An Overview of BioFertilizers In Sustainable Agriculture

With the introduction of green revolution technologies, modern agriculture is getting more and more dependent upon the steady supply of synthetic inputs. Intensive agriculture with the use of chemical fertilizers in large amounts has resulted in a manifold increase in the productivity of farm commodities but the adverse effects of these chemicals are clearly visible on soil structure, microflora, quality of water, food, and fodder. At this critical juncture, biofertilizers are useful to supplement chemical fertilizers.

Biofertilizers are natural and organic fertilizer that helps to keep in the soil with all the nutrients and live microorganisms required for the benefits of the plants. It’s used in organic farming, sustainable agriculture, green farming, and non-pollution farming. It is also one of the important components of integrated nutrient management, as they are a cost-effective and renewable source of plant nutrients to supplement the chemical fertilizers for sustainable agriculture.

The aim of biofertilizers is to complement and, where appropriate, replace conventional chemical fertilizers so that their use can be reduced with the resulting economic and environmental benefits.

Biofertilizer contains living microorganisms which, when applied to the soil, colonizes the rhizosphere or the interior of the plant and promotes growth by increasing the availability of primary nutrients to the host plant. They encourage plants to absorb, on their own, a greater quantity of nutrients which, even if they are naturally present in the soil, on occasions cannot be assimilated by plants because they are in an insoluble form. Conventional chemical fertilizers, however, supply the soil with chemical elements that, despite functioning as a fertilizer, can end up contaminating aquifers if they are not managed in the right dose and at the right moment.

 Drawbacks of Chemical Fertilizers

• Environmental stresses are becoming a major problem and productivity is declining at an unprecedented rate. Our dependence on chemical fertilizers and pesticides has encouraged the thriving of industries that are producing life-threatening chemicals and which are not only hazardous for human consumption but can also disturb the ecological balance.
•  Most of the problems associated with harvested crops and some of the pollution of our natural environment occurred as a result of inorganic fertilizer use.
• Most of the chemical fertilizers are imported and due to the high cost of importation, the price of the fertilizers becomes very high. Apart from the high cost, inorganic fertilizers when applied incorrectly, excessively or inadequately have negative effects.  
• Excessive fertilizer application leads to salt burn and in most cases leads to the death of young plants. 
• Because they are non-biodegradable, long term use of inorganic fertilizers results in the accumulation of harmful substances and acidification of the soil thereby causing a decrease in the fertility of the soil.
• Due to their high solubility in water, inorganic fertilizers applied to the soil could be leached deep into the soil (where plant roots cannot reach) and into underground water causing pollution. 
• Studies have shown that the application of nitrogen fertilizer in some weather conditions causes emission of nitrous oxide which has global warming affect potential 296 higher times than that of an equal mass of carbon dioxide.
• Methane emissions from crop fields (notably rice paddy fields) are increased by the application of ammonium-based fertilizers.

Types of Biofertilizers

The various types of biofertilizers which help the plant to grow at different levels of its growth are 

Nitrogen-fixing biofertilizers 

(Azotobacter, Nostoc, Rhizobium, Azospirillum) i. Increase soil nitrogen level ii. Fixes the atmospheric nitrogen in the soil and make it available to the plants

Phosphate biofertilizers 

Phosphorus solubilizing biofertilizers (Species of Bacillus, Pseudomonas, Penicillium, Aspergillus) Solubilize the insoluble phosphate from organic and inorganic phosphate sources, release insoluble phosphorus in soil and fix in clay minerals, secrete organic acids and lower the pH to dissolve bound phosphates in soil

Phosphorus mobilizing biofertilizers 

(Arbuscular Mycorrhiza, AM fungi) The fungus penetrates the cortical cells of the roots, increasing the surface area of roots, displace of absorption equilibrium of phosphate ions which increases the transfer of P ions, stimulate metabolic processes, Arbuscles absorb these nutrients into the root system.

Potassium solubilizing bio-fertilizer (KSB)

Examples include Bacillus Spp. and Aspergillus niger. Potassium in the soil occurs mostly as silicate minerals which are inaccessible to plants. These minerals are made available only when they are slowly weathered or solubilized. Potassium solubilizing microorganisms solubilize silicates by producing organic acids which cause the decomposition of silicates and helps in the removal of metal ions thereby making them available to plants. Potassium solubilizing biofertilizers are broad-spectrum bio-fertilizers.

 Potassium mobilizing bio-fertilizer (KMB)

Example of potassium mobilizing bio-fertilizer is Bacillus Spp. These work by mobilizing the inaccessible forms of potassium (silicates) in the soil. Some phosphate solubilizing bio-fertilizers such as Bacillus spp. and Aspergillus spp. has been found to mobilize potassium and also solubilize phosphorus.

Sulfur oxidizing bio-fertilizer (SOB)

 An example of sulfur-oxidizing microorganism is Thiobacillus spp. These work by oxidizing sulfur to sulfates which are usable by plants.

Biofertilizers for micro-nutrients (Bacillus sp.)

Bacterial species are Silicate and Zinc solubilizers, degrade silicates and aluminium silicates in soil, help in silicate weathering

Plant growth-promoting (Rhizobacteria) 

( Pseudomonas sp. and Bacillus sp.)  Act as both biofertilizer and biopesticides, promote growth by improved nutrient availability (biofertilizers), suppression of plant disease (bioprotectants), phytohormones production (biostimulants)

Compost (Cellulolytic fungi, Azotobacter)

Utilize animal dung to enrich the soil with microorganisms, eco-friendly organic fertilizer consists of nitrogen, phosphate solubilizing bacteria and various decomposing fungi, microorganisms break down organic matter (dead plants farmyard waste, cattle waste)

Liquid Biofertilizers

Liquid biofertilizers are suspensions having agriculturally useful microorganisms, which fix atmospheric nitrogen and solubilize insoluble phosphates and make it available for the plant. It reduces the use of chemical fertilizer by 15-40%, has a long shelf life, and it’s easy to produce and apply. Also, it helps to produce and manage organic crops so as to compete in the global market.

Nitrogen-fixing bio-fertilizers (NFB): Examples include Rhizobium Spp., Azospirillum spp. and blue-green algae; these work by fixing atmospheric nitrogen and converting them to organic (plant usable) forms in the soil and root nodules of legumes, thereby making them available to plants. Nitrogen-fixing biofertilizers are crop-specific bio-fertilizers.

Benefits of Bio-Fertilizer over Chemical Fertilizers

• Bio-fertilizers are environment-friendly and do not cause pollution, unlike inorganic fertilizers which often ‘run-off’ into water bodies causing eutrophication and ‘blue baby syndrome’ (acquired methemoglobinemia) when the nitrate level is above 10 mg/L. 
• Biofertilizers can help solve the problem of feeding an increasing global population at a time when agriculture is facing various environmental stresses. It is important to realize the useful aspects of biofertilizers and implement their application to modern agricultural practices. 
• The issue of excessive application does not arise in the use of bio-fertilizer and special skills are not required for its application.
•  Bio-fertilizers have long-lasting effects due to their slow nutrient release. The nutrients from bio-fertilizers are released to plants slowly and steadily for more than one season. As a result, long term use of bio-fertilizer leads to the buildup of nutrients in the soil thereby increasing the overall soil fertility.
•  Bio-fertilizers have been found to help the control of plant diseases such as pythium root rot, Rhizoctonia root rot, chill wilt, and parasitic nematode.
•  Disease control with bio-fertilizer has been attributed to four possible mechanisms: Successful competition for nutrients by beneficial microorganisms present in the fertilizer, production of antibiotics by the beneficial microorganisms, successful predation against pathogens by beneficial microorganisms, activation of disease-resistant genes in plants by the microorganisms.
• Bio-fertilizer acts as a soil conditioner adding organic matter to the soil which helps to bind the soil particles together preventing soil eructing, desertification, and erosion while increasing the water retention capacity of the soil.
•  It enriches the soil with beneficial microorganisms while boosting the already existing ones, unlike chemical inorganic fertilizers which acidify the soil making it hard for microorganisms to survive.
•  Bio-fertilizers contain a wide range of nutrients that are often absent in inorganic fertilizers (these include trace elements). 
• The composting of animal waste in a confined place or in an anaerobic condition (an important process in the production of bio-fertilizer), reduces the addition of methane to the atmosphere as these add methane to the atmosphere when left to decay on their own.
• Bio-fertilizer, when compared to raw (undegraded) organic manure, has the advantage of easier assimilation by plants and also the odor reduces after degradation. 
• Bio-fertilizer also contains useful microorganisms which may not be present in organic (degraded) fertilizer. 
• These bio-fertilizers can be produced from cheap waste materials that are abundant and the cost of production is low compared to inorganic fertilizers which required high energy.

Present Research Status of BioFertilizers

The new technology developed using the powerful tool of molecular biotechnology can enhance the biological pathways of the production of phytohormones. If identified and transferred to the useful PGPRs, these technologies can help provide relief from environmental stresses. However, the lack of awareness regarding improved protocols of biofertilizer applications to the field is one of the few reasons why many useful PGPRs are still beyond the knowledge of ecologists and agriculturists. Nevertheless, the recent progress in technologies related to microbial science, plant-pathogen interactions and genomics will help to optimize the required protocols. The success of the science related to biofertilizers depends on inventions of innovative strategies related to the functions of PGPRs and their proper application to the field of agriculture. The major challenge in this area of research lies in the fact that along with the identification of various strains of PGPRs and its properties it is essential to dissect the actual mechanism of functioning of PGPRs for their efficacy toward exploitation in sustainable agriculture.

Production and Demand of Biofertilizers

Production and Demand Biofertilizer productions are always demand-driven, the creation of demand among farmers is one of the most important steps required towards the promotion of biofertilizers. Research and development efforts by the government and research organizations have brought remarkable programs in production and wide use of Biofertilizers in the country, its potential requirement exceeds the actual production. For example in a sample of 411 field trials carried out across districts, plant responses to inoculation with Azotobacter in irrigated wheat were observed to be significant in 342 cases and ranged from 34 to 247. 

The estimated annual requirement of Rhizobium inoculum varies from 1,250 to 15,000t. The highest requirements of biofertilizers can be quantified through an over-simplified approach multiplying the total legume area by dosage per hectare; therefore if 25% of the area is annually treated, 3750t inoculum is needed for 30 MHA and the present production is about one-fourth of this. Based on crop area in India, the present requirement of biofertilizers is around 5,50,000 metric tonnes and there is ample potential to increase it to 50,000-60,000 tons by 2020; however, the total production in our country is much less than requirement which points out the inevitability of increase in biofertilizer production. Now, the government of India is boosting the biofertilizer industries by providing subsidies to a maximum of 20 lakh rupees and awarding a national productivity award to the efficient biofertilizer production unit. Agro Industries Corporation has the maximum production capacity which is followed by State Agriculture Departments, National Fertilizers Development Centers, State Agricultural universities and private sectors. 

Initiatives, taken by Government of India

The green revolution brought impressive gains in food production but with insufficient concern for sustainability. Dependence on chemical fertilizers for future agricultural growth would mean a further loss in soil quality, possibilities of water contamination and an unsustainable burden on the fiscal system. Consistent with the current outlook, the government aims not only to encourage their use in agriculture but also to promote private initiative and commercial viability of production. In India, the availability and affordability of fossil fuel-based chemical fertilizers at the farm level have been ensured only through imports and subsidies. 

The Government of India has been trying to promote an improved practice involving the use of biofertilizers along with fertilizers. These inputs have multiple beneficial impacts on the soil and can be relatively cheaper and more convenient to use. Failure of a market to build up the need for public intervention when the expected social gains from a relatively new product outweigh the costs, whereas the private gains do not and uncertainty about the product performance coupled with long periods of learning involved can lead to poor demand from who are farmers. 

Field studies have demonstrated them to be effective and cheap inputs, free from environmentally adverse implications that chemicals have. Moreover, Biofertilizers can act as a renewable supplement to chemical fertilizers and organic manures. They have the capacity to produce natural resistance in plants against pests and soil-borne diseases because antibodies are produced and beneficial microorganisms participate in the soil to increase fertility. 

For soil treatment, 500-800g of biofertilizers are mixed homogeneously with 10-15 kg of FYM and the mixture is added to soil at the time of sowing because Biofertilizers require organic manures after being added to the soil for their growth and development, as well as for their activity in the soil. But consistency in gains again eludes the trials conducted by All India Coordinated Pulse Improvement Project Transportation because distribution is a major problem in rural areas.

 There is an on-going attempt to promote Biofertilizers in Indian agriculture through public intervention, and in keeping with the spirit of the times, these policies motivate the private sector and the profit will help propel the new technology. Government of India and various State Governments have been promoting the nascent biofertilizer market both at the level of the user-farmer and the producer-investor through the following measures: 

(i) farm-level extension and promotion programs, 

(ii) financial assistance to investors in setting up units, (iii) subsidies on sales and

 (iv) direct production in the public sector and cooperative organizations and in universities and research institutions.

 The present expiry period is limited to 6 months which is related to the carrier (lignite/charcoal). 

Future Perspective of Biofertilizers

If biofertilizers impart certain social and long-term gains- for which private individuals may not be willing to pay- at least until the gains become ‘visible’, there is a rationale for spreading the cost over a larger group of beneficiaries or the society at large. However, wrong and untimely applications of artificial fertilizers adversely affect the natural balance of soil crop ecosystems, microbial ecology, and concern environment, resulting in a widespread decline in the crop yield. So, therefore, we have to curtail our dependence on chemicals and look for economical as well as an environmentally viable technology. Therefore, there is an upward trend in the demand for biofertilizers, Also India witnessed many families in the last century. The Green Revolution has changed the whole situation in India and made it self-sufficient in food production, but there is still no room for complacency. 

Biofertilizers offer a huge potential for widespread use offering both economical and environmental advantage to farmers/growers and commercial viability to production units various research groups/organizations are engaged in research and development on biofertilizers and have made their efforts to increase the application of biofertilizers.

Assuring the quality of products, concepts of food security and the concept of safe food with extensive field-based testing, capacity building of resource persons and stakeholders on standard production processes, storage, and application will help a wider adoption and popularisation of biofertilizers.

To know more about Environment, 

Saalumarada Thimmaka, The Environmentalist