In nature, there are a number of useful soil micro organisms which can help plants to absorb nutrients. Their utility can be enhanced with human intervention by selecting efficient organisms, culturing them and adding them to soils directly or through seeds. The cultured micro organisms packed in some carrier material for easy application in the field are called bio-fertilisers. Thus, the critical input in Biofertilisers is the micro organisms.
Benefits of biofertilizers
Bio-fertilisers are living microorganisms of bacterial, fungal and algal origin. Their mode of action differs and can be applied alone or in combination.
- Biofertilizers fix atmospheric nitrogen in the soil and root nodules of legume crops and make it available to the plant.
- They solubilise the insoluble forms of phosphates like tricalcium, iron and aluminium phosphates into available forms.
- They scavenge phosphate from soil layers.
- They produce hormones and anti metabolites which promote root growth.
- They decompose organic matter and help in mineralization in soil.
- When applied to seed or soil, biofertilizers increase the availability of nutrients and improve the yield by 10 to 25% without adversely affecting the soil and environment.
List of commonly produced bio-fertilizers in India
Name Crops suited Benefits usually seen Remarks
|Rhyzobium strains||Legumes like pulses, groundnut, soybean||10-35% yield increase, 50-200 kg N/ha.||Fodders give better results. Leaves residual N in the soil.|
|Azotobacter||Soil treatment for non- legume crops including dry land crops||10-15% yield increase- adds 20-25 kg N/ha||Also controls certain diseases.|
|Azospirillum||Non-legumes like maize, barley, oats, sorghum, millet, Sugarcane, rice etc||10-20% yield increase||Fodders give higher/enriches fodder response. Produces growth promoting substances. It can be applied to legumes as co-inoculant|
|Phosphate Solubilizers (there are 2 bacterial and 2 fungal species in this group)||Soil application for all crops ||5-30% yield increase ||Can be mixed with rock phosphate.|
|Blue-green algae and Azolla||Rice/wet lands||20 -30 kg N/ha, Azolla can give biomass up to 40-50 tonnes and fix 30-100 kg N/ha||Reduces soil alkalinity, can be used for fishes as feed. They have growth promoting hormonal effects. |
|Microhizae (VAM)||Many trees, some crops, and some ornamental plants||30-50% yield increase , enhances uptake of P. Zn, S and Water.||Usually inoculated to seedlings.|
Biofertilizers recommended for crops
- Rhizobium + Phosphotika at 200 gm each per 10 kg of seed as seed treatment are recommended for pulses such as pigeonpea, green gram, black gram, cowpea etc, groundnut and soybean.
- Azotobacter + Phosphotika at 200 gm each per 10 kg of seed as seed treatment are useful for wheat, sorghum, maize, cotton, mustard etc.
- For transplanted rice, the recommendation is to dip the roots of seedlings for 8 to 10 hours in a solution of Azospirillum + Phosphotika at 5 kg each per ha.
Application of biofertilizers to crops
- Seed treatment: 200 g of nitrogenous biofertilizer and 200 g of Phosphotika are suspended in 300-400 ml of water and mixed thoroughly. Ten kg seeds are treated with this paste and dried in shade. The treated seeds have to be sown as soon as possible.
- Seedling root dip: For rice crop, a bed is made in the field and filled with water. Recommended biofertilizers are mixed in this water and the roots of seedlings are dipped for 8-10 hrs.
- Soil treatment: 4 kg each of the recommended biofertilizers are mixed in 200 kg of compost and kept overnight. This mixture is incorporated in the soil at the time of sowing or planting.
Tips to get good response to biofertilizer application
- Biofertilizer product must contain good effective strain in appropriate population and should be free from contaminating microorganisms.
- Select right combination of biofertilizers and use before expiry date.
- Use suggested method of application and apply at appropriate time as per the information provided on the label.
- For seed treatment adequate adhesive should be used for better results.
- For problematic soils use corrective methods like lime or gypsum pelleting of seeds or correction of soil pH by use of lime.
- Ensure the supply of phosphorus and other nutrients.
Precautions to take while using biofertilizers
- Biofertilizer packets need to be stored in cool and dry place away from direct sunlight and heat.
- Right combinations of biofertilizers have to be used.
- As Rhizobium is crop specific, one should use for the specified crop only.
- Other chemicals should not be mixed with the biofertilizers.
- While purchasing one should ensure that each packet is provided with necessary information like name of the product, name of the crop for which intended, name and address of the manufacturer, date of manufacture, date of expiry, batch number and instructions for use.
- The packet has to be used before its expiry, only for the specified crop and by the recommended method of application.
- Biofertilizers are live product and require care in the storage
- Both nitrogenous and phosphatic biofertilizers are to be used to get the best results.
- It is important to use biofertilizers along with chemical fertilizers and organic manures. Biofertilizers are not replacement of fertilizers but can supplement plant nutrient requirements.
- TNAU Agritech portal
- NABARD Knowledge bank