Upload
ilham-nugroho
View
226
Download
0
Embed Size (px)
Citation preview
7/31/2019 Bab_08 Bahan Organik Tanah
1/20
Chapter 8:
Soil Organic Matter
8.1
7/31/2019 Bab_08 Bahan Organik Tanah
2/20
Organic Materials: Biomass (plant roots,
organisms) Plant/animal/ Residue
(dead but identifiable:
twig, branches, log) Particle size > 2 mm
* Partly decomposedorganic materialsincluded microbes.
* Particle size < 2 mm
* 0 to 6% (by mass) inA horizons
*
7/31/2019 Bab_08 Bahan Organik Tanah
3/20
250 m
150 m
Light
Intermediate
50 mHeavy
SOM Soil + SOM
< 1.13 g cm-3
>1.3 g cm-3
Particle sizeParticle density
SOM:dark & light 8.3
7/31/2019 Bab_08 Bahan Organik Tanah
4/20
The Carbon Cycle
Organic matter decays CO2 is one of theimmediate products
Carbon is the common constituents of all OM and is
involved in essentially all life processesTransformation of this element is called as
Carbon Cycle ~ Biocycle ~ Cycle of life
That makes possible the continuity of life on the earth !
8.4
7/31/2019 Bab_08 Bahan Organik Tanah
5/20
Carbon cycleat plot level
Carbonate &
bicarbonates
CO2
CO2CO2
CO2
CO2
Food
Photosynthesis
CO2
MicrobiaNutrientrelease
Residue
Macrofauna
HumusLeaching
Nutrientrelease
Soilreaction
Soil
surfaceCO2
8.5
7/31/2019 Bab_08 Bahan Organik Tanah
6/20
C cycle at global / lanscape level
8.6
7/31/2019 Bab_08 Bahan Organik Tanah
7/20Litter is worth!, sometimes it does not ! When?
8.7
7/31/2019 Bab_08 Bahan Organik Tanah
8/20
Role of SOM
Physic:
Bind mineral particles into granules
Maintain soil water content
Chemic:
Source of plant nutrients
Maintain Cation Exchange Capacity (CEC)
Detoxify poisonous elements
Biologic:
Energy Source for soil organisms8.8
7/31/2019 Bab_08 Bahan Organik Tanah
9/20
Litter (Serasah):
Dead leaf (Daun gugur )
Twigs (tangkai daun + ranting)
Branches (cabang)
Nutrient Source
Litter
Plant
Roots
8.9
7/31/2019 Bab_08 Bahan Organik Tanah
10/20
Coffee Monoculture,more weeding
Coffee Multistrata ~ thick
surface litter layer ~ lessweeding
P
hotographer:MikeChapman
Photographer:Ku
rniatunHairiah
8.10
7/31/2019 Bab_08 Bahan Organik Tanah
11/20
Water
75%
Drymatter
25%
O2
40%
Ash
8%
H
8%
C44% Carbohydr
ates
60%
Lignin
25%
Protein
10%
Fats,
waxes,
tannins
5%
Sugars & starches (1-5 %)
Hemicelluloses (10-30 %)
Celluloses (20-50 %)
Elemental
composition
Types of
compounds
Composition of green plant materials addedto soils (Organic materials)
Inorganicelements
8.11
CO
7/31/2019 Bab_08 Bahan Organik Tanah
12/20
CO2
60-80 %
Organic
residues100 g
10-
30%
3
8
%
3
8
%
Complex humicNon-humic :polysacharids,polyuronides, acids etc.
Biomass(soilorganisms)
Humus (15-30 %)
8.12
7/31/2019 Bab_08 Bahan Organik Tanah
13/20
Factors affecting soil organic matter
Climatic: Temperature, rainfall
Natural vegetation
Soil texture Soil has a high clay and silt
content, generally much high in soil organicmatter
Soil drainage poorly drained soils high insoil organic matter
Soil & crop management:
tillage, crop rotations etc.
8.13
7/31/2019 Bab_08 Bahan Organik Tanah
14/20
Forest Soil
Agicultural soil
Fertile Soil:
High SOM : ~ > 2.5 4.0 %Low Bulk Density: ~ < 1.3 g cm-3
High biota activity
Generally dark colored
8.14
7/31/2019 Bab_08 Bahan Organik Tanah
15/20
7/31/2019 Bab_08 Bahan Organik Tanah
16/20
Serasah di Hutan
Cassava litter
Forest litter ~
various quality
How fast theorganic
materialsdecompose?
8.16
7/31/2019 Bab_08 Bahan Organik Tanah
17/20
O i M b kd i h i
7/31/2019 Bab_08 Bahan Organik Tanah
18/20
SOIL HUMUS
Compounds inorginal tissue
Organism numbers and rate of releaseof CO2 and H2O
CO2 & H2O release
Synthesis of new compounds
New soilhumus
level
Old soilhumus level
Fresh residuesaddedResidues well
humifiedTime
Organic Matter breakdown with time8.18
7/31/2019 Bab_08 Bahan Organik Tanah
19/20
Humus:
A mixture of complex compounds
Rather resistant mixture of brown or dark brown amorphous& colloidal organic substances
Result from microbial decomposition and synthesis
It has chemical & physical properties of great significance tosoils and plants
Major Characteristics of Humus
Tiny colloidal humus particles (micelles) are composed ofC, H, O.
The surface area of humus coloids per unit mass is veryhigh & negatively charge
8.19
7/31/2019 Bab_08 Bahan Organik Tanah
20/20
The maintenance of soil
organic matter in mineral
soils is the mostimportance challenge to
modern and traditional
agriculture alike.
Photographer : Suyanto, ICRAF, Bogor 8.20