Bahan Kajian MK. Dasar Ilmu Tanah
PENGELOLAAN
BAHAN ORGANIK TANAH
smno.jurtnh.fpub.nop2013
BO yang diaplikasikan ke tanah
…. Diunduh dari sumber: http://www.soils.wisc.edu/courses/SS325/organic.htm….. 26/10/2012
EFEK BO PADA AGREGASI TANAH
Bacterial cells with a coat of
extracellular polysaccharides (EPS)
are enveloped by clay particles. The
pore space where clays and bacteria
interact, bounded by silt- and sandsize particles, is relatively enriched in
organic matter including EPS residues.
Fungal hyphae are attached to the
outside surface of an aggregate. At
normal soil pH conditions, the cell has
a net negative surface charge.
Most clay particles adhere to the cell
surface by bridging through
polyvalent cations, represented by Mn+
(a) although some may be attached
directly by electrostatic interactions,
either in face-to-face (b), or edge-toface (c) association.
(Sumber: Theng and Orchard (1995).
…. Diunduh dari sumber: http://www.sciencedirect.com/science/article/pii/S0065211303820060……….. 26/10/2012
EFEK BO: Stabilisasi Agregat
A conceptual model of
aggregate hierarchy in
soils where organic
materials play an
important role in the
stabilization of
aggregates.
Sumber: Jastrow and
Miller (1997)
…. Diunduh dari sumber:
http://www.sciencedirect.com/science/article/pii/S0065211303820060………..
26/10/2012
EFEK APLIKASI BO
A model depicting
the dynamics of soil
aggregation and the
roles of particulate
organic matter
(POM) and
microbial
metabolites in the
stabilization of soil
aggregates. From
Baldock (2002).
…. Diunduh dari sumber: http://www.sciencedirect.com/science/article/pii/S0065211303820060……….. 26/10/2012
EFEK APLIKASI BO
Relationships
between soil
organic matter
and soil
fertility.
…. Diunduh dari sumber: http://www.sciencedirect.com/science/article/pii/S0167880906002854 ……….. 26/10/2012
Bagaimana APLIKASI BO
…. Diunduh dari sumber: http://www.organicagriculture.co/soil-fertility-management.php ……….. 26/10/2012
TINDAKAN PENGELOLAAN
UNTUK
MENINGKATKAN KANDUNGAN
BOT
Mengapa BOT harus dipelihara ?
SOM Improves Soil
Physical Properties
– Increased granulation and
aggregate stability
– Makes heavy soils easier
to work
– Increases water
infiltration rates
– Increases water holding
capacity
– Decreases erosion
If your soil looks like this…
You can avoid this!
Mengapa BOT harus dipelihara ?
BOT memperbaiki sifat
kimia tanah
– Increases Cation Exchange
Capacity so the soil is
better able to store and
supply plant nutrients
– Increases pH buffering so
the soil resists changes in
pH
– Reduces Aluminum, Iron,
and Manganese toxicity in
acidic soil
Mengapa BOT harus dipelihara ?
Soil organic matter enhances soil functions and environmental quality
because it:
1. Binds soil particles together into stable aggregates, thus improving
porosity, infiltration, and root penetration and reducing runoff and
erosion;
2. Enhances soil fertility and plant productivity by improving the ability
of the soil to store and supply nutrients, water, and air;
3. Provides habitat and food for soil organisms;
4. Sequesters carbon from the atmosphere;
5. Reduces mineral crust formation and runoff; and
6. Reduces the negative water quality and environmental effects of
pesticides, heavy metals, and other pollutants by actively trapping or
transforming them.
…. Diunduh dari sumber: http://ecomerge.blogspot.com/2010/05/what-is-organic-matter-and-why-it-is.html ……….. 26/10/2012
Apakah BOT ?
Crop residue
• All material in soil that
contains (reduced) carbon.
• SOM is derived from
– Plant residue (both litter and
roots)
– Animal remains and excreta
– Living soil microbes
(microbial biomass)
• Over time microbes
transform fresh organic
material into stable soil
organic matter
Bacteria
Fungi
SOM
Actinomycetes
Tindaklan pengelolaan untuk meningkatkan input bahan
organik ke tanah.
Return more crop residues
Add cover crops
Diversify crop rotations
Add other sources of organic
material
Efek Penambahan bahgan organik terhadap Kandungan BOT
• A 30-yr experiment in Connecticut showed returning corn residues
increased SOM to 4.6%, compared to 3.4% with no residue
returned.
• A rye cover crop will add about 2,000 lb of C per acre from above
ground production and about 500 lb C per acre from roots. After
one year about 500-600 lb of this carbon will likely still be in the
soil.
• An 11-yr study in Vermont showed 20 ton/acre/yr of dairy manure
(13% dry matter) was able to maintain SOM levels at 5.2% in
conventional tilled corn silage production. 30 ton/acre/yr increased
SOM to 5.5%. No manure decreased SOM to 4.3%
Untuk mengurangi kehilangan BOT:
Mengurangi Erosi
Mengurangi olah-tanah
How does tillage affect SOM decomposition?
• Residues are mixed
with soil
– Physically breaks
residue into smaller
pieces
– Intimate contact
between soil and residue
• Aerates soil
• Breaks apart soil
aggregates, exposes
protected SOM to
decomposition
• Promotes erosion losses
Tillage mixes residues into the soil and in so doing it
breaks residues into smaller pieces and puts them into
intimate contact with the soil bacteria and fungi that
are responsible for decomposition.
Decomposition is an aerobic process, and oxidative
process that requires oxygen. It is just like burning
wood in a stove. You can slow down the process by
reducing air flow into the firebox. Open up the
dampers and you can burn a lot more a lot faster.
Tillage does the same in soil. It mixes air (oxygen)
into the soil and greatly speeds up decomposition
because oxygen is usually limiting in the soil.
Some soil organic matter is protected from
decomposition because it is hidden inside soil
aggregates and thus is difficult for microbes and air
to get at it. Tillage breaks apart soil aggregates and so
exposes more organic matter to the agents of
decomposition.
Distribusi Bahgan Organik dalam Tanah pada Kondisi Tanah diolah dan
Tanpa-olah
In CT systems, crop residues and roots get
mixed uniformly through the plow layer so
there is very little change in SOM in the
upper 15 to 20 cm.
In NT systems, crop residues and manures are
left on the soil surface and only mixed by
worms and other soil macroarthropods.
Again, most of these increases are in the
active SOM pool. This is the pool with
highest rates of decomposition and turnover
of material. But since this is the pool that has
the greatest influence on soil aggregation and
stability and water infiltration and ease of root
extension, it is actually desirable to have this
large active pool located near the soil surface.
5
No-till
10
Depth (cm)
This means that most added organic materials
decay near the soil surface and consequently
SOM concentrations are greatest at the
surface and decrease with depth. There is
actually very little difference between the two
systems deeper in the profile.
0
15
Conventional
Tillage
20
25
30
35
5
10
15
20
Soil Organic Carbon (g/kg)
25