1. MIKROORGANISME & BAHAN ORGANIK TANAH
AGROTEKNOLOGI

3. 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 & amoeba
One 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

4. Soil Organisms Significance/Fungsinya
1. 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

5. Soil Organisms Cont. Kind
1. Plant
2. Animal
Plants ( bacteria, actinomycetes, fungi, algae)
1. Bacteria
1. Very small single celled organisms
2. Multiply by elongation and dividing into 2 parts
3. Millions or even billions per gram of soil

6. 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 respiration
Don’t need
Host Plant

7. Azotobacter More common in forest soils Optimum Reaction pH 6.9 - 7.3
Clostridium
More common in forest soils
Optimum Reaction pH
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

8. 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

9. 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

10. Cont. 1. Bacteria using nitrogen compounds as an energy source
a. Nitrosomes
- oxidize ammonium Nitrite
- NH NO2-

11. 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

12. SOIL MICROORGANISM Bacteria Pseudomonas Arthrobacter Bacillus
Ed Basgall
UBC EM facility
Pseudomonas
Arthrobacter
CIMC
Bacillus
Travis & Gugino - PSU

13. II. Actinomycetes Unicellular micro-organisms
Transitional between the bacteria and fungi
Effect of soil pH
a. Sensitive to acid soil- no activity below pH 5.0, optimum activity between
Heterotropic Feeders- breaks down organic matter and humus liberating nutrients, especially nitrogen
form NH3

14. Actinomycetes Streptomyces SSSA Paul R. August Univ of Iowa
Travis & Gugino - PSU

15. Nitrogen Cycle

16. 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

17. 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

18. Fungi Microorganisms Aspergillus Trichoderma Fusarium PSU Em facility
K.J. Kwon-Chung
PSU Em facility
D.C. Straney
Fusarium
Travis & Gugino - PSU

19. Mycorrhizae

20. 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

21. 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

22. Nematodes

23. Many beneficial effects from activities of microorganisms
Microorganisms produce:
Plant growth hormones
Stimulate plant growth hormones
Compete with disease organisms

24. SOIL ORGANIC MATTER
(BAHAN ORGANIK TANAH)

25. Soil Components The 4 parts of soil
About ½ of the soil volume is solid particles
About ½ of the soil volume is pore space
Recall that soil is made up of 4 parts: mineral matter, organic matter, water, and air.
A good agricultural soil will be about half solid particles and half pore space. Some of the pore space will be filled with air and some of it with water, depending on how wet or dry the soil is.
The solid part of soil is mostly mineral material in most agricultural soils. But, notice that organic matter is a very small part of the soil, only 1 – 5% of most soils. So, if soil organic matter is such a small fraction of the soil, why should we be concerned about it?

26. 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.

27. SOIL ORGANIC MATTER Fresh residues Decomposing organic matter
Soil Organic matter encompasses all organic components of a soil:
Fresh residues
Decomposing organic matter
Stable organic matter
Living organisms

28. Composition of green tissue 75% is water
of dry matter in mature plants
Sugars and starches 1-5%
Carbohydrates Hemicellulose %
Cellulose %
Fats, waxes, tannins, etc %
Lignin's %
Proteins Simples water soluble 1-15%
and crude protein

29. Changes of Organic Compounds in the Soil
I. Compounds Characteristic of Fresh Plant Tissue
Decompose with difficulty Decompose easily
Lignin Cellulose
Fats Starches
Oils Sugars
Resin Proteins

30. 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

31. - Burning process - oxidation
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

32. The Carbon Cycle - cycle of life energy cycle CO2 Animal To Atm.
Green Manure
& Crop Residue
Farm Manure
Soil Reactions
CO3 , HCO3
Microbial Activity
Carbon
Dioxide
Drainage losses CO2 & Carbonates &
Bicarbonates of Ca, Mg, K, Etc.

33. 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

34. Humus Properties 1. highly colloidal 2. amorphous (not crystalline)
3. cation exchange Cap me/100 gms.
Clay me/100 gms.
4. absorption of water from sat. atmosphere % clay %

35. 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 :1
Thus it can be seen that organic matter contains large amounts of carbon and comparatively small amounts of nitrogen.

36. 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

37. 3. High cation adsorption
- 2 x 20 x clay
% adsorbing power of mineral
soils
4. Supply and availability of nutrients
- N, P and S held in organic forms
- Manure ( )/ ton ( ) N P K Available

38. QUANTITY IN SOILS SOM in mineral soil up to 18% by weight
Typically 0.5 to 5%.
SOM > 18% in organic soils
SOM 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

39. How is SOM Measured? Testing for Soil Organic Carbon
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

40. 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)O > 4Cr CO2 + 11H2O
Titrate excess Cr2(VI)O72- with Fe2+
Not used much any more

41. Components of SOM

42. KESIMPULAN
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
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).
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.
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).