mikroorganisme & bahan organik tanah agroteknologi
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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).