bio geo chemical cycles,bio fertilizer.......

1. AGRICULTURAL
MICROBIOLOGY
SHANID MOOSA M.I.

2. What is agricultural microbiology…?
Agricultural microbiology is a field of study
concerned with plant-associated microbes
It also deals with the microbiology of soil fertility,
such as microbial degradation of organic matter
and soil nutrient transformations

3. BIOGEOCHEMICAL CYCLES
 Microbes play an important role in biogeochemical cycles –
because of their ubiquitous distribution and diverse enzymatic
activities
 Mainly 3 types of biogeochemical cycles
 Carbon cycle
 Nitrogen cycle
 Sulfur cycle

4. Carbon cycle
 Carbon is exchanged among the biosphere, geosphere, hydrosphere and
atmosphere of the earth
 carbon is actively cycled between inorganic Co2 and the variety of organic
compounds that compose living organisms and their dead organic matter
 Among the step of carbon cycle decomposition of organic matter by microbes
is very important
 Decomposition of organic matter in soil is done by fungi along with other
microbes, chiefly bacteria
 Decomposition help to release nutrient blocked up in the dead organic matter
of plants and animals

5.  In soil, microbes oxidize organic carbon into Co2 and liberate bound materials
 Several types of decomposers are present
 Cellulose decomposers – cellulose decomposing fungi mainly include Ascomycetes
and Deuteromycetes
eg. Apergillus, Penicilium, Trichoderma, fusarium etc
They break down cellulose simple sugar
 Lignin decomposers – decomposed by Bascideomycetes such as Aphyllophorales &
Agaricales
decomposition done by the production of lignolytic enzymes
Besides fungi, bacteria are also involved in the decomposition
 Pectin decomposers – pectin substance are breakdown by microbial pectinase
Pectinase are produced by various specious of Rhizopus, Aspergillus, Fusarium and
Geotrichum etc

7. Nitrogen cycle
 It is a cyclic process by which nitrogen is converted between its
various chemical forms
 5 steps are involved in nitrogen cycle
1. Nitrogen fixation – atmospheric nitrogen is converted in to
ammonia or organic compounds
Nitrogen fixation in soil is carried out by symbiotic(Rhizobium)
or free living bacteria(Azotobactor, Azomonas)
In aquatic habitat – Nostoc and Anabaena
2 . Nitrification – in this step ammonium ion initially oxidized in to
nitrite ions, subsequently in to nitrate ions
This process is carried out by nitrifying bacteria such as
Nitrospora, Nitrosococcus and Nitrosolobus

8. 3 .Assimilation – in this step nitrites and nitrates produced in
the whole
nitrogen cycle are consumed by plants and animals
4 . Ammonification – organic nitrogen is converted in to
ammonia
5 .Denitrification – in this step fixed forms of nitrogen is
converted in to
molecular nitrogen
This process is also mediated by microbes
some E.coli are only able to reduce NO3 to NO2
Subsequent conversion can be done by many other
bacteria like, Pseudomonas, Spirillum and Theobacillus etc

10. Sulfur cycle
Sulfur can exist variety of oxidation states within
organic and inorganic compounds
Each oxidation – reduction reaction is mediated
by microbes
Under anaerobic condition H2S is produced from
mineralization of organic sulfur compounds
This H2S is utilized by Beggiatoa and Thiothrix

12. There are many other cycles are present
Microbes also involved in these cycles for
cycling of minerals
Eg. Hydrogon cycle, Oxygen cycle …..
Due to the presence of wide variety of
microbes in soil they help to increase fertility
of soil and there by enhance the agricultural
productivity

13. Bio fertilizers
 Bio fertilizers are low cost, renewable source of plant nutrients which
supplement chemical fertilizers
1) Bacterial fertilizers
Using chemical fertilizers cause both health and pollution problem,
besides these are quite expensive
Bacterial fertilizers are the formulation of living organisms which are able
to fix atmospheric nitrogen in the available form for the plants
Green manuring
It is a farming practice in which Leguminous plants are sown
in to the ploughed soil and remove non leguminous plants
Due to hike in price of chemical fertilizers the practice of green manuring
practice is re emphasized
Eg for some cultivated legumes are Crotalaria striata, Crotalaria juncea

14. Algal and other bio fertilizers
 Biological nitrogen fertilizers play a vital role in solving the
problem of soil fertility
 Anabaena azollae – live in symbiotic association with Azolla
 Anabaena azollae can grow photoautotrophically and fix
atmospheric N2
 Nitrogen fixing bacterias like Anabaena azollae, Anabaena
variabilis when immersed in polyurethane and sugarcane
waste – significantly increase N2 fixing capacity and ammonia
secretion
 Inoculation of cyano bacteria in to rice field increase growth
of rice
 Other N2 fixing bacterias are Aulosira, Calothrix, Scytonema
……
 Crop production can be increased by mass production of

15. Azollaa Anabaena azollae
Aulosira Scytonema

16. Phosphorous aiding bio fertilizers
 Tropical soil are deficient in phosphorous
 Some fungi such as, Aspergillus awamori, Penicillium digitatum etc
and bacteria like Bacillus polymyxa, Pseudomonas striata etc which
can solubilize unavailable form of phosphorous into available
forms
 Vesicular arbuscular mycorrhizal(VAM) fungi colonize in the roots
of several plants
 they are Zygomycetes fungi belongs to the genera Glomus,
Acaulospora
 They are obligate symbionts – cannot be cultured on synthetic
media
 Help plant growth through improved phosphorous nutrition and
protects root against pathogen

17. Bacillus polymyxa Glomeromycota

18. Production of mycorrhizal bio fertilizers
 Ectomycorrhizal fungi
• Basidiospore, chopped sporocarps, sclerotia, pure mycelial culture,
fragmented mycorrhizal root and soil from mycorrhyzosphere can
be used as inoculum
• Inoculum is mixed with nursery soil and seeds are sown
 Endomycorrhizal fungi
• Produced in large scale by pot culture
• Requires host plant mycorrhizal fungi and natural soil
• Host plants – Sudangrass, Strawberry, Maize…..
• Starter inoculum is isolated from soil and inserted in to pot media

19. Bio pesticides
To minimize the use of plant protection chemicals
Microbes are used to protect plant from insect and
nematode pests
Microbial population can be used directly for
controlling plant pests
Preparation of these antagonistic microbial
population – microbial pesticides

20. Microbial insecticides
 Bacterial insecicides
• Several bacterias are used as insecticides
• It include endospore forming Bcillus and Clostrium species
• Non endospore forming –and proteus………Pseudomonas
enterobacter, Xenorhabdus
• Bacillus thuringiensis – most extensively used to control various
pests
• It kill wide range of insect like moths, beetle, mosquito, flies, aphids,
ants, termite and even some pathogenic fungi such as Pythium
ultimum & Fusarium oxysporum
 Advantage
1. Low cost
2. Environmental safety
3. Absence of development of resistance

21. Viral insecticides
• Some pathogenic viruses are used as pesticidal agents
• Virus attack insects and other arthropods
• Specificity of virus host relationship make them ideal for
this purpose
• Nuclear polyhidrosis viruses (NPV), Cytoplasmic
polyhidrosis viruses(CPV),Granulosis viruses(GV)
• These type of viruses do not infect plants, infect only
pests

22. Fungal insecticides
• Most common and effective means of control of
insect pests
• Mainly entamogenous fungi are used
• Different kinds of formulations have been
developed and applied in different ways against
insect pests
• Metarhizium, Verticillium, Hirsutella and
entomophthora

23. Microbial nematicides
 Most studies have been made with fungal nematicides
 Classical nematode trapping fungi belonging to the genera,
Arthrobotrys, Dactylaria, Dactylella and Monocosporium used
agains nematode genera Meloidogyne, Heterodera and
Rotylenchulus
 These nematode cause cyst and root knot disease
 Using of these fungi are difficult
 Soil fungi have been found more ideal nematicides , these are
‘oppertunistic fungi’ such as Verticillium chlamydosporous
Dactylella oviparasitica – attack eggs and young females of cyst and
root knot nematode

24. Microbial herbicides
Fungi should be most suitable for this purpose
Puccinia chondrillina to control rush skeleton
weed in Australia and west US
Phragmidium violaceum to control European
blackberry in Chile
Weed plant is repeatedly inoculated and various
product are use in commercial scale

25. THANK YOU