Introduction Bio fertilizers are microbial products containing living cells of different types of micro organisms possess the innate ability either to fix or mobilize important nutrient elements from non-usable forms through biological process. needed to be applied to soil to enhance microbial activity in the rhizosphere playing a significant role in intigrated plant nutrient systems (IPNS) Types of Bio Fertilizers Nitrogen fixers Phosphate solubilisers Nitrogen fixers Among N-fixers azospirillum is widely recommended because of its easy adaptability and limited host specificity. A micro aerophilic bacterium Associative symbiotic Lives inside the cortical cells and xylem vessels of plant roots. Also known to secrete growth promoting substances like gibberellic acid and IAA which enhance root proliferation and growth of crop plants. Having ability to fix 25-40 kg N/ha/year. Phosphate solubilisers Phosphorus in soil is in insoluble form due to fixation. In this context the release of soluble phosphorus from fixed and insoluble forms in the soil aided by micro organisms assumes significance. Belonging to the genera bacillus and pseudomonas. Posses the ability to solubilize insoluble forms of phosphorus and make it available to plants. Solubilization affected by the secretion of organic acids and enzymes which facilitate the crop to assimilate phosphorus easily. Known to produce amino acids and growth promoting substances which help in better growth of plants. Solublize and made available about 30 kg P/ha/annum. Applications

Biofertilizers	Function/ Contribution	Limitation	Recommended Dose / ha
AZATOBACTER (Non-symbiotic)	20 – 25 kg N / ha	Demands high organic matter	2 kg / ha
AZOSPIRILLUM (Associative)	10 – 15 % increase yield. Production of growth promoting substance	No limitation	2 kg /ha
BLUEGREEN ALGAEor CYANOBACTERIA (Phototropic)	20 – 30 kg N /ha 10 – 15 % increase in yield. Production of growth promoting substance	Effective only in submergence rice and demands bright sunshine	10 – 15 kg/ha
AZOLLA (Symbiotic)	30 – 100 kg N/ha , Yield increases 20 – 25 %	Survival difficult at high temperatures, great demand for phosphorus and used in flooded rice	10 tons/ha
PHOSPHO BACTERIA	Contributes to solubility of tricalcium, aluminum and iron phosphates making the phosphorus present in the soil available to plants.		2 kg/ha

Soil Application Mix Azospirillum and phosphobacteria required for 1 ha (2 kg each) and add this mixture to 10 lit of water. Sprinkle the suspension on 100 kg FYM and mix uniformly. Apply the mixture near the root zone along the planting rows and cover with soil. Azospirillum and phosphobacteria each at 2 kg/ha are to be mixed with 50 kg of well powdered decomposed FYM/compost. Apply the mixture of biofertilizers to the rice before transplanting. Seed Treatment Prepare a slurry of Azospirillum 600 g +phosphobacteria 600 g with one litre rice gruel and mixed with 25 kg of rice seeds and ensure uniform seed coating. Dry in shade and sow the seeds within an hour of treatment. Advantages of Biofertilizers harnesses atmospheric nitrogen and makes it available directly to the plants. increases phosphorus uptake by solubilising and releasing unavailable phosphorus. enhances root proliferation due to release of growth promoting harmones. increases the crop yields by 10 – 25 %. improves soil properties and sustain soil fertility. are cost effective and environment friendly. benefit to cost ratio of biofertilizers is fairly high. Precautions to be Taken While applying Biofertilizers Do not mix biofertilizers with fertilizers, insecticide and herbicides. Treat the seed with bio fertilizer with a gap of 24 hrs if seeds are to be treated with other types of dressing chemicals(fungicides, herbicides etc.,) Store biofertilizer packets away from sunlight or heat. Use biofertilizer before the expiry date indicated on the packet. Irrigation has to be given after biofertilizer application.

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