This article was updated July 2023.
Global food security is under serious threat worldwide because of the limited availability of natural resources such as fertile land, quality seeds, and water. Global warming also threatens food security due to the devastating impact of rising global temperatures on agriculture. Nanofetilizers may offer a solution to improve food security while reducing the impact of agriculture on the land.
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Why Is Nanofertilizer Important for Food Security?
It has been estimated that the world’s population (currently eight billion people) will increase to approximately nine billion by 2050. Food production will need to double (compared with 2009 production) to meet the rising demand for food. Currently, an estimated 811 million people go to bed hungry each night globally.
Global agricultural systems will need to rapidly respond to the growing population by producing higher volumes of food; if not, millions more people will go hungry. Food systems, however, are facing numerous unprecedented challenges, including rapid climatic changes.
Fertilizers play a vital role in increasing agricultural production, but excessive use of chemical fertilizers irreversibly damages the chemical ecology of soil and reduces the available area for crop production. Chemical fertilizers, therefore, inadvertently contribute to food insecurity in the long term by damaging fertile land.
Agricultural practices that do not harm the planet must be implemented globally so that food production can be guaranteed for generations to come. One solution may come from nanofertilizers, which do not rely on the heavy use of harmful chemicals.
How Can Nanofertilizers Benefit Agriculture?
In conventional agriculture, an excess of fertilizer is applied directly into the soil or sprayed on the leaves, surpassing the plant's nutritional need. This is because a very low percentage of fertilizer reaches its target site due to leaching of chemicals, evaporation, drift, hydrolysis, run-off, and photolytic or microbial degradation.
This excess of chemical fertilizer negatively affects the nutrient equilibrium of the soil and causes contamination of local water supplies due to the leaching of toxic materials into water bodies.
Switching from a conventional fertilizer to nanofertilizer could reduce the amount of chemicals used while simultaneously increasing crop yield. Nanofertilizers do this via various mechanisms, including increasing nutrient uptake, controlling the release of nutrients, and targeting nutrient delivery. Using a nanofertilizer can also reduce the environmental impact of agriculture.
Nanofertilizers: Increased Nutrient Uptake
Nanoparticles used in nanofertilizers measure just 1-100 nanometers in lengths of two or three dimensions. Their small size gives them unique properties compared with their bulk material counterparts. Due to their small size, nanoparticles have a large surface area-to-volume ratio, so a nanofertilizer can deliver a greater amount of nutrients to crops than conventional fertilizers.
Nanoparticles in nanofertilizers are absorbed by the plant root and leaf surface, which are the main nutrient gateways of plant systems and are highly porous at the nanoscale. The application of a nanofertilizer can enhance the plant's nutrient uptake through these pores, or the process can facilitate complexation with molecular transporters or root exudates through the creation of new pores or by the exploitation of endocytosis or ion channels.
This results in enhanced nutrient uptake by the crops, meaning that a lower concentration of nanofertilizers are required for the same volume of crop yield.
Nanofertilizers: Controlled Nutrient Release
Using nanofertilizers instead of conventional fertilizers can also improve the stability and predictability of nutrient delivery. This is achieved by engineering the nanoparticles used in nanofertilizer so that they can release nutrients over long periods.
Several researchers have reported that the small size of nanoparticles used in nanofertilizers enables the absorption of abundant nutrient ions that is later desorbed slowly and steadily for an extended period. Therefore, formulations of nanofertilizers can provide balanced nutrition for crops throughout the growth cycle, improving agricultural production.
Nanofertilizers: Targeted Nutrient Delivery
Nanoparticles can also be engineered to target specific parts of the crop, enabling nanofertilizers to deliver the nutrients directly to the part of the plant where they are most needed. As a result, fewer nanofertilizers are required as less is wasted being delivered to the wrong part of the plant.
Nanofertilizers: Reduced Environmental Impact
Due to the reduced volume of nanofertilizers required to achieve the same or better crop yields than conventional fertilizes, the use of nanofertilizers reduces the environmental impact of agriculture. Using reduced volumes of fertilizer lessens the volume of harmful chemicals that the environment is exposed to. Therefore, nanofertilizers, to some extent, can help mitigate the negative impact of fertilizer use, such as damage to soil and water pollution caused by fertilizer run-off. While nanofertilizers are not inherently environmentally friendly, they may offer a less damaging alternative to the agricultural industry.
Nanofertilizers: Additional Benefits
Nanofertilizers can suppress crop diseases by acting directly on phytopathogens through various mechanisms, including the production of reactive oxygen species. These materials also enhance crop production indirectly by improving crop nutrition and boosting plant defense pathways.
In addition, the efficient use of nanofertilizers can improve crop productivity by enhancing the rate of seed germination, seedling growth and photosynthetic activity.
Finally, nanobiosensors that react with specific root exudates are also being explored. These techniques are relatively new and have numerous ethical and safety issues that must be carefully studied before implementation.
The Commercial Landscape of Nanofertilizers in Agriculture
The global agricultural landscape has radically changed since the revolution of green nanotechnology. Nanofertilizers are now being used in specific concentrations in accordance with the nutritional requirements of the crops, ensuring minimal differential losses.
There are three types of nanofertilizers: nanoscale fertilizers, nanoscale additive fertilizers, and nanoscale coating fertilizers.
Nanoscale fertilizers are made of nanoparticles that contain nutrients. Nanoscale additive fertilizers are traditional fertilizers with nanoscale additives. Nanoscale coating fertilizers are traditional fertilizers coated or loaded with nanoparticles.
The encapsulation of nutrients most commonly produces nanofertilizers with nanomaterials. Preliminary nanomaterials are produced using physical (top-down) and chemical (bottom-up) approaches.
More recently, the targeted nutrients are either encapsulated inside nanoporous materials, coated with a thin polymer film particle, or coated with emulsions of nanoscale dimension.
Encapsulation of beneficial microorganisms, such as bacteria or fungi, has shown promise as it can enhance the availability of nitrogen, phosphorus, and potassium in the root zone, thereby improving plant growth.
Nanofertilizers can also be classified based on their actions: control or slow-release fertilizers; control loss fertilizers; magnetic fertilizers or nanocomposite fertilizers (which use a nanodevice to supply a wide range of macronutrient and micronutrients in desirable concentration).
Porous nanomaterials significantly reduce nitrogen loss by regulating demand-based release and by enhancing the plant uptake process. Examples of porous nanomaterials include:
- Ammonium charged zeolites, which can enhance the solubility of phosphate minerals, showing an improvement in phosphorus availability and uptake by crops.
- Graphene oxide films, a carbon-based nanomaterial, can prolong potassium nitrate release, extending the time of function and minimizing losses by leaching.
- Nanocalcite (CaCO3-40%) with nano SiO2 (4%), MgO (1%), and Fe2O3 (1%) not only improve the uptake of calcium, magnesium and iron, but also notably enhance the intake of phosphorous with micronutrients zinc and manganese.
References and Further Reading
Adisa, I.O. et al. (2019) ‘Recent advances in Nano-enabled fertilizers and pesticides: A critical review of mechanisms of action’, Environmental Science: Nano, 6(7), pp. 2002–2030. doi:10.1039/c9en00265k.
Food Production Must Double by 2050 to Meet Demand from World’s Growing Population, Innovative Strategies Needed to Combat Hunger, Experts Tell Second Committee [online]. United Nations.
Shang, Y. et al. (2019) ‘Applications of nanotechnology in plant growth and Crop Protection: A Review’, Molecules, 24(14), p. 2558. doi:10.3390/molecules24142558.
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