About biofertilizers: Biofertilizers or bioinoculants are formulations of living microorganisms, particularly plant growth promoting rhizobacteria (PGPR) which are used similarly like chemical fertilizers to promote plant growth and increase the yield. Biofertilizers are classified as Nitrogenous, Phosphatic and Organic matter decomposers depending upon role they perform. Thus rhizobacteria which have potential to fix atmospheric nitrogen or produce plant growth hormones like IAA, ethylene, gibberellin or their derivatives or to solubilize inorganic phosphatic compounds or mobilize inactive forms of copper, manganese, sulfur or calcium into plant utilizable form constitute the biofertilizers. These biofertilizers are being used by farmers since old time when the role of microbes in plant growth promotion was unknown. They have been used with excellent growth and yield results for various types of plants such as Cereals (Rice, wheat etc), Pulses (Pea, green gram, black gram etc), Oil seeds (Soybean, groundnut etc), Vegetables (Tomato, Lady finger etc), Fodder crops (Acacia, Sorghum etc), Fruits plants (Melon, papaya, etc), Cash crops (Sugarcane, tobacco), Ornamental and flowering Plants (Roses, bougainvillea, etc), Spices (Pepper, clover etc) and forest trees (Pine, oak etc). Biofertilizers of Azotobacter, Azospirillum and Rhizobium are most popular in the farmers. Plant growth promoting fungi like Penicillium, Trichoderma, Aspergillus and Paecelomyces have also been commercialized as biofertilizers. Actinomycete like Frankia is specifically used for biofertilization of forest trees. Blue green algal fertilizers from Nostoc, Anabaena and Azolla are principally used for paddy cultivation. Rhizobacteria having biocontrol properties like Pseudomonas, Bacillus and Trichoderma have been formulated as biofertilizer biopesticides.
Misconceptions: Adverse effects of chemical fertilizers are well known but are still preferred by farmers for crops. This is because they are not aware of usefulness of biofertilizers or have misconceptions regarding biological material. The farmers particularly from the developing countries think that biofertilizers are something 'dirty/ or danger to handle or not effective like chemical fertilizers.' Biofertilizers have also not effectively been marketed.
Why to apply: Biofertilizers are renewable and ecofriendly; maintain healthy native soil microflora and nutrient status. Their production cost is very low; have commercially acceptable shelf life and potency. On the contrary, chemical fertilizers demand high cost of production and they are toxic if used irrationally. Their constant used has changed soil nutrient composition and have also turned agricultural lands into unfertile grounds. They have displaced and destroyed natural beneficial microorganisms in soil and functioning of geochemical cycles. This has resulted in additional demand of land fertilization, increased susceptibility to diseases, decreased nodulation and healthy plant-microbe interactions in rhizosphere. Considering the detrimental side effects of chemical fertilizers, farmers worldwide should wisely opt for use of biofertilizers.
Method of preparation: In laboratory, bioinoculum is prepared in suitable carrier like lignite powder (mesh size 50-100ï) as a semisolid preparation. Before inoculum preparation, the carrier is autoclaved at 15lbs pressure and 1210C for 1h and cooled. Its pH is adjusted by 10% CaCO3 to 7.3 before addition of inoculum. Bioinoculum is added to trays containing sterile lignite powder under aseptic conditions. It is kept for half an hour at room temperature. Rate of inoculation is determined by counting viable count of culture and maintained throughout the preparation. Bioinoculum so prepared is filled in sterile plastic bags and incubated for 24h. The culture growth in inoculum is monitored at the interval of 30, 60, 90,120,150,180 and 210 days of storage by spread plate method. The shelf life and viability of culture in the inoculum is finally estimated. Bioinoculum so prepared is ready for packaging and sell provided its biofertilization effect on crop/s is predetermined.
Methods of application: There are four ways for application of solid biofertilizer. The most extensively used method is the Seed treatment. The biofertilizer is applied at the rate of 100gm per 5Kg of seeds. The per acre application rate is determined from the amount of seed to be sown in a field. Before the application, biofertilizer is mixed in water (1:2) to form slurry. The slurry is poured in container with seeds to be sown. The combination is mixed properly such that each seed is coated by biofertilizer. The seeds are dried under the shade and then sown. This method is recommended for pulses, oilseeds and fodder crops. The second method is Seedling treatment. Dosewise diluted formulation is required for seedling treatment. About 1 part of biofertilizer in 10 parts of water is prepared. The roots of seedlings to be transplanted in field are dipped in biofertilizer solution for 30 minutes. After the treatment, the seedlings are immediately planted in field without drying. This method is recommended for crops like tomato, brinjal, potato, cabbage, onion, paddy and chilly which are replanted at seedling stage. It is also used for the treatment of ornamental bushes like rose, jasmine, dahlia, marigold and chrysanthemum. The third method of choice is the Set treatment. For this treatment the ratio of biofertilizer to water is 1:50. The explants or cut pieces of planting material are immersed in biofertilizer mixture for 30 minutes. The treated pieces are dried in shade and then planted in field. The crops like sugarcane, banana, grapes and strawberries are recommended to be treated by Set treatment. Biofertilizers can also used for intermittent application for the standing crop or soil treatment before plantation or sowing. For such direct soil applications, biofertilizer is mixed with carriers like soil, compost, farmyard manure, rice husks or lignite (1kg per 25kg of carrier) and then directly put in the soil. The applied area needs to be irrigated immediately. The liquid biofertilizers are applied by spraying or by fertigation. Spraying is recommended for standing citrus plants, vines, mango, guava, custard apple, apple and peach orchards. In fertigation, biofertilizer is mixed in water and other micronutrients in a tank. It is reached to individual plant via irrigation sprinklers or sprayers or piping. This method is usually employed in shade nets and green houses.
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