• Microrganism – Function
Rhizobium spp. – Nodulation and nitrogen fixation
Arbuscular Mycorrhizae – Nutrient mobilization
Phanerochaete chrysosporium – Composting
Azolla – Improve nitrogen availability in rice
Bacillus megaterium – Silicate/Phosphate solubilization
• Biofertilizers can be applied as seed coating, soil application or seedling dip.
• Dry formulations of microbial inoculants can be in the form of dusts, wettable powders, granules, pellets, capsules and briquettes.
• Commonly used carriers for biofertilizers are peat, lignite, soil, charcoal, vermiculite, talc, vermicompost, sawdust and pressmud.
• Biofertilizer – specific crop Azospirillum – Cereals, particularly grasses Blue green algae – Rice Frankia – Casuarina Azotobacter – cotton
• Frankia fixes nitrogen.
• Rhizobium establishes efficient symbiotic associations with pulses, leguminous oil-seeds and fodder crops.
• For seed treatment, Rhizobium inoculum @ 1.5kg/ha is mixed in the jaggery solution and sprinkled over the seeds.
• Free living organisms that can fix atmospheric nitrogen are blue green algae (BGA), Azolla, Azotobacter and Rhizospirillum.
• BGA and Azolla can survive only in lowland conditions.
• Important species of BGA that fix atmospheric nitrogen are Anabaena and Nostoc.
• Amount of nitrogen fixed by BGA ranges from 15-45 kg N/ha.
• BGA can grow at a temperature of 25 to 45 °C.
• Bright sunshine increases the growth rate of BGA while rains and cloudiness slows growth rate.
• BGA grows well in a pH range of 7 to 8 and in soils with high organic matter.
• BGA inoculum is applied after transplantation of rice crop in the main field.
• Amount of BGA inoculums required is 10 kg/ha.
• Azolla is a free-floating water fern which forms symbiotic association with blue-green algae species Anabaena azollae present in the lobes of Azolla leaves and provides nitrogen to rice crop.
• Azolla pinnata is the most common species occurring in India.
• A thick mat of Azolla supplies 30-40 kg N/ha.
• Unlike blue-green algae, azolla thrives well at low temperature.
• Normal growth of Azolla occurs in the temperature range of 20 to 30 °C .
• Azolla grows better under monsoon season with frequent rains and cloudiness.
• For Azolla suitable soil pH is 5.5-7.0.
• Amount of Azolla inoculum required is 0.1 to 0.5 kg/m2.
• As green manure crop, Azolla is allowed to grow on the flooded fields for 2 to 3 weeks before transplanting, later water is drained and Azolla is incorporated by ploughing in.
• Advantages of Azotobacter to crops are Biological nitrogen fixation, release of growth promoting substances, suppression of plant diseases.
• Azotobacter chroococcum is capable of fixing 20 to 30 kg N/ha.
• Amount of Azotobacter inoculums required is 3-5 kg/ha.
• Azotobacter can be used for rice, cotton and sugarcane.
• Acetobacter is commercially utilized for Sugarcane.
• Azospirillum inoculants are recommended in several crops such as jowar, bajra, ragi and other millets.
• Cell number or colony forming units at the time of manufacture should not be less than 108 and 107 per gram of carrier material, respectively for Rhizobium and Azotobacter.
• Pseudomonas striata, Aspergillus awamori and Bacillus polymyxa are capable of solubilising phosphates.
• Liquid inoculants and biofilmed inoculants are new generation biofertilizers.
• Shelf life of liquid biofertilizers is 12-24 months.
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