As per the Fertiliser Control Order (FCO), 1985, ‘biofertiliser’ is any product containing carrier based (solid or liquid) living microorganisms, which are agriculturally useful in terms of nitrogen fixation, phosphorous solubilisation or nutrient mobilisation, increasing the productivity of the soil and crop. Biofertilisers are also known as bioinoculant or microbial inoculant or cultures. On application, the microorganisms (bacteria, fungi, actinomycetes, algae alone or in combination), help in fixing nitrogen, solubilising phosphorus etc., in addition to secreting growth promoting substances.
Biofertiliser was developed with the discovery ( H Hellriegel and H Wilfarth) of biological nitrogen fixation by legumes during 1886-88. Historically, the use of chemical fertiliser in agriculture was initiated in 1830-1840 by the utilisation of Chilean nitrate deposits. Thus experiments on both fertiliser and biofertiliser started about the same time—during the mid nineteenth century. Globally, the commercial history of biofertiliser began with the launch of the rhizobium ‘Nitragin’ by F Nobbe and L Hiltner in 1896. Consequently azotobacter (1902), azospirillum(1925), blue-green algae (1939), and phosphate solubilising biofertiliser (1956) were used on a commercial scale during the last phase of 20th century. Use of mycorrhizae as biofertiliser is recent development. First commercial production of rhizobium biofertiliser in India began in 1956 and by late 1960’s when soybean was introduced, large scale production began.
Classification and type
Biofertilisers are classified into four categories:
Nitrogen biofertiliser (N-BF)
■ Rhizobium – symbiotic BF with all legumes.
■ Azotobacter – non-symbiotic BF for cereals, vegetables, horticulutral crops.
■ Azospirillum – associative BF for millets, maize etc. (blue-green algae, azolla, gluconoacetobacter diazotrophicus are also N-BF, but is yet to be included in FCO)
Phosphorus biofertilisers (P-BF)
■ P-solubilisers – PSB (bacillus, pseudomonas etc, for all crops)
■ P-mobilisers – mycorrhizae (glomus, gigaspora etc. for all crops)
Potash biofertilisers – K-BF (microbes like B.mucilogenosus and F.aurantia for all crops).
Zinc solubilisers – Z- BF (Bacillus microbes are capable of zinc solubilisation).
Generally biofertilisers are available in a solid (using peat, lignite, charcoal etc. as a carrier), or in a liquid base (using broth involving additives like poly vinyl pyrolidon, gum, biosurfactants etc. or by promoting dormant cells/spores). Biofertilisers may be prepared from either single or multiple strains and experiments are also being conducted for formulating freeze dried, granular and polyacrylamide entrapped inoculant. At present, however, best production technology and packaging are yet to be obtained.
The microorganisms present in biofertilisers are available in nature. Initially, these organisms are isolated from different sources such as the root nodule for rhizobium; soil for other microbes; etc., and developed in specific media. For example yeast extract manitol media is used for rhizobium, Jensen media is used for azotobacter, Dobernier media is used for azospirillum, etc. After needful growth these organisms are multiplied in liquid broth either in rotary shaker or in a fermentor. When organisms attain maximum population (108/109 per ml ) the broth containing specific microbe are mixed with the carrier.
Biofertilisers can be applied in several ways. The first, seed treatment, is most common. The process includes preparation of paste or slurry by mixing 200g of biofertilisers with 400 ml water and pouring it on 10-15 kg seeds. Then the inoculated seeds are spread in shade for 10-15 minutes for drying after which they are sown immediately. The second technique, soil application, is by broadcasting the biofertiliser on or before sowing. The method includes preparation of 5-7 kg mixture of biofertiliser in 100-150 kg soil/compost and broadcasting the mixture over an acre (0.4 ha) of land.
The third technique involves seedling inoculation which includes preparation of a suspension of 1-2 kg of biofertilisers in 10-15 litres of water, then dipping the seedlings (obtained from 10-15 kg of seeds ) into the suspension for 20-30 minutes and transplanting the treated seedlings immediately.
Impact of Biofertilisers
The use of biofertilisers improves soil fertility status by increasing the organic matter, microbial biomass, and available nutrient status, particularly that of nitrogen and phosphorous. Under a central sector scheme (1983-2004) National Project on Development and Use of BioFertilisers (NPDB) 1050 field demonstrations were conducted on 53 crops in 25 states/union territories. The results of these trials show that biofertiliser application resulted in an increase of 11.4 per cent in crop yield on an average.
Status of Biofertiliser in India
During 1990, the production of biofertiliser in India was 1000 tonnes, primarily for rhizobium. But during (2009-10), the total biofertiliser production reached 20,090 tonnes with PSB dominating the scene (Bhattacharyya P. et al., 2012, ‘Biofertiliser Handbook-research-production-application’, Fertiliser Development & Consultation Organisation) (Table 1). The estimated production for 2010-11 is 38,000 tonnes (Table 2). It has been also estimated that from 2002-03, when the average consumption of biofertiliser for the country was 64g/ha, it has today risen to nearly 90-100g/ha. It was also observed that the maximum capacity utilisation of biofertiliser is in the south zone at 88 per cent, while the east zone mapped the lowest capacity utilisation at about 33 per cent (ibid.).
Initially, commercial production of biofertilisers was started in a few agricultural research institutes, agricultural universities, state agricultural departments and in the fertiliser cooperative sectors. Later, private fertiliser companies and non-governmental organisations were also involved in commercial production. At present, there are more than 150 biofertiliser companies engaged in production and sale of various products.
The channel of biofertiliser distribution in the Indian market consists of private, cooperatives, government institutions, wholesalers to retailers, dealers and distributors, agro industries, fertiliser companies etc., who primarily depend on ‘push sale’ rather than ‘pull sale’. Retail prices at which biofertilisers are sold generally range from Rs 40 to Rs 100/kg in case of carrier based products and from Rs 150 to Rs 400/litre for liquid biofertiliser.
Earlier, financial and technical assistance to different production units were provided under NPDB. Now the same scheme has been subsumed under National Project on Organic Farming (NPOF) and there is a provision for providing financial assistance for its production and promotion. Besides, there are other schemes such as the National Food Security Mission, Rashtriya Krishi Vikash Yojana, National Horticultural Mission which support and promote this input. Despite being reliable, eco friendly and sustainable, biofertilisers have not been accepted on a large scale by farmers. Some of the constraints are:
■ Biofertilisers do not show instant and dramatic response like the chemical fertilisers.
■ Poor quality of biofertilisers in many cases, has eroded the trust of the farmers. In fact under NPOF, 983 biofertiliser samples were tested in 2009 and 35.6 per cent were found to be sub-standard.
■ Lack of awareness among farmers about proper usage reduce its uptake.
■ Problems associated with shelf life and storage particularly during hot weather result in low efficacy. In fact, several abiotic (pH, temperature, acidity/alkalinity/salinity etc.) and biotic (competition with native strains, incompatibility with other microbes etc.) may influence the efficiency of biofertilisers.
■ Lack of timely supply of inoculants.
■ No advance placement on supply of biofertiliser by state agricultural departments indented under the different schemes.
Microbes in the soil live, grow, perform specialised functions and die. In fact, the availability of nutrients depends mainly on soil-based microorganisms which are involved in nutrient transformation. Apart from N-fixer, P-solubiliser/mobiliser, K-solubiliser, there are several organisms that are involved in the transformation of sulphur, calcium, iron, manganese, zinc, molybdenum etc. Even the efficiency of urea, the most acceptable chemical N-fertiliser depends on the role of microbes that produce urease enzyme to convert it into ammonium salt which the plant readily absorbs. More importantly, the product should bear a quality standard under a strict regulatory mechanism. As the component of integrated nutrient management and newly inducted in the Fertiliser Control Order, it can supplement chemical fertilisers significantly. With further progress of the biofertiliser industry, we may hope that farmers will begin to rely on it as means to prosperity.