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7. Microbes as Biofertilisers, are the microorganisms which enrich the nutrient (nitrogen, phosphorus, etc.) quality, Biofertilisers, of the soil., Bacteria, fungi and cyanobacteria are the three main sources of biofertilisers., , () Bacteria as biofertilisers, Rhizobiu is a symbiotic bacterium that lives in the root nodules of legumes and fixes atmospheric, , Azospirilhum and Azotobacter are free-living bacteria which absorb free nitrogen, , from soil, air, , and convert it into salts of nitrogen and enrich soil nutrients., , (ii) Fungi as biofertilisers, form syrmbiotic association with the roots of higher plants called mycorrhiza, eg, Glomus., Fungi, The fungal hyphae absorb phosphorus from soil and passes it to the plant., shows the tollowing benetits to plant:, Mycorrhiza, ) resistance to root-borne pathogens., (6) tolerance to salinity and drought., c) overall increase in plant growth and development, , (iii) Cyanobacteria, , as biofertilisers, , fix atrmospheric nitrogen and increase the organic matter of the soil through their, They, photosynthetic activity, es, Nostox, Anabuena, Ontillatorin, etc., Blue-green algae increase the soil fertility by adding organic matter to the soil., , Cyanobacteria are important biofertilisers in paddy fields., Advantages of biofertilisers, () Increase fertility of soil., (6) Reduce dependency on chemical fertilizers., , Microbes, , in, , Human Welfare, , 369

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6. Microbes, , as Biocontrol, , Agents, , is defined as controlling plant diseases and pests using biological methods., Biocontrol, chemicals like insecticides and pesticides were used for biocontrol., Earlier,, of chemical agents:, Disadvantages, () Chemicals are toxic and harmful to human beings and animals., and plans, (u) Chemicals pollute the environment, in) Weedicides used to remove weeds also pollute the soi., , farmers use a holistic approach for following reasons:, ) Keeping pests at manageable levels by a complex system of checks and balances, within, exOsystem, instead ot their complete eradication., (i) Complete eradication of pests is undesirable, as without them the beneficial predatory parasitic insects which depend on them as food or act as host will not be survive. This, disturb the balance of the ecosystem., , Organic, , 368 Xam idea Eulany-X, , (ii) Biocontrol agents reduce dependency on toxic chemicals and fertilizers, are some of the approaches for biological farming, Following, Familiarity, (), with various life-forms inhabiting the fiekd., (i) Gain knowedge about the life cycls, patterns of feeding and habitat of predators and pest, , Some Examples of Biocontrol, Ladybirds and Dragontlies are used to get rid of apthids and mosquitoes respectively., (6) The bacteris Banrtlus thuringiensis (Bt) are uved to control buttertily caterpillars., Dried sypores ot Bt are mixed with water and sprayed on plants such as brassicas and fruit tr, Inseet larvae, after eating these are killed by the toxin reeased in their gut., B. thuringiensis toxin genes have been introduced into plants to provide resistance to pests., to), , ), , Pxample, Bt cotton,, Trahalerma sps, free-living fungi, are presernt in root ecosy'stems where they act against seve, , plant pathogens., (d) Baculoviruses are pathogens that attack inserts and other arthropods., Most of these bicKontrol agents belong to the genus Nuclapolyhrdrvvirus. These are sper, Specitic, narrow spectrum insecticides., They do not harm plans, mammals, birds, fish and other non-target insects, Bacukoviruses are helpful in integrated pest management (1PM) programme, in wh, beneficial insects are conserved and there is no negative impact on plant mammals, birds,, or nontarget insects

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(V) asy, , DIFFERENCES BETWEEN MANURE AND BrOFERTILIZERS, , Manure, , midecaved organic substance of biological, , ., , Biofertilizer, Itis an organism which increas es nutrients avail-, , ability to crop plants., aerastructure,, 2 These are not essential for maintaining soil struc, mnaintaining soil, Itis essential for, ture, aeration and hydration., soil., tion and hydration of, 3. It provides one or few nutrients to crop plants., to crop plants., It provides all types of nutrients, of the4. It can meet all the nutritional requirement of crop, It cannot meet the nutritional requirement, 'plants., plants., origin., , 2, , 3., 4., , Crop, , BIOPESTICIDES, grasses, mites, nematodes, rats etc., Chemical compounds which are used to kill harmful insects, germs,, variously. Today a large number of pesticides are, like organisms. These living beings harms human beings, or synthetic pesticides whereas, available in the market. The pesticides of chemical origin are called chemical, biopesticides., organisms which are used to kill or control harmful organisms are called, Biopesticides are oftwo types, (weeds) growing along, which are used to destroy unwanted plants, Biopesticides, Bioherbicides:, 1., selectively eat specifc varieties of, with crop plants are called bioherbicides. It includes same insects that, of, been checked by the introduction, pliants. e.g. In India and Australia, the excessive growth of cacti has, developed in 1981. It is based on tne, cOchineal insect (Cacloblasis cactorum). The first bioherbicide was, citrus, growth of milk weed vines in, plamivora and is a mycoherbicidal. It controls the, , yophthora, orchards., , nsecticide:, , to kill aphids., , Biopesticides that kills insects are called, , bioinsecticides. e.g. Use of praying, , manus, , aaticides are pbtained, , from