The agriculture industry is the backbone of human development. It has a contribution of about one-third of the global gross domestic product. Unfortunately, due to the extreme growth in the human population, it is getting difficult to feed the growing population which is estimated to rise up to 9.5 billion by 2050. This will lead to high food demand.

Furthermore, the unavailability of enough fertile land, over-urbanization, unpredictable weather, the uncertainty of climate change, and addition to that are biotic and abiotic stresses make up for the constraints in producing the majority of crops. Besides, there is uneven soil quality, limited or no nutrients, environmental conditions, as well as the biological health of the soil are other major concerns. This affects crop yield per unit area for achieving the targeted goal of food security. Due to industrialization and green revolutions with developed technologies, around the world, agriculture was introduced to chemical fertilizers (consisting of N, P, or K) that were excessively used to increase the production and efficiency of crop production.  

Thus, increasing the nutrient content of the soil and at the same time degrading the quality of the soil. But, irrespective of the number of chemical fertilizers used, the plants can absorb only a limited amount (30–40%) of these nutrients because of low fertilizer-use efficiency and rest is lost to soil causing environmental pollution. Moreover, heavy metals and radio nuclides are present in chemical fertilizers, which stay in the soil for a long time and are difficult to degrade. These heavy metals further become persistent pollutants in nature that can end up making the soil infertile. Another big issue with the application of excessive chemical fertilizers is the eutrophication of water sources.

Let us go through some of the important adverse effects of chemical fertilizers that will explain the need to have alternative technology. One of the concerning issues facing the use of chemical fertilizers is groundwater contamination which is an environmental disaster. Nitrogen in fertilizers is known to break down into nitrates and can travel easily through the soil. The nitrates are water-soluble and can remain in groundwater for many years adding more nitrogen over the years as an accumulative effect.Another component of chemical fertilizer is urea which produces ammonia, which is responsible for acid rain, groundwater contamination, and ozone depletion due to the release of nitrous oxide by the denitrification process. Another important harmful effect of chemical fertilizers is of extreme air- and water-borne nitrogen from fertilizers may cause respiratory disorders like cardiac ailments, along with different kinds of cancers.

Biofertilizers play a crucial role in sustainable agriculture and have several important benefits. Here are some key reasons why biofertilizers are important: They are a natural source of nutrition enriched with the right amount of minerals and essential elements required for plant growth. Biofertilizers are made from natural biological elements and hence are degradable and environmentally friendly. These biofertilizers have the potential to reduce the dependency on chemical fertilizer dependency. Their use in soil has been observed to enhance plant growth and productivity thus promoting sustainable agriculture practices. The application of biofertilizers helps improve soil fertility and prevents land degradation. Last, but not least, the plants grown and crops produced on such fields are healthier and tasty.

The following are highlights of recent developments in biofertilizer production:

Microbial/Fungi

Mycorrhizal fungi enhance the plant’s ability to absorb nutrients, particularly phosphorus, from the soil. They also improve water uptake and provide plants with increased resistance to environmental stress, such as drought and disease. Some commonly used mycorrhizal fungi species include Glomus spp., Rhizophagus irregularis, and Tricholoma matsutake. Trichoderma fungi are widely used in biofertilizers and biocontrol agents. They can promote plant growth, enhance nutrient availability, and suppress plant pathogens. Examples: Trichoderma harzianum, Trichoderma viride, and Trichoderma reesei are common species used in biofertilizers.

Oyster mushroom is a popular edible fungus that can also be utilized as a biofertilizer. The spent mushroom substrate (SMS) or the residual material after mushroom cultivation can be applied to agricultural fields as an organic amendment. SMS contains significant amounts of organic matter and nutrients, improving soil fertility and enhancing microbial activity. Arbuscular mycorrhizal fungi form associations with a wide range of plants, including crops, vegetables, and trees. These fungi establish symbiotic relationships with the host plants, enhancing nutrient uptake, especially phosphorus, and improving plant growth and productivity. Although primarily known as a biocontrol agent for pest management, Beauveria bassiana can also act as a biofertilizer. This entomopathogenic fungus colonizes plant roots, promoting root development and nutrient absorption. It can enhance nutrient availability, particularly nitrogen, and improve plant growth.

Some biofertilizers utilize a combination of different mycorrhizal fungi species to form a consortium. These consortia include multiple species of mycorrhizal fungi, each with unique benefits. The combined use of different mycorrhizal species can provide a broader range of benefits, including enhanced nutrient uptake, improved soil structure, and increased plant resilience. Shiitake mushroom cultivation generates spent mushroom substrate (SMS), which can be repurposed as a biofertilizer. The SMS contains organic matter, nutrients, and residual mycelium, making it beneficial for soil fertility and plant growth. The application of Shiitake SMS can improve soil structure, nutrient availability, and microbial activity.

Azospirillum is a group of nitrogen-fixing bacteria that establish a symbiotic relationship with plant roots. These bacteria can fix atmospheric nitrogen and convert it into a plant-usable form. Azotobacter is another group of nitrogen-fixing bacteria that colonize the rhizosphere of plants. They are particularly effective in non-legume crops. Rhizobium bacteria form a symbiotic relationship with leguminous plants, such as soybeans, peas, and clovers. These bacteria infect the plant roots and develop specialized structures called nodules, where they fix atmospheric nitrogen. Bacillus bacteria are widely used as biofertilizers due to their versatile properties. They can promote plant growth by various mechanisms, including nutrient solubilization, production of plant growth-promoting substances, and disease suppression.

Biofertilizer for Hydroponics:

Hydroponics is the future of next-generation agriculture and knowing the biofertilizers used for the process is crucial. There are many microbial biofertilizers used for hydroponic agriculture, which are already mentioned above. Following are the new trends in biofertilizers that can be used for hydroponics.

Enzyme-Based Biofertilizers: Enzyme preparations derived from microbial sources can be used as biofertilizers in hydroponics. These enzymes help break down organic matter and release nutrients in a readily available form for plant uptake. Enzyme-based biofertilizers can enhance nutrient cycling, improve nutrient availability, and promote healthy root development.

Cyanobacteria: Cyanobacteria, also known as blue-green algae, can fix atmospheric nitrogen and provide it to plants in a usable form. Some cyanobacteria species, such as Anabaena and Nostoc, have been used as biofertilizers in hydroponics to supplement nitrogen requirements. They can be added to the nutrient solution or used as a foliar spray.

Seaweed Extracts: Seaweed extracts derived from various seaweed species, such as Ascophyllum nodosum and Sargassum sp., are commonly used as biofertilizers in hydroponics. They are rich in plant growth-promoting substances, micronutrients, and trace elements. Seaweed extracts can stimulate root growth, enhance nutrient uptake, and improve plant vigor.

It is not mandatory to discover new technologies that are always complicated and difficult to understand. In this article, we learn that to achieve sustainable agriculture, simple, natural, and known knowledge is enough to achieve sustainable development. Biofertilizers are not at all complex, they come straight from the natural world. We humans, need to understand its potential to rescue the environment and at the same time provide abundant food for all of us. Readers more interested in this topic can read about different articles present in the prior art.

Reference:

1. Satish Kumar,  Diksha, Satyavir S. Sindhu, Rakesh Kumar, Biofertilizers: An eco-friendly technology for nutrient recycling and environmental sustainability, Current Research in Microbial Sciences, Volume 3, 2022, 100094, ISSN 2666-5174, https://doi.org/10.1016/j.crmicr.2021.100094.
2. Divjot Kour, Kusam Lata Rana, Ajar Nath Yadav, Neelam Yadav, Manish Kumar, Vinod Kumar, Pritesh Vyas, Harcharan Singh Dhaliwal, Anil Kumar Saxena, Microbial biofertilizers: Bioresources and eco-friendly technologies for agricultural and environmental sustainability, Biocatalysis and Agricultural Biotechnology, Volume 23, 2020, 101487, ISSN 1878-8181, https://doi.org/10.1016/j.bcab.2019.101487.