Modernized agricultural methods play a significant role in meeting the food demands of a growing world population, which has also led to an increasing dependence on chemical fertilizers and pesticides. The term “chemical fertilizer" refers to any number of synthetic compound substances created specifically to increase crop yield and composed of known quantities of nitrogen, phosphorus, and potassium, and their exploitation causes air and groundwater pollution by eutrophication of water bodies. Because of this, recent attention has been given to developing an environmentally friendly bio fertilizer.
The new trend in agricultural production is the use of biological-based organic fertilizers as an alternative to agro-chemicals. This means that soil fertilization relies on organic inputs to improve nutrient supply and conserve field management. Organic farming is one such strategy that not only ensures food safety but also adds to the biodiversity of the soil. The additional advantages of bio fertilizers include longer shelf life, causing no adverse effects to the ecosystem. Bio fertilizer is made up of free living bacteria that promote plant growth, increase productivity through root strengthening, and help to reduce the amount of synthetic fertilizer used on crops.
Organic farming is mostly dependent on the natural microflora of the soil, which constitutes all kinds of useful bacteria and fungi, including the arbuscular mycorrhiza fungi (AMF) and plant growth-promoting rhizobacteria (PGPR). Through nitrogen fixation, phosphate and potassium solubilization or mineralization, the release of plant growth regulating substances, the production of antibiotics, and the biodegradation of organic matter in the soil, biofertilizers keep the soil environment rich in all types of micro- and macronutrients.
When bio fertilizers are applied as a coating for seeds or directly as soil inoculants, the microbes present multiply and participate in nutrient cycling, boosting crop productivity.
In general, 60% to 90% of the total applied fertilizer is lost, and the remaining 10% to 40% is taken up by plants in the traditional use of chemical fertilizer. In this regard, microbial inoculants have paramount significance in integrated nutrient management systems to sustain agricultural productivity and a healthy environment. The PGPR or co-inoculants of PGPR and AMF can increase the nutrient use efficiency of fertilizers.
The rhizosphere, which is the narrow zone of soil surrounding plant roots, can comprise up to 1011 microbial cells per gram of root and over 30,000 prokaryotic species. There are microbial strains providing numerous services to crop plants, like organic matter decomposition, nutrient acquisition, water absorption, nutrient recycling, weed control, and bio-control. Rhizosphere microbial communities are an alternative to chemical fertilizers and have become a subject of great interest in sustainable agriculture and bio-safety programs.
A major focus in the coming decades will be on safe and environmentally friendly methods of sustainable crop production by utilizing beneficial microorganisms.Such microorganisms, in general, consist of diverse naturally occurring microbes whose inoculation into the soil ecosystem advances soil physicochemical properties, soil microbe biodiversity, soil health, plant growth and development, and crop productivity. The agriculturally useful microbial populations include plant growth promoting rhizobacteria, N2-fixing cyanobacteria, mycorrhiza, plant disease suppressive beneficial bacteria, stress tolerance endophytes, and bio-degrading microbes.
These biofertilizers are a supplementary component to soil and crop management traditions. Azotobacter, Azospirillum, Rhizobium, cyanobacteria, phosphorus and potassium solubilising microorganisms, and mycorrhizae are some of the PGPRs that were found to increase in the soil under no tillage or minimum tillage treatment. Efficient strains of Azotobacter, Azospirillum, Phosphobacter, and Rhizobacter can provide a significant amount of nitrogen to plants and increase the plant height, number of leaves, stem diameter, percentage of seed filling, and seed dry weight. Similarly, in rice, the addition of Azotobacter, Azospirillum, and Rhizobium promotes the physiology and improves the root morphology.
References
Abbaszadeh-Dahaji, P., Masalehi, F., and Akhgar, A. (2020). Improved growth and nutrition of sorghum (Sorghum bicolor) plants in a low-fertility calcareous soil treated with plant growth–promoting rhizobacteria and Fe-EDTA. J. Soil Sci. Plant Nutr.
Agnolucci, M., Avio, L., Pepe, A., Turrini, A., Cristani, C., Bonini, P., et al. (2019). Bacteria associated with a commercial mycorrhizal inoculum: community composition and multifunctional activity as assessed by illumina sequencing and culture-dependent tools.
Ahmed, B., Midrarullah, and Sajjad Mirza, M. (2013). Effects of inoculation with plant growth promoting rhizobacteria (PGPRs) on different growth parameters of cold area rice variety, Fakre malakand. Afr. J. Microbiol.
Ahmed, E., and Holmström, S. J. M. (2014). Siderophores in environmental research: roles and applications. Microb. Biotechnol.
Alori, E. T., Glick, B. R., and Babalola, O. O. (2017). Microbial phosphorus solubilization and its potential for use in sustainable agriculture.
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