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Nano-biofertilizers for sustainable soil and environment

cross-linking process, which ensures ease of handling In summary, Top-down fabrication is simple but
and consistent field performance. 54-56 energy-intensive and more challenging when it comes
to controlling particle size, whereas bottom-up is more
5.2. Biological (green) synthesis precise and controllable but may require complex inputs. 59
Green synthesis utilizes the natural biochemical
pathways of living organisms – bacteria, fungi, algae, 5.5. Economic and scalability considerations
or plants – to reduce metal salts into nanoparticles. This Each synthesis method varies in cost, efficiency, and
bottom-up approach is eco-friendly, avoids the use of scalability. Encapsulation and biosynthesis are eco-
hazardous chemicals, and aligns with organic farming friendly but slower and less uniform. Chemical synthesis
practices. Certain microbes, such as filamentous fungi is effective and precise but costly and infrastructure-
or actinobacteria, can precipitate nanoparticles like zinc intensive. Top-down methods are straightforward but
oxide (ZnO), iron oxide, or selenium through enzymatic may not yield optimal nanostructures.
activity. For example, extracts from Chlorella vulgaris For large-scale farming, low-cost biological or
have been used to synthesize iron oxide nanoparticles, precipitation methods may be best, whereas, for high-
which possess antifungal and plant-growth-promoting value crops, more expensive encapsulated fertilizers
properties. In addition, Aspergillus species have been may be justified.
employed to produce nano-phosphate fertilizers, which Overall, each method plays a specific role:
have shown promising results in maize cultivation. Some Encapsulation combines slow-release with microbial
key advantages of this method are its biocompatibility, low protection; green synthesis is sustainable and chemical-
energy requirements, and sustainability. However, some free; chemical synthesis offers high precision; and hybrid
challenges remain, including low productivity, variable methods strike a balance between cost and efficiency. 60
particle size, and difficulty in large-scale standardization. 57 Despite the diversity of methods used to manufacture
nano-biofertilizers, there is significant variation in
5.3. Chemical synthesis methods economic efficiency and industrial scalability. For
Chemical techniques such as sol-gel, hydrothermal example, chemical methods such as pyrolysis or
synthesis, and co-precipitation are widely used in the co-precipitation are effective in producing homogeneous
production of nanofertilizers. These methods allow for particles with high precision, but they are expensive and
precise control over particle size and purity. For instance, require complex technical infrastructure. In contrast,
nano-hydroxyapatite, which is synthesized through biosynthesis using microorganisms or plant extracts
hydrothermal methods, has demonstrated improved represents a lower-cost and more environmentally
phosphorus availability and 20%–30% higher yields friendly alternative, but it still faces challenges in
in soybean and wheat when compared to conventional standardizing the physical properties of the produced
phosphate fertilizers. particles. Therefore, evaluating the effectiveness of
Another example is nano-urea, which has been these technologies is not limited to release efficiency
commercialized by the Indian Farmers Fertilizer or stability. Economic factors, such as raw material
Cooperative (IFFCO) and is produced through industrial and energy costs, and the potential for commercial
encapsulation and reverse osmosis. The main benefits scalability to meet the requirements of large-scale
include uniformity, effectiveness, and adaptability. agriculture, must also be considered.
However, there are some limitations associated with These methods highlight the diverse approaches
this method, such as high production costs, chemical in the production of nano-biofertilizers, with each
residues, and the need for advanced equipment. 58 beneficial microorganism and technology used for
nutrient nanoparticle loading playing a unique role in
5.4. Top-down versus bottom-up nanofabrication enhancing nutrient delivery and promoting sustainable
In top-down fabrication, bulk materials are broken down agricultural practices.
into nanoparticles through physical methods such as ball
milling or grinding. For example, rock phosphate has 6. The role of nano-biofertilizers in sustaining
been milled into nanophosphate particles and combined soil fertility
with microbial solubilizers to improve nutrient
availability in calcareous soils. Bottom-up approaches, Soil fertility quite plays an important role in
as discussed above, assemble particles from atoms or determining agricultural productivity as well as the
molecules using biological or chemical processes. sustainability of ecosystems. Conventional chemical

Volume 22 Issue 3 (2025) 21 doi: 10.36922/AJWEP025160123