Biofertilizer

India is the second most populous country in the world. With the increasing population, the cultivable land resource is shrinking day to day. To meet the food, fiber, fuel, fodder and other needs of the growing population, the productivity of agricultural land and soil health needs to be improved. Green Revolution in the post independence era has shown path to developing countries for self-sufficiency in food but sustaining agricultural production against the finite natural resource base demands has shifted from the “resource degrading” chemical agriculture to a “resource protective” biological or organic agriculture. Green revolution technologies such as greater use of synthetic agrochemicals like fertilizers and pesticides, adoption of nutrient-responsive, highyielding varieties of crops, greater exploitation of irrigation potentials etc. has boosted the production output in most cases. However, continuous use of these high energy inputs indiscriminately now leads to decline in production and productivity of various crops as well as deterioration of soil health and environments. The most unfortunate impact of Green Revolution Technologies on Indian Agriculture is as follows: 1. Imbalance in production 2. Dependency on synthetic chemical fertilizers 3. Increase in secondary & micronutrient deficiencies 4. Increase in pesticide use 5. Unscientific water management and distribution 6. Reduction in productivity 7. Reduction in quality of the produce 8. Extinction of gene pool 9. Environmental pollution 10. Imbalance in social and economic status All these problems of GRT lead to not only reduction in productivity but also deterioration of soil health as well as natural ecosystem. Moreover, to day the rural economy is now facing a challenge of over dependence on outside inputs and day-by-day increase in price of these inputs. Further, Indian Agriculture will face the market competition due to globalization of trade as per World Trade Organization (WTO). Thus, apart from quantity, quality will be the important factor. Such varieties of concern and problems of modern Indian Agriculture gave birth to various new concepts of farming

such as organic farming, natural farming, biodynamic agriculture, do-nothing agriculture, eco-farming, etc. The essential concept of these practices remains the same, i.e., back to nature, where the philosophy is to feed the soil rather than the crops to maintain soil health and it is a means of giving back to the nature what has been taken from it (Funtilana, 1990). Therefore, for sustaining the productivity of the crop, maintaining the soil health and healthy ecosystem, there is need for adoption of an alternative farming system, may be the organic farming. In most of the developing countries use of chemical fertilizers to increase the crop production is becoming highly essential. Biologically fixed nitrogen is such a source which can supply an adequate amount of nitrogen to the plants and other nutrients to some extent. It is a non hazardous way of increasing soil fertility. Biologically fixed Nitrogen consumes about 25 to 30% less energy than normally used in chemical process. Concentrations of elements in biofertilizers are within the tolerable range. As these plants multiplying rapidly, biofertilizers are required in less quantity. They are also adding some enzymes and growth promoting hormones in the soil. Dead and decaying organic matters increase the humus content of the soil. Hence biofertilizers are more beneficial than inorganic fertilizers. The term ‘biofertilizers’ include selective microorganisms like fungi, bacteria and algae which are capable of fixing atmospheric nitrogen or convert insoluble phosphate in the soil into forms available to plants. Biofertilizers are cost effective, eco-friendly and renewable sources of plant nutrients to supplement chemical fertilizers. Biofertilizers also play a vital role in maintaining long term soil fertility and sustainability. In the strictest sense real biofertilizers are the green manures and organics, materials of biological origin which are added to deliver the nutrients contained in them. Today, Rhizobium and Blue green algae can be considered as established biofertilizers along with Azolla, Azospirillum, Azatobacter, and

Rhizobium. The established biofertilizers should be

referred to as inoculants after the name of microorganisms they contain (Verma and Bhattacharya, 1994). Biofertilizers, more commonly known as microbial inoculants, are artificially multiplied cultures of certain soil organisms that can improve soil fertility and crop productivity. Although the beneficial effects of legumes in improving soil fertility was known since ancient times and their role in biological nitrogen fixation was

discovered more than a century ago, commercial exploitation of such biological processes is of recent interest and practice. The commercial history of biofertilizers began with the launch of ‘Nitragin’ by Nobbe and Hiltner, a laboratory culture of Rhizobia in 1895, followed by the discovery of Azotobacter and then the blue green algae and a host of other micro-organisms. Azospirillum and Vesicular-Arbuscular Micorrhizae (VAM) are fairly recent discoveries. In India the first study on legume Rhizobium symbiosis was conducted by N.V.Joshi and the first commercial production started as early as 1956. However the Ministry of Agriculture under the Ninth Plan initiated the real effort to popularize and promote the input with the setting up of the National Project on Development and Use of Biofertilizers (NPDB). Commonly explored biofertilizers in India are mentioned below along with some salient features. Rhizobium (RHZ): These inoculants are known for their ability to fix atmospheric nitrogen in symbiotic association with plants forming nodules in roots (stem nodules in sesabaniamrostrata). RHZ are however limited by their specificity and only certain legumes are benefited from this symbiosis. Azotobacter (AZT): This has been found beneficial to a wide array of crops covering cereals, millets, vegetables, cotton and sugarcane. It is free living and non-symbiotic nitrogen fixing organism that also produces certain substances good for the growth of plants and antibodies that suppress many root pathogens. Azospirillum (AZS): This is also a nitrogen-fixing micro organism beneficial for nonleguminous plants. Like AZT, the benefits transcend nitrogen enrichment through production of growth promoting substances. Blue green Algae (BGA) and Azolla: BGA are photosynthetic nitrogen fixers and are free living. They are found in abundance in India i. They too add growth-promoting substances including vitamin B12, improve the soil’s aeration and water holding capacity and add to bio mass when decomposed after life cycle. Azolla is an aquatic fern found in small and shallow water bodies and in rice fields. It has symbiotic relation with BGA and can help rice or other crops through dual cropping or green manuring of soil. Phosphate solubilizing (PSB)/Mobilizing biofertilizer: Phosphorus, both native in soil and applied in inorganic fertilizers becomes mostly unavailable to crops because of its low levels of mobility and solubility and its tendency to become fixed in soil. The PSB

are life forms that can help in improving phosphate uptake of plants in different ways. The PSB also has the potential to make utilization of India’s abundant deposits of rock phosphates possible, much of which is not enriched. Azolla: is an aquatic fern, which contains an endophytic cyanobacterium Anabaena azollae in its leaves. It is used as a biofertilizer in rice field. Out of six species of Azolla, A. pinnata is widely employed as a successful biofertilizer in Indian rice fields. It adds 30 Kg of nitrogen per hectare where the yield is equivalent to that of urea or ammonium phosphate. Mycorrhiza as biofertilizer: Mycorrhiza is a root inhabiting fungus found around or inside the roots of many plants. It increases growth and yield and also provides protection to the roots against edaphic (soil) stresses, pathogen and pests. It helps in the increased uptake of soil and mineral water solution by the plant root system. It provides many uses for the host plants eg. VAM (Vesicular Arbuscular Mycorrhiza) fungi. Mycorrhiza is of two types. a. Ectotrophic mycorrhiza, which are found only outside the surface of roots of plants. eg. Basidiomycetous fungi. b. Endotrophic mycorrhiza, which are found inside the roots, in the intercellular spaces and even inside the cell (intra and intercellular) eg. VAM fungi. Benefits from biofertilizers 1. Biofertilizers are easy to produce in abundance and are available at low cost to the marginal farmers. 2. It increases soil fertility without causing any damage to the soil. 3. Application of biofertilizers increases yield upto 45 per cent and the left over biofertilizers in the soil increases yield as long as the biofertilizer remains in the soil up

to 3 to 4 years.

4. Azolla, which is a biofertilizer amends the soil with organic matter. Cyanobacteria in particular secrete growth promoting hormones like indole 3-acetic acid, indole butyric acid, naphthalene acetic acid, aminoacids, protein and vitamins to soil. 5. Cyanobacteria grow well both in acidic as well as in alkaline soils. Since, cyanobacteria are potent neutralizers, they help in the neutralization of soil. The

process of converting untenable, fallow land to cultivable soil is termed as soil reclamation. Blue green algae play a vital role in this conversion. 6. Symbiotic nitrogen fixing Rhizobium is a biofertilizer. It adds 50 to 150 Kg of nitrogen to soil per hectare. Azatobacter and Azospirillum secrete antibiotics which act as biopesticides. 7. Ectotrophic mycorrhiza, which acts as a biofertilizer, increases the surface area of the roots of host plants, so that more absorption of nutrients by the roots is made possible.