1294 Soil Science Notes

Report
MIKROORGANISME
&
BAHAN ORGANIK TANAH
AGROTEKNOLOGI
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
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
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
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
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
Cont.
1. Bacteria using nitrogen compounds
as an energy source
a. Nitrosomes
- oxidize ammonium Nitrite
NH4+
NO2-
Cont.
b. Nitrobacter
- Oxidize Nitrite to Nitrate
NO2NO3- 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
Bacteria
UBC EM facility
Pseudomonas
Arthrobacter
CIMC
Ed Basgall
Bacillus
Travis & Gugino - PSU
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 6.0 - 7.5
Heterotropic Feeders- breaks down organic matter
and humus liberating nutrients, especially
nitrogen
form NH3
Actinomycetes
SSSA
Paul R. August
Univ of Iowa
Streptomyces
Travis & 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
Microorganisms
Aspergillus
Fungi
Trichoderma
K.J. Kwon-Chung
PSU Em
facility
D.C. Straney
Fusarium
Travis & Gugino - PSU
Mycorrhizae
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
Nematodes
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 Components
The 4 parts of soil
About ½ of the
soil volume is
solid particles
Mineral
Matter
45%
Organic
Matter
5%
Soil
Air
25%
Soil
Water
25%
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 residues
2. Decomposing
organic matter
3. Stable organic
matter
4. Living organisms
Composition
– of green tissue 75% is water
– of dry matter in mature plants
Carbohydrates
Sugars and starches
Hemicellulose
Cellulose
1-5%
10-28%
20-50%
Fats, waxes, tannins, etc
Lignin's
1-8%
10-30%
Proteins
1-15%
Simples water soluble
and crude protein
Changes of Organic Compounds
in the Soil
I. Compounds Characteristic of Fresh Plant Tissue
Decompose with difficulty
Lignin
Fats
Oils
Resin
Decompose easily
Cellulose
Starches
Sugars
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
1.
2.
3.
4.
5.
- Burning process - oxidation
Sugars - Starches - simple proteins
Rapid
Crude proteins
Hemicellulose
Cellulose
Lignins, fats, waxes
Very Slow
The Carbon Cycle
- cycle of life
CO2
energy cycle
Animal
To Atm.
Green Manure
& Crop Residue
Soil Reactions
CO3 , HCO3
Farm Manure
Microbial Activity
Carbon
Dioxide
Drainage losses CO2 & Carbonates &
Bicarbonates of Ca, Mg, K, Etc.
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 8090% 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 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
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
KESIMPULAN
1.
2.
3.
4.
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).

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