Author: Parmar Harshil Vinodbhai
Modern agriculture is heavily dependent on the fossil fuel based inputs such as chemical fertilizers, agrochemicals and energy intensive farm machinery. Excessive use chemical fertilizers causes the problem of growing nutrient imbalances in soil, deterioration of soil health, environment degradation and stagnation in crop yields, which is a great concern. Thus to reinforce the development of sustainable agriculture, use of bio-fertilizers has assured great promise to meet out the nutrients demand. The term 'Bio-fertilizers' denotes nutrient inputs for plant growth, which are biological origin. The bio-fertilizers restore the soil's natural nutrient cycle and build soil organic matter. The role of bio-fertilizers in agriculture production assumes special significance, particularly in the present context of expensive chemical fertilizers. Moreover, it can provide to the farmers a new strategy which is helpful for achieving the goal of increasing productivity. Keeping in mind the environment safety, food security and availability of resources, it becomes obligatory to harness their full potential (Mahajan et al., 2002; Mahajan et al., 2003a; Mahajan et al, 2003b; Gupta, 2006; Mahajan et al., 2008).
Beneficial bacteria, collectively called plant growth promoting rhizobacteria (PGPR), are the main constituents of biofertilizers. These bacteria promote plant growth and health by various means such as mineralization of nutritional elements, nodulation and nitrogen fixation (Zhang et al., 1996 ), synthesizing phytohormones such as hormones (Khalid et al. 2004 ), microbial iron transport agents or siderophores (Kloepper et al., 1980 ), antibiotic production against plant pathogens (Sandra et al. 2001 ; Morales et al, 2008 ), suppressing pathogens or combinations of them (Somers and Vanderleyden 2004 ). Nevertheless, the performance of PGPR as biofertilizers is severely influenced by both biotic and abiotic environmental conditions of the target regions.
"Bio-fertilizers refer to various inoculants or cultures containing a specific micro-organisms in concentrated form, which are derived either from nodules of plant roots or from the soil of root zone (rhizosphere) and posses unique ability to fix atmospheric N either by-living symbiotically with the roots of leguminous plants or non-symbiotically (free living) or to transfer native soil nutrients such as P, Zn, Cu, Fe, S etc. from the non-usable (fixed) form to usable form through biological processes".
- Merits in the use of Bio-fertilizer
- Due to escalating costs, the average consumption of chemical fertilizers is very low than the required level. Bio-fertilizers being cheap and non-bulky can fulfill the demand of fertilizer consumption.
- There is no ill effect on soil health and environment since bio-fertilizer is a natural product carrying living micro-organism derived from the plant root or cultivated soil.
- Besides their role in atmospheric N fixation and P solubilization, these also helpin stimulatingthe plant growth hormones providing betternutrient uptake and increased tolerance towards drought and moisture stress.
- A small dose of bio-fertilizer (300-500 g of material per hectare) is sufficient to produce desirable results because each gram of carrier ofa bio-fertilizer contains approximately 10 million viable cells of a specific strain.
- Bio-fertilizers reduce the pressure on the nonrenewable nutrient sources and thus help in conservation of renewable nutrient sources.
- Bio-fertilizers are harmless, improve soil properties and maintain soil fertility for sustainable agriculture.
- Marginal farmers in India can’t afford the chemical fertilizers, but the use of bio-fertilizers is affordable and economical for a wide variety of crops.
- The cost: benefit ratio of bio-fertilizers is always higher, so their use is acceptable in all places of cultivation.
- Bio-fertilizers also ensure the supply of essential micro-nutrients like Fe, Zn, Mn and Cu etc. for the augments of crop yields.
- Bio-fertilizers like Azotobacter and Azospirillum are very useful for dry land and rainfed farming as well as for irrigated areas.
- Certain bio-fertilizers may also work as bio-pesticide. For example, Azotobacterin strain 1006 has shown potential to inhibit seed borne pathogen in some cereals. The efficiency Azotobacterin isolated from local conditions can be increased by its use along with fresh farmyard manure (Gupta and Kaistha, 2007).
- Demerits in the use of Bio-fertilizer
- Shelf life of bio-fertilizers is the major constraints in the development of adequate market. Lower shelf life of bio-fertilizers carries some risk of recycling if it is not sold before expiry and this will sustain monitory loss to the marketing agency.
- Poor quality bio-fertilizers reaching farmers which are ineffective. Thus raising questions of their usefulness.
- Marketing of bio-fertilizers becomes difficult because the product contains living organisms.
- Lack of suitable carrier material for restoration and longevity in field conditions.
- Unavailability of proper transportation and storage facilities is also a major constraint for development of effective market.
- Faulty transport and storage system raising temperature which destroys the microbial population in inoculants.
- Poor and inconsistent crop response to bio-fertilizers.
- Unawareness and unavailability of bio-fertilizers to the farmers.
- Demand and production of bio-fertilizers is seasonal.
- Demand is limited because of poor and inadequate knowledge to the farmers about the usefulness of bio-fertilizers in increasing crop yields and soil productivity.
- Extension centers, by and large do not have well qualified technical sound staff that can face all technical problems.
- Existing soil conditions such as acidity, alkalinity, pesticides application and high nitrate level limit the N fixing capacity of the inoculants resulting in poor performance results of inoculants.
- Presence of certain toxic elements and deficiency of P, Cu, Co and Mo is unfavorable for bacterial fertilizers.
- There is no appropriate price mechanism of bio-fertilizer either at national or international level. Consumers have no idea on Ex-factory price of retail price. It has been also observed that some organizations are selling the same product at different prices which is quite illegal. This is the high time to formulate the strategy on pricing policy.
- Use of substandard inoculants or faulty inoculation techniques, any adverse effect of agro-chemical and unfavorable conditions like water-logging reduces the effectiveness of bio-fertilizers.
- Future Research Strategies/Priorities
- Bio-fertilizer technology needs to be refined for easy adoptability by the farmers. Microbial strains which can compete with indigenous ones and work over a wide range of soil climatic conditions need to be isolated and multiplied.
- Research should be done with regard to suitability of bio-fertilizers against adverse conditions.
- Suitable carriers for different microbes to ensure long shelf life and effectiveness.
- Encouragement and strong government support to small and marginal farmers about the benefits of bio-fertilizers.
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