The increased demand for food because of the expanded population has forced the agricultural world to mass produce crops. In doing so, the farmers have been using harmful chemicals to increase crop yield without knowing its detrimental effect. These hazardous chemicals lessen the quality of soil, threaten human health, and at the same time, pollute the environment. The world needs a sustainable solution which is likely to happen with bio-fertilizer to reduce such impacts.
Bio-fertilizer is an organic fertilizer that uses live organisms for better absorption of plant nutrients and to enhance plant growth and development. For instance, an earlier report found that incorporating bio-fertilizer with Acidithiobacillus bacteria boosted the nutrient intake of sugarcane and improved the availability of nutrition, i.e., nitrogen, phosphorous, and potassium in the soil. (1) Bio-fertilizer is integral to sustainable development and strengthening crop yield. It can improve human health and lessen earth, water, and air degradation. Bio-fertilizers are available in solid and liquid form containing beneficial soil microbes (such as Rhizobium and Azotobacter) with a shelf life of 6 months to 2 years. In addition, it benefits plant growth and can be used as fish feed. (2)
Table of Contents
Types of bio-fertilizer
The types of bio-fertilizers are classified based on their work. Nitrogen-fixing bacteria fix the nitrogen in the air and carry symbiotic relations with plants. In contrast, phosphate-solubilizing plants solubilize the fixed phosphorous in the soil, making it available to the plants. Similarly, mycorrhizae (phosphate mobilizing) are another essential bio-fertilizer which (other than storing the nutrient, especially phosphorous and potassium to some extent) protects the symbiotic fungus and nematodes and eliminates the toxic compounds like phenolic that hinder nutrient uptake.
This type of fertilizer is usually associated with symbiotic and non-symbiotic microbes. The symbiotic organism includes Rhizobium, Frankia, and Anabaena azollae (symbiotic), Azotobacter, Clostridium, Blue-green algae, Azolla, Acetobacter, Nostoc, and Anabaena (free-living), Azospirillum (associate symbiotic). These fertilizers either directly bond with plants having a mutualistic relationship (for example, help in root nodulation) or live freely in the soil and fix the nitrogen. Plants later absorb the fixed nitrogen. It is evaluated that inoculation of Rhizobium fixes nitrogen (around 40-250 kg N/ha/ year) by various legume plants. Also, about 2-15 mg/g of carbon is fixed by Azotobacter chroococcum in a culture media. Likewise, Azosprillium fixes 20- 40 kg N/ha/year of nitrogen in non-leguminous plants such as cereals, and millets. Azolla fixes nitrogen about 40-60 kg N/ha/year per rice crop.
Phosphate mobilizing fertilizer
Phosphate mobilizing fertilizer (Mycorrhizae): Mycorrhizae are fungal species that colonize the root system and play a mutualistic relationship with 80% of the land plant. They depend on plants for photosynthesis and energy; in exchange, they provide an abundance of merits to the plants, such as improvement in the uptake of nutrients such as potassium, phosphorous, vitamins, and minerals (calcium, Zinc) by secreting enzymes and releasing organic matter. It improves the hydraulic conductivity of roots in the soil and plants’ drought tolerance. It extends the hyphae to the soil to hold the soil particles together and enhance the soil structure protecting against soil erosion. The addition of this fertilizer boosts the activity of phenolic and phytoalexin compounds, which increases the defense mechanism of plants against a variety of soil-related diseases—examples: Laccaria spp, Scutellospora sp., and Sclerocytis sp.
Mineral solubilizing fertilizer
The plant requires minerals such as Zinc and calcium in a trace amount. As this mineral is not abundant, its external addition to overcoming its deficiencies can be costly. However, the mineral solubilizing fertilizer solves the problem. For instance, this fertilizer’s inoculant solubilizes the insoluble zinc compound such as zinc oxide, zinc carbonate, and zinc sulfide into a soluble form. Bacillus subtilis and Thiobacillus thioxidans are examples.
It is a mass of decomposed organic matter of plants, animal dungs, fruits, straw, and sewage sludge along with microorganisms, earthworms, and 2% (w/w) of nitrogen, phosphorus, and potassium. Oxidation caused by the organism’s movement using the organic matter present in fertilizer forms the humus-containing materials, which increase the biodiversity of soil, provide nutrients to the crop, keep the soil moist, and suppress the other pathogenic and parasitic organisms. Some organisms used in this fertilizer are Trichoderma viridae and Aspergillus niger.
Application of bio-fertilizer
The application of bio-fertilizer is different in different crops.
Some of them are described below:
This method is effective for all types of microbial inoculants. The seed is mixed and uniformly covered with a slurry containing the inoculation (one packed, i.e., 200g is enough for 10 kg of seeds). Next, the seed is brought for shade drying for about 30 minutes and then seeded in the ground within 24 hrs.
Seedling root dip
This method is applicable for transplanted plants such as vegetables, cereals, fruits, and sugarcane. The roots of this plant are dipped in the mixer (40 liters of water and two packets of inoculant) for 5 to 10 min and then transplanted back(3). Some example of bio-fertilizer employed is nitrogen fixing Azotobacter and phosphorous solubilizing fertilizers. (4)
The biofertilizer is mixed directly into the soil or combined (four packets of inoculants blended with 20 kg of dried manure). For instance, Rhizobium is applied for leguminous plants, Azotobactor for tea, coconuts, and Azolla for rice. (3)
Advantage of bio-fertilizer
The bio-fertilizer holds numerous advantages over chemical fertilizer, which are explained below:
- The bio-fertilizer solubilizes the insoluble phosphate in soluble form and makes it available for plants to grow and develop.
- They take up the nitrogen from the atmosphere, convert it into the nitrogenous compound in the soil, and make it accessible to plants. This process is known as nitrogen fixation.
- The bio-fertilizer is more efficient than chemical fertilizers, which increases soil fertility, improves economic values, and expands the plant’s uptake of vitamins, minerals, and other nutrients.
- Bio-fertilizer acts as a renewable energy source that helps coordinate friendly the environment. It doesn’t pollute the ecosystem. Instead, it is eco-friendly.
- Bio-fertilizer protects living organisms from soil erosion by producing capsular polysaccharides, which help to hold the soil more tightly and also prevent water retention from the soil.
- Bio-fertilizer plays a significant role in protecting plants against drought and soil-borne diseases.
- Bio-fertilizer is imperative in depositing excess carbon dioxide, reducing global warming, and conserving biodiversity. (5)
Disadvantages of bio-fertilizer
Despite the advantages, bio-fertilizer has few demerits.
- Bio-fertilizer is more efficient than chemical fertilizer, but it doesn’t substitute chemical fertilizer as the crop productivity is less (20%-30%) with the use of bio-fertilizer when compared with the chemical.
- Bio-fertilizer needs an aseptic environment during their manufacture. Contamination can harm its production.
- Microbes in bio-fertilizer are light sensitive, so prolonged exposure to sunlight can kill them.
- The life span of a bio-fertilizer is six to two years, so it must be used within it.
- The specific bio-fertilizer is used for particular crops only. To take an instance, only specific Rhizobium is used for root nodulation.
- The effectiveness of bio-fertilizer depends on the soil’s physical and chemical properties, such as moisture, pH, temperature, organic matter, and microbes present in the soil.
- Djajadi, Syaputra R, Hidayati SN. Effect of NPK fertilizer, biofertilizer containing N fixer and P solubilizer, and green manure of C. juncea on nutrients uptake and growth of sugarcane. IOP Conf Ser Earth Environ Sci. 2020;418(1).
- Ajmal M, Ali HI, Saeed R, Akhtar A, Tahir M, Mehboob MZ, et al. Biofertilizer as an Alternative for Chemical Fertilizers. Res Rev J Agric Allied Sci [Internet]. 2018;7(1):1–7. Available from: http://www.rroij.com/open-access/biofertilizer-as-an-alternative-forchemical-fertilizers.php?aid=86649.
- Rana R, Ramesh, Kapoor P. Bio-Fertilizers and Their Role in Agriculture. Pop Kheti. 2013;1(1):56–61.
- Khare E. Biofertilizers : types , production and application Biofertilizers.
- Planning B, Unit D, Agricultural N, Project I. Opportunities for biofertilizer industry. 482004.
- Repac, Ivan & Parobeková, Zuzana & Sendecky, Matus. (2017). Reforestation in Slovakia: History, current practice and perspectives. Reforesta. 3. 53-88. 10.21750/REFOR.3.07.31.