Agricultural microbiology

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

6. Nitrogen cycle It is a cyclic process by which nitrogen is converted between its various chemical forms 5 steps are involved in nitrogen cycle 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

7. 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

8. 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 T hiothrix

9. 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

10. Bio fertilizers Bio fertilizers are low cost, renewable source of plant nutrients which supplement chemical fertilizers 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

11. 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 A zolla 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 , C alothrix , Scytonema …… Crop production can be increased by mass production of cyano bacterial bio fertilizers or massive cultivation of A zolla

12. Azollaa Anabaena azollae A ulosira Scytonema

13. 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

14. Bacillus polymyxa Glomeromycota

15. 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

16. 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

17. 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 P ythium ultimum & Fusarium oxysporum Advantage Low cost Environmental safety Absence of development of resistance

18. 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

19. 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

20. 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 S oil 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

21. 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

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