidity– pH below 5.5 to 6.0 no fixation

b. Symbiotic - live on host plant to mutual advantage

Rhizobium

- Find on nudules

- Nitrogen from the air

c. Aerobic Bacteria- requiring combined Nitrogen

Bacillus mycoides

- Cause denitrification

d. Anaerobic Bacteria - which require combined Nitrogen

- Nitrates ---------- Nitrites, ammonia

- Sulfates ---------- Sulfites, sulfides

Classification of Bacteria (Autotrophic)

B. Autotrophic- derive their carbon primarily

from CO2 of the atmosphere and their

energy from the oxidation of inorganic

compound or simple compounds of

carbon

1. Bacteria using nitrogen compounds as an energy source

a. Nitrosomes

- oxidize ammonium Nitrite

- NH4+ NO2

-

Cont.

Cont.b. Nitrobacter

- Oxidize Nitrite to Nitrate

- NO2- NO3

-

- little or no activity below a pH of 6.0

- little or no activity below a temp of 65oF

2. Bacteria using sulfur or sulfur compounds as energy sources.

a. Thiobacillus

S + O2 + H2O H2SO4

SOIL MICROORGANISM

BacteriaBacteria

UBC EM facility

Ed Basgall

CIMC

Pseudomonas

ArthrobacterBacillus

Travis & Gugino - PSU

II. ActinomycetesUnicellular micro-organisms

Transitional between the bacteria and fungi

Effect of soil pHa. Sensitive to acid soil- no activity below pH 5.0,

optimum activity between 6.0 - 7.5

Heterotropic Feeders- breaks down organic matter and humus liberating nutrients, especially nitrogen

form NH3

ActinomycetesActinomycetes

SSSA

Univ of Iowa

Paul R. August

StreptomycesTravis & Gugino - PSU

Nitrogen Cycle

III. Fungi

Heterotropic organisms

Fungi will tolerate a wide pH range– abundant in acid soils where bacteria and

actinomycetes offer only limited competition

Activities of Fungi– Decompose organic residues

Fungi Cont.

Micorrhiza- fungus roots

more common in forest soils

fungal roots form a mat around the absorbing root while others penetrate the root cells– Symbiotic relationship- help with nutrient

absorption by increasing absorptive surface– Pine seedlings will not grow well without them

MicroorganismsMicroorganisms

FungiFungi

PSU Em facility

Trichoderma

Aspergillus

FusariumD.C. Straney

K.J. Kwon-Chung

Travis & Gugino - PSU

MycorrhizaeMycorrhizae

IV. Algae

minute plants which are photosynthetic

found in surface soils but in low amounts

Blue green types are important in wet soil

– fix nitrogen in rice paddies

– give off oxygen to the water

Soil Macro Animals

Include- rodents, insects, millipedes, centipedes, earthworms

Earthworm- most important macro animals– may pass as much as 15 tons of dry earth per

acre through their bodies

Micro-organisms and the nitrogen cycle

Organic matter of mineral soils

Source- remains of plants and animals

NematodesNematodes

Many beneficial effects from activities of microorganisms

• Microorganisms produce:– Plant growth hormones

– Stimulate plant growth hormones

– Compete with disease organisms

•SOIL ORGANIC MATTER(BAHAN ORGANIK TANAH)

Soil ComponentsThe 4 parts of soil

MineralMatter45%

SoilWater25%

SoilAir

25%

OrganicMatter

5%

About ½ of the soil volume is solid particles

About ½ of the soil volume is pore space

Soil Organic Matter

• SOM consists of a broad spectrum of chemical classes, including amino acids, lignin, polysaccharides, proteins, cutins, chitins, melanins, suberins, and paraffinic macromolecules, as well as organic chemicals produced by humans.

SOIL ORGANIC MATTER

Soil Organic matter encompasses all organic components of a soil:

1. Fresh residues2. Decomposing

organic matter

3. Stable organic matter

4. Living organisms

Composition– of green tissue 75% is water– of dry matter in mature plants

Sugars and starches 1-5%

Carbohydrates Hemicellulose 10-28%

Cellulose 20-50%

Fats, waxes, tannins, etc 1-8%

Lignin's 10-30%

Proteins Simples water soluble 1-15%

and crude protein

Changes of Organic Compounds in the Soil

I. Compounds Characteristic of Fresh Plant TissueDecompose with difficulty Decompose easily

Lignin Cellulose

Fats Starches

Oils Sugars

Resin Proteins

II. Complex Intermediate Products of Decay

Resistant compounds Decomposition compounds

Resigns Amino acids

Waxes Amides

Oils and Fats Alcohols

Lignin Aldehydes

III. Products of Soil-Decomposition Processes

Resistant complex Simple end products

Humus- a colloidal complex carbon dioxide and water

nitrates, sulfates

phosphates,

calcium compounds

Rate of Decomposition

- Burning process - oxidation

1. Sugars - Starches - simple proteins Rapid

2. Crude proteins

3. Hemicellulose

4. Cellulose

5. Lignins, fats, waxes Very Slow

The Carbon Cycle

Soil Reactions

CO2

Animal

Farm ManureGreen Manure& Crop Residue

To Atm.

Microbial Activity

CarbonDioxide

CO3 , HCO3

Drainage losses CO2 & Carbonates & Bicarbonates of Ca, Mg, K, Etc.

- cycle of life energy cycle

Humus

Humus is a mixture of complex compounds and is not a single material. These compounds are either (a) resistant materials (b) compounds synthesized within microbial tissue.

Definition- Humus is a complex and rather resistant mixture of brown or dark brown amorphous and colloidal substances that have been modified from the original tissue or have been synthesized by various soil organisms

Humus Properties

1. highly colloidal

2. amorphous (not crystalline)

3. cation exchange Cap. 150-300 me/100 gms.

Clay 8-100 me/100 gms.

4. absorption of water from sat. atmosphere 80-90% clay 15-20%

Carbon : Nitrogen Ratio

Carbon : Nitrogen ratio fairly constant in soils– in cultivated soils 10 or 12:1 is a common ratio– in plant material Legumes 20:1

Straw 90:1

Sawdust 150:1

Thus it can be seen that organic matter contains large amounts of carbon and comparatively small amounts of nitrogen.

Influence of Soil Organic Matter on Soil Properties

1. Soil Color - brown to black

2. Influence on physical properties

- granulation encouraged

- plasticity cohesion reduced

- H2O holding capacity increased

3. High cation adsorption

- 2 x 20 x clay

- 30 - 90% adsorbing power of mineral

soils

4. Supply and availability of nutrients

- N, P and S held in organic forms

- Manure (10 - 5 - 10)/ ton (5 - 1 - 5) N P K Available

QUANTITY IN SOILS

SOM in mineral soil up to 18% by weight– Typically 0.5 to 5%.

SOM > 18% in organic soilsSOM about 50% C

– SOM = (OC)(factor) where the factor = 1.8 to 2.0• For most estimations 2 is a good round number

– Older books use a factor = 1.724

How is SOM Measured?

SOM is usually measured in the laboratory as organic carbon,

Soil organic matter is estimated to contain 58% organic carbon (varies from 40 to 58%) with the rest of the SOM comprising of other elements (eg, 5% N, 0.5% P and 0.5% S).

A conversion to SOM from a given organic carbon analysis requires that the organic carbon content be multiplied by a factor of 1.72 (1.00/0.58).

Thus, 2% SOM is about 1.2% organic carbon.

Testing for Soil Organic Carbon

Walkley Black• Oxidize SOM to CO2 using acid dichromate

• Assume C is in the zero oxidation state as in carbohydrates (CH2O).

3CH2O + 16H+ + 2Cr2(VI)O72- --> 4Cr3+ +

3CO2 + 11H2O

Titrate excess Cr2(VI)O72- with Fe2+

• Not used much any more

Components of SOM

KESIMPULAN1. Roles of Soil organisms : Decomposition of plant and animal

residues, Release of nutrients and inorganic elements, synthesis of new organic compounds, Humus formation, Nitrogen fixation

2. Soil organic matter : all living organisms (microorganisms, earthworms, etc), fresh residues (old plant roots, crop residues, recently added manures), decomposing organic matter and stable organic matter (humus).

3. Influence of Soil Organic Matter on Soil Properties : Soil Color - brown to black, Influence on physical properties (granulation , plasticity , H2O holding capacity ), High cation adsorption, Supply and availability of nutrients.

4. SOM is usually measured in the laboratory as organic carbon, A conversion to SOM from a given organic carbon analysis requires that the organic carbon content be multiplied by a factor of 1.72 (1.00/0.58).