for educational purpose

1. INDIRA GANDHI AGRICULTURE UNIVERSITY,
RAIPUR
PRESENTATION
ON
BIOCHEMICAL COMPOSITON &
BIODEGRADATION
OF ORGANIC MATTER
SUBMITTED TO
Dr. R.N.Singh
Dept. Of Soil Science
SUBMITTED BY
Priyanka Sahu
M.Sc.(Ag.) Prev.

2. Soil organic matter
The soil organic matter consist of a whole series
of product which ranges from undecomposed
plant and animal tissue to fairly Amorphous Brown
to black material bearing no trace of the
anatomical structure of the material. That is
normally defined as Soil humus .The native
fraction of soil organic matter is made of a
Heterogenous mixture of polymerized aromatic
molecule. Polysaccharide bound amino acid,
uronic acid polymer and various organic
phosphorus compounds.

3. It protect the soil against erosion and help to
form Good soil structure.
It provide good aeration and better water
movement by loosening the soil.
For achieving maximum benefit, organic matter
must be decomposed and continously
replenished with the addition of fresh organic
material to the soil.

4. Composition of soil organic matter
(1)Organic-
(a)Nitrogenous organic compound-
 Water insoluble – protein ,peptides , peptones other
sulphur carrying compound.
 Water soluble – Nitrate , Ammonical compound.
(b) Non nitrogenous organic compound –
 Carbohydrates – cellulose, Hemicellulose , Starch,
Pectin sugar.
 Lignin – Tannin, Organic acid, essential oil.
 Ether soluble – Fat, oil waxes, resin, steroids.
(2) Inorganic ( Mineral constitute) – Ca, Mg, Na, K ,Fe
Mn, Cu, Zn etc.

6. Decomposition of various organic
compounds
 Different organic residues contain different
group of organic compounds ,so different
groups of compounds have their different case
of decomposition.
 Very slowly decomposed – lignin, Fat,
Waxes, Cellulose and Hemicellulose.
 Rapidly decomposed – Crude proteins,
simple proteins, sugar , starch.

8. Enzymes
 An enzymes is a substance, composed of
protein, that is capable of lowering the activation
energy of other selective compounds , enough to
allow the breaking of a particular bond, under a
particular environment so much reactions
influenced by enzymes are called Biological
reaction.
Urease – Breakdown urea in Ammonium
carbamate.
Protease – By involving water, it the bond linking 2
amino acid to form separate amino acid.

9.  Cellulase – Breaks cellulose which are long
chains sugar units important in decomposition of
organic matter.
 Lignase – Degrades lignin compounds of
decomposed organic residues.
 Hemicellulase – break hemicellulose compound
or organic material.

10. Decomposition of water soluble organic
substances
Inspite of having variation in the composition of
different organic compounds the end product of
decomposition under aerobic condition is more or
less simillar. Sugar and other water soluble
organic nitrogenous compounds are subjected to
decomposition
Sugar + O2 CO2 +H2O
(aerobic cond.)

11. Decomposition of Water insoluble
organic compound
BREAK DOWN OF PROTEIN –
During the course of decomposition of plant materials,
the proteins are first hydrolyzed to a number of
intermediate products and may be represented as
under:
 Hydrolysis Proteases Aas
Proteins Peptones Amides Ammonia
Peptides
Aminization Ammonification
 Aminization: The process of conversion of proteins to
amino acids.
Ammonification: The process of conversion of

12. 2. CELLULOSE – Cellulose is a carbohydrate
composed of Glucose units together in a long
chain.
Cellulose Cellobiose Glucose
Fungus – Aspergilus ,fusarium ,Penicillium
Bacteria – Bacillus ,Pseudomonas
Actinomycetes – Nocardia, Streptomyces
Celluas
e
Cellobias
e

13. 3. HEMICELLULOSE – Hemicellulose are water
insoluble polysaccharides. During breakdown of
hemicellulose the production of single soluble
sugars are found. Hemicellulose attack first by
microorganism that of cellulose compounds. The
enzymes for the breakdown of Hemicellulose
compounds are hemicellulase.
Microbes – Aspergillus , fusarium ,Bacillus ,
streptomyces

14. 4. STARCH – Starch is the polymer of Glucose and
it serve the plant as a storage product. And as
such it is the major serve carbohydrate plant
starches usually contain two component.
Amylase and Amylopectin .
 Amylase – It has a linear structure. Built up of
200-500 or more Glucose units linked together by
an Alpha-1,4-glucosidic bonding.
 Amylopectin – The individual glucose units are
bounded together by Alpha-1,4 linkage but the
molecule is Branched and has side chain
attached through alpha-1,6 glucidic linkage.

15. Starch maltose glucose
Microbes involve – Aspergilus ,fusarium ,
chromobacterium , Nocardia , Streptomyces
amylas
e
Alpha
glucosida
se

16. 5. LIGNIN - Woody type of plant countribute large
amount of lignin . The lignin content of young
plant is relatively low , but the quantity increase
as per plant mature. The rate of lignin
decomposition is affected by
temperature,availability of nitrogen.
Most Fungi can decompose lignin. Lignin is
probably depolymetized to give simple aromatic
substances such as Vanillin and Vanillic acid.
Microbes – Arthobotrys , Humicola ,
pusedomonas , Flavobacterium

17. Factors affecting decomposition of
organic matter
1.Temperature: Cold periods retard plant growth and OM
decomposition. Warm summers may permit plant growth
and humus accumulation
2. Soil moisture: Extremes of both arid and anaerobic
conditions reduce plant growth and microbial
decomposition. Near or slightly wetter than field capacity
moisture conditions are most favorable for both processes.
3. Nutrients: Lack of nutrients particularly N slows
decomposition.

18. 4. Soil PH: Most of the microbes grow best at pH
6 – 8, but are severely inhibited below pH 4.5 and
above pH 8.5.
5. Soil Texture: Soils higher in clays tend to
retain larger amounts of humus.
6. Other Factors: Toxic levels of elements (Al,
Mn, B, Se, Cl ), excessive soluble salts, shade
and organic phytotoxins in plant materials.

19. Reference –
 Das , D.k . Introductory soil science ,fourth
edition , Kalyani publisher
 Rao N. S. subha ,soil microbiology