Bio-Fertilizers Point Wise Notes For Competitive Exam

• 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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