Biofertilizer 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.


Rhizobium sp. Crops
R.leguminosarum Peas (Pisum), lathyrus, Vicia, Lentil (Lens)
R. trifoli Berseem (Trifolium)
R. phaseoli Kidney bean (Phaseolus)
R. lupini Lupinus
R.japonicum Soybean (Glycine)
R. meliloti Melilotus, Lucerne (Medicago), Fenugreek (Trigonella)
Cowpea miscellany Cowpea, cluster bean, greengram, blackgram, redgram, groundnut, moth bean, dhaincha, sunhemp, Glyricidia, Acacia, Prosophis, Dalbergia, Albizzia, Indigofera, Tephrosia, Atylosia, Stylo
Separate group Bengalgram (gram)

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 oC.

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 oC.

• 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 awamorii 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.

• Gross quantity of crop residues annually available in India is 686 million tonnes.

• Crop – residue to economic yield ratio

Rice – 1.4

Wheat – 1.3

Maize – 2.0

Barley – 1.5

• Out of the total residue produced in India, cereal crops contribute the highest amount followed by sugarcane.

• The silica content in rice straw is 12-16% and wheat straw is 35%.

• Wheat straw contains approximately 0.53% N.

C:N ratio of wheat straw is more than rice straw.

• The rice straw contains 50-100% higher concentration of K than in wheat straw.

• Machines used for zero-till planting of crops under surface residue conditions is turbo happy seeder, rotary disc drill and double disc drill.

Hydraulic conductivity and infiltration rate are higher in no-till with residue retention compared to conventional till with residue incorporation.

Gas – Qty released by burning 1 tonne of rice residue

CO2 – 1515 kg

CO – 92 kg

NOx – 3.83 kg

CH4- 2.7 kg

Non-methane volatile organic compounds – 15.7 kg

SO2 – 0.4 kg

Nutrient – Content in 1 tonne rice straw

N – 5-8 kg

P – 0.7 -1.2 kg

K – 15-25 kg

S– 0.5 -1 kg

Ca – 3-4 kg

• Cellulose content in crop residues on dryweight basis is 15-60%.



Protein 2-15%

• The potential of no-till can be fully realized only when it is practiced continuously and the soil surface is covered at least 30% by crop residues or other organic materials.

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