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Although chemical fertilizers increase crop productivity, they create an imbalance in the soil's mineral content and decrease soil fertility. Large-scale use of chemical fertilizers causes irreparable damage to the soil structure and soil microbial flora. It affects the food chains across ecosystems responsible for heritable mutations in future generations of consumers.
The rapid growth in the world population has increased the demand from the agricultural sector, making researchers wary of the overuse of chemical fertilizers by farmers. Nano-fertilizers have emerged as a promising alternative that ensures high crop production and soil restoration.
Why is the Use of Nano-Fertilizers Better than Conventional Fertilizers?
The unique properties of nanoparticles, such as high sorption capacity, the increased surface to volume ratio, and controlled-release kinetics to targeted sites, make them a potential plant growth enhancer.
Because of these characteristic features, nano-structured fertilizers can be used as a smart delivery system of nutrients to the plant. Nano-fertilizers are released very slowly in comparison to conventional fertilizers. This approach improves nutritional management, i.e., increasing the nutrient-use efficiency and decreasing nutrient leaching into groundwater.
Nano-fertilizers are specifically designed to release active ingredients in response to biological demands and environmental stress. Scientists have further stated that nano-fertilizers increase agricultural productivity by improving photosynthetic activity, seedling growth, rate of seed germination, nitrogen metabolism, and carbohydrate and protein synthesis.
Development of Effective Nano-Formulations
Nano-formulations or nano-sized fertilizers are made from ammonium humate, ammonia, urea, peat, plant wastes, and other synthetic fertilizers. An example of nano-formulation is nano-sized nitrogen (N) fertilizer which is prepared as a result of deposition of urea on calcium cyanamide.
Nano nitrogen fertilizers are instrumental in enhancing the productivity of rice. This is regarded as an excellent alternative to chemical fertilizers because it promotes growth and reduces environmental pollution. Excessive use of conventional fertilizers causes environmental pollution by leaching, denitrification, and volatilization of chemical fertilizers.
Another effective nano-fertilizer has been formulated by grinding urea and mixing it with different biofertilizers. This nano-fertilizer offers a slow and gradual release of nutrients for a more extended period.
Nano-fertilizers are developed using both mechanical and biochemical processes, i.e., materials are grounded to obtain nano-sized particles through mechanical means and biochemical techniques are employed to obtain effective nanoscale formulations.
Fertilizers are often encapsulated within nanoparticles. Such nano-fertilizers offer a greater absorption capacity and nutrient use efficiency to the plant. The process of encapsulation of nutrients with nanomaterials can be performed in three ways. These are stated below
- Nutrient particles coated with a thin layer of nanomaterials (polymer film)
- Nutrients encapsulated within the nanomaterials of varying nature and chemical composition
- Nutrients delivered in the form of nano-emulsion
How Do Nano-Fertilizers Enter the Plant System?
Researchers have stated that the plant root system, which is the gateway for the nutrients, is highly porous to nanomaterials (nano-fertilizers) than conventional fertilizers. Stomatal openings in leaves are also reported to favor uptake of nanomaterials and their entry to leaves.
Scientists have conducted experiments using the faba bean (Vicia faba), to determine the nanoparticle's efficiency to penetrate the plant system. They found that nanoparticles (43 nm in size) could penetrate leaf in large numbers compared to nanoparticles larger than 1.0 nm size.
Nano-fertilizers are also reported to deliver nutrients through plasmodesmata. Plasmodesmata are nano-sized channels of approximately 50–60 nm size used to transport ions between cells. Carbon nanotubes and silica nanoparticles are useful tools for transporting and delivering cargoes (nutrients and other important biochemicals) to plants' target site.
Use of Nano-Fertilizers in Sustainable Crop Development
Scientists believe that zinc nano-fertilizers are responsible for robust plant growth (shoot and root system) and increase the leaves' chlorophyll content.
In a previous study, the amendment of zinc nano-fertilizers significantly increased the yield of peanuts. These nano-fertilizers also improve seed production of vegetables. Similarly, carbon nanotubes containing fertilizers were reported to decrease the days to germination. These nano-fertilizers were also found to promote the development of plant root systems in rice seedlings.
Nano-fertilizers also reduce the crop cycle period and increase crop yield. For example, the amendment of nanoparticles carrying NPK (nitrogen, phosphorus, and potassium) to wheat showed an increase in grain yield and reduced the crop cycle of wheat by 40 days. Similar results were obtained in the maize cropping system.
Limitations of Nano-Fertilizers
Despite aiding in sustainable crop production, limitations of nano-fertilizers should be carefully considered before marketing. The limitations of using nano-fertilizers mainly arise due to the absence of rigorous monitoring and research gaps.
Some of the drawbacks associated with the use of nano-fertilizers for sustainable crop production are enlisted below.
- Lack of a nano-fertilizer risk management system
- Lack of production and availability of nano fertilizers in required quantities. This limits the wider scale adoption of nano-fertilizers as a source of plant nutrients.
- The high cost of nano fertilizers
- Lack of standardization in the formulation process. This brings about different results of the same nanomaterial under various pedoclimatic conditions.
Approved Nano-Fertilizer Manufacturing Companies
Some of the approved nano-fertilizers used in the world today and their manufacturers are:
- Nano Calcium (AC International Network Co., Ltd., Germany)
- Nano-Micro Nutrient (Shan Maw Myae Trading Co., Ltd., India)
- Nano Green (Nano Green Sciences, Inc., India)
- Biozar Nano-Fertilizer (Fanavar Nano-PazhooheshMarkazi Company, Iran)
References and Further Reading
Zulfiqar, F. et al. (2019) Nanofertilizer use for sustainable agriculture: Advantages and limitations. Plant Science. 289:110270. https://doi.org/10.1016/j.plantsci.2019.110270
Al-Juthery, H.W.A. et al. (2019) Effect of foliar nutrition of nano-fertilizers and amino acids on growth and yield of wheat. Conference Series: Earth and Environmental Science. 388, 012046. https://doi.org/10.1088%2F1755-1315%2F388%2F1%2F012046
Muhammad, A.I. (2019) Nano-Fertilizers for Sustainable Crop Production under Changing Climate: A Global Perspective. https://www.intechopen.com/books/sustainable-crop-production/nano-fertilizers-for-sustainable-crop-production-under-changing-climate-a-global-perspective
León-Silva, S. et al. (2018) Design and Production of Nanofertilizers. In: López-Valdez F., Fernández-Luqueño F. (eds) Agricultural Nanobiotechnology. Springer, Cham. https://doi.org/10.1007/978-3-319-96719-6_2
Solanki, P. et al. (2015) Nano-fertilizers and Their Smart Delivery System. In: Rai M., Ribeiro C., Mattoso L., Duran N. (eds) Nanotechnologies in Food and Agriculture. Springer, Cham. https://doi.org/10.1007/978-3-319-14024-7_4