The document discusses the important role of soil microorganisms in nutrient management and cycling. It explains that microbes are actively involved in decomposing organic matter, producing humus, and increasing the availability of nutrients like phosphorus. Certain microbes also support plant growth by producing vitamins, hormones, and stimulating natural defenses against pathogens. Microorganisms are key players in soil carbon, nitrogen, phosphorus, and sulfur cycles through processes like nitrogen fixation, nitrification, denitrification, and mineralization. The document also discusses different types of biofertilizers containing beneficial microbes.

1. IMPORTANCE OF SOIL MICROORGANISMS IN
NUTRIENT MANAGEMENT
Presented By:
K.Santhiya
2016-11-095

3.  Active role in nutrient cycling
 Decomposition of the organic matter
 Soil microbes create humus
 Certain soil microorganisms such as mycorrhizal fungi
increase the availability of mineral nutrients (e.g. phosphorus)
 Microorganisms improve the fertility status of the soil and
contribute plant growth-biofertilizers
 microorganisms produce - vitamins and plant
hormones(phytostimulators)
 soil microorganisms are pathogenic to plants and may cause
considerable damage to crops

4.  Antagonism against plant pathogens competition for nutrients
and production of secondary metabolites (antimicrobial
metabolites and antibiotics) and extracellular enzymes
 soil microorganisms produce compounds stimulate the natural
defense mechanisms of the plant and improve its resistance to
pathogens ( biopesticides)
 Azospirillum induces the proliferation of plant root hairs which
can result in improved nutrient uptake
 Mycorrhizal fungi colonize the root systems of many plants and
aid in the uptake of nutrients by the plant, thereby improving
plant growth and overall health

5.  Soil microbes create soil structure, fix nitrogen, control pests
and diseases
 Dehydrogenase enzyme is often used as a measure of any
disruption caused by pesticides, trace elements or management
practices to the soil, as well as a direct measure of soil
microbial activity.

8. Role of Microorganisms in Carbon Cycle
 Many fungi , bacteria attack cellulose and release carbon
 Trichoderma, Aspergillus, and Penicillum attack cellulose
 Marasmius, Ganoderma, Psalliotta attack lignin
 In less acid , neutral condition .Bacteria degrade cellulose
and hemicellulose
 Actinomycetes also attack lignin.

11. Nitrogen Fixation:
The process of converting N2 into biologically
available nitrogen is called nitrogen fixation.
1. Nitrogenase Enzyme
2. Bacterial activity
3. Microorganisms involved
Four ways to fix atmospheric nitrogen:
1. Biological fixation, 2. Industrial Nitrogen Fixation
3. Combustion 4. Ligtening

12. Biological Nitrogen Fixation
• microorganisms fix 60% nitrogen for requirement of plants
• Two groups of microorganisms are involved in the process of BNF
Non-symbiotic (free living)
1. Aerobic heterotrophs - Azotobacter, Pseudomonas,
Achromobacter
2. Aerobic autotrophs - Nostoc, Anabena, Calothrix, BGA
3. Anaerobic heterotrophs - Clostridium, Kelbsiella.
Desulfovibrio
4. Anaerobic Autotrophs - Chlorobium, Chromnatium,
Rhodospirillum, Meihanobacterium
Symbiotic (Associative)
1. Rhizobium, in legumes

14. Formation of a Root Nodule

15. Role of microorganisms in Nitrogen cycle
Nitrification:
The first step is the oxidation of ammonia to nitrite
carried out by microbes known as ammonia-oxidizers-
Nitrosomonas, Nitrosospira, and Nitrosococcus
The second step in nitrification is the oxidation of
(NO2
-) to (NO3
-)
This step is carried out by nitrite-oxidizing Bacteria,
include Nitrospira, Nitrobacter, Nitrococcus, and
Nitrospina.

16. Denitrification:
NO-
3 => NO-
2 => NO + N2O = > N2
Denitrifying bacteria include
Bacillus, Paracoccus, and Pseudomonas.

19. Role of Microorganisms in Phosphorous
Cycle
 The activity of microorganisms in phosphate
solubilization is influenced by various soil factors such as
pH, moisture, and aeration.
 Many fungi and bacteria (Aspergillus, Penicillum,
Bacillus) are potential solubilizers of bound phosphates.

22. 1. Mineralization
2. Oxidation
3. Reduction
4. Assimilation
Oxidation:
 Oxidation of elemental sulphur and inorganic sulphur
compounds (such as H2S, sulphite and thiosulphate) to
sulphate (SO4) is brought about by chemoautotrophic and
photosynthetic bacteria.
 The major Sulphur Oxidiser microorganisms are:
Thiobacillus, Beggiatoa, Thiothrix, Thioploca,
Aspergillus, Penicillium, Microsporum
Role of microorganisms in sulphur cycle

23. Reduction:
 Sulphate can be reduced to hydrogen sulphide
(H2S ) by sulphate reducing bacteria
(eg.Desulfovibrio and Desulfatomaculum)
 Hydrogen sulphide produced by the reduction of
sulphate and sulphur containing amino acids
decomposition is further oxidized by some
species of green and purple phototrophic
bacteria (eg. Chlorobium, Chromatium) to release
elemental sulphur.

24. BIOFERTILIZER
Carrier base microbial inoculum containing
sufficient cells of efficient strains of specific microorganism
that help in enhancing soil fertility either by fixing atm N,
solubilization or mineralization of nutrient element or
decomposing organic waste by augmenting plant growth
substances with their biological activity.

25. S.NO GROUP EXAMPLE
N2 Fixers
1. Free-living Azotobacter, Beijerinkia, Clostridium, Klebsiella,
Anabaena, Nostoc
2. Symbiotic Rhizobium, Frankia, Anabaena azollae
3. Associative Symbiotic Azospirillum
P Solubilizers
1. Bacteria Bacillus megaterium var. phosphaticum, Bacillus subtilis,
Bacillus circulans, Pseudomonas striata
2. Fungi Penicillium sp, Aspergillus awamori

26. Biofertilizers for Micro nutrients
1.
Silicate and Zinc
solubilizers
Bacillus sp.
Plant Growth Promoting Rhizobacteria
1. Pseudomonas Pseudomonas fluorescens
P Mobilizers
1. Arbuscular mycorrhiza Glomus , Gigaspora , Acaulospora,
Scutellospora
Sclerocystis sp.
2. Ectomycorrhiza Laccaria, Pisolithus, Boletus ,Amanita
3. Ericoid mycorrhizae Pezizella ericae
4. Orchid mycorrhiza Rhizoctonia solani

27. Benefits from biofertilizers
Restore the soil's natural nutrient cycle
Build soil organic matter
Increase crop yield by 20-30%
Replace chemical nitrogen and phosphorus by
25%
Stimulate plant growth
Activate the soil biologically
Restore natural soil fertility
Provide protection against drought and some soil
borne diseases.