Introduction and imp. of organic matter, composition, types of organic matter, C:N ratio, Sources of organic crop residues, Recycling

1. 1
BINM: Organic manures

2. Importance of Organic Manures
Soil makes living
system
Food for soil flora &
fauna
Store house for
nutrients
Improves chemical
properties
Improves physical
properties of soil
Improves buffering
capacity of soil
Releases nutrients
from soil minerals

7. Basic Definitions
Decomposition Biochemical breakdown of organic wastes (crop residues, plant
originated waste, sewage/sludge) or conversion of complex
organic compounds into simpler compounds often
accomplished by microbial metabolism
Compost Organic residues which have been mixed, piled and moistened,
with or without addition of fertilizer or lime and generally
allowed to undergo mesophilic (30-40oC) and thermophilic (50-
60oC)decomposition until the original organic material are
substantially altered or decomposed.
Organic
recycling
Returning of plant nutrients removed by the crops from soil
through addition of organic material of crops after harvesting
is referred as organic recycling
C:N ratio It’s a ration of the mass of carbon to the mass of nitrogen in a
substrate. (Relative quantity)
C:N ration 10:1 means there is a ten units of carbon for each
unit of nitrogen in the substrate and it indicate suitability of
particular organic material for making compost along with its
period.

9. Carbohydrate 60-70%
Ash 5%
Chemical composition of undecomposed organic
matter

12. Organic Matter
Easily degradable
Simple sugars, amino acids
& amides
CO2,H2O NH3 etc
Moderately degradable
Cellulose, hemicellulose,
protein complex
carbohydrates
Simple compounds like
sugars amino acids
quinoids etc
Difficultly degradable
Tannins, lignin's, keratins,
chitin
Complex substances like
quinines, polyphenols etc

13. Organic matter/organic material/natural organic matter
Refers to the large source of carbon based compounds found
within natural and engineered, terrestrial and aquatic environments. It
is matter composed of organic compounds that have come from the
remains of organisms such as plants and animals and their waste
products in the environment.
Organic molecules can also be made by chemical reactions that don't
involve life. Basic structures are created from cellulose, tanins, chitin,
and lignin, along with other various proteins, lipids, and carbohydrates.
Organic matter is very important in the movement of nutrients in the
environment and plays a role in water retention on the surface of the
planet.

14. Sources of organic
matter
Primary sources
Plant origin like wheat
straw, sugarcane trash,
groundnut cake, castor
cake etc.
Secondary sources
Animal origin like cow
dung, urine, night soil,
bone meal
Organic Recycling
Returning of plant nutrients removed by the crops from soil through
addition of organic material of crops after harvesting of crops is referred
as ….

15. Organic sources based on their
occurrence
Rural residues
Farm waste, dry
leaves of plants
Urban waste
Night soil, sewage,
sludge, city waste etc
Industrial waste
Sugar, dairy, paper,
alcohol industrial
waste etc.

16. CO2, H2O, More
energy, more
biomass
CO2 + CH4+Alcohol +
NH3 + H2 + Less
energy Less biomass
Extracellular enzymes
Complex polymers
Cellulose/lignin/proteins
(High molecular weight
substances)
Monomeric units like
sugars, amino acids, phenols
or Low molecular weight
substances
Decomposition process

18. C:N ratio
It is defined as the ratio of the weight of organic carbon
to the weight of total nitrogen in the soil or organic
matter. It is the relationship between organic matter and
nitrogen content of soils or plants.
Carbon is present in the form of organic matter or humus.
Carbon content varies from 1% in coarse textured soils to 3.5 % in
grassland soils
Poorly drained soils (Aquepts) may contain 10% or more carbon
Ideal C:N ration is between 10:1 to 12:1

19. Organic matter & Nutrient interaction
in soil favors…..
•Plant and animal residue upon degradation
provides N/P/S and micronutrients
•Microbial biomass serves as nutrient storage
•Conversion of organic N/P/S to soil available
nutrients through microbes
Organic
N/P/S
NH4/PO4
3-
/SO4
2-
Mineralization
Immobilization

20. Crop Residues C:N Ratio
Legumes and young green leaves 10:1 to 30: 1
Sugarcane trash 100 : 1
Saw dust 600:1
Bacteria/Fungi/Actinomycets 5:1 to 10:1
Cultivated soils 8:1 to 15:1

21. Importance of C:N ratio…..Pertaining to soil
• When organic residues with wider C:N ratio - added to
soil, competition between plant & microbes for N
Example: Residues > 300:1 C:N ratio
• Heterotrophic microbes become active and increase
their population with production of more CO2 through
their respiration
• Under these conditions, the NO3-N level in soil
decreases as microbes utilize the native soil N
• N-is immobilized at the initial stages and is not
available to plant
• Addition of plant residues with high C:N, C:P or C:S ratio
favors initial net immobilization followed by
mineralization

22. Importance of C:N ratio…..Pertaining to soil
• Wider C:N ratio (more than 40) in substrates such as oat
straw or any other promote immobilization of available
N in the soil/compost, resulting in a slowing of the
decomposition due to limited N availability.
• Addition of external N/P enhances the rate of
decomposition in soil/ during composting.
• Metabolic processes during composting further affect
the pH of the material.
• Compost microorganisms operate best under neutral to
acidic conditions, with pH's in the range of 5.5 to
8. During the initial stages of decomposition, organic
acids are formed. ... As composting proceeds, the
organic acids become neutralized, and
mature compost generally has a pH between 6 and 8.

24. Organisms Temperature range
Psychrophiles of 0–15 °C
Psychrotrophs 4°C and 25 °C
Mesophiles 20 °C to about 45 °C
Thermophiles above 50 °C.
Temperature Range for Microbes

26. Importance of C:N ratio…..Pertaining to soil
•C:N ratio indicate suitability of particular
organic residue for making compost and also
helps to decide period of decomposition
•Microbes require N for synthesis of amino acids
and proteins (immobilization) thus in wider C:N
ratio organic material N is limiting factor for the
growth of microbes hence require more time
for decomposition.

30. C:N Ratios as Related to Organic Matter
Decomposition
If C:N ratio
30:1 Immobilization
< 20:1 Mineralization
20-30:1 immobilization = mineralization

31. Effect of C:N ratio on CO2 evolution
Crop residues with LOWER C:N ratio……
……. at EARLY stage more microbial activity
and more CO2 evolution and decomposition
rate becomes faster
•Crop residues with HIGHER C:N ratio…………….
at LATER stage CO2 evolution RATE increases
decomposition rate becomes slower
•Wider C:N ratio of crop residues will release
more loss of carbon as CO2 and CH3

32. Effect of C:N ratio on soil availability of
nutrients
If we add crop residues with wider C:N ratio in
the soil – the microbes in soil feed on that
material having carbon but they also need N/P
for biosynthesis of proteins.

33. 1) C:N ratio mainly controls decomposition rate in soil
C:N ratio mainly controls rate of decomposition in soil.
1 WIDE C: N ratio NARROW C: N ratio
2 Slow decomposition rate Fast decomposition rate
3 Immobilization of nutrients Mineralization of nutrients
4 Carbon and energy wastage in
large quantities
Carbon and energy starvation
occur
5 Microbial activity restricted due to
N limitation
Competition among the
microorganism for available N
Ex : Speed of decomposition
becomes slow with more/wide
C/N ratio residue or low N
percentages
Low/narrow C/N ratio or high N
percentages speeds
the decomposition rate.
Importance of C: N ratio

34. 2) It is a source of food and energy for plants
I Soil microbes require carbon for building essential organic
compounds
Ii They also need sufficient N to synthesize N containing cellular
components, such as amino acids, enzymes and DNA
iii Microbes have 8:1 ratio means – microbes must incorporate
into their cells about 8 parts of carbon for every 1 part of N.

35. 3) It controls N availability in soils/plants
I If C/N ratio of OM is about 25:1, the soil microbes will
have to scavenge the soil solution to obtain enough N
Ii Thus, the incorporation of high C/N residues will deplete
the soil native N, causing higher plants to suffer from N
deficiency.
iii While low C/N ratio (<20) Organic matter helps in increase
in N content of soil for plants and organisms.

36. 4) The decay of organic matter can be delayed;
if sufficient nitrogen to support microbial growth is neither
present in the material nor available in the soil
5) Influence of C/N ratio on Soil ecology;
The soil ecosystem consists of saprophytic bacteria and
fungi and nematodes, protozoa and earthworms that grow
rapidly on organic residues as food source.
6) It is related to release of available N, total organic content
and accumulation of humus.

37. Thank you