Nanotechnology in agriculture
Research has shown nanoparticles to be a groundbreaking tool for tackling many arising global issues, the agricultural industry being no exception. In general, a nanoparticle is defined as any particle where one characteristic dimension is 100nm or less. Because of their unique size, these particles begin to exhibit properties that their larger counterparts may not. Due to their scale, quantum mechanical interactions become more important than classic mechanical forces, allowing for the prevalence of unique physical and chemical properties due to their extremely high surface-to-body ratio. Properties such as cation exchange capacity, enhanced diffusion, ion adsorption, and complexation are enhanced when operating at nanoscale.
This is primarily the consequence of a high proportion of atoms being present on the surface, with an increased proportion of sites operating at higher reactivities with respect to processes such as adsorption processes and electrochemical interactions. Nanoparticles are promising candidates for implementation in agriculture. Because many organic functions such as ion exchange and plant gene expression operate on small scales, nanomaterials offer a toolset that works at just the right scale to provide efficient, targeted delivery to living cells.
Current areas of focus of nanotechnology development in the agricultural industry include development of environmentally conscious nano fertilizers to provide efficient ion, and nutrient delivery into plant cells, and plant gene transformations to produce plants with desirable genes such as drought resistance and accelerated growth cycles.
Nanotechnology in agriculture has been gaining traction due to the limitations that traditional farming methods impose at both the scientific and policy level. Nanotechnology aims to address productivity and mitigate damage on local ecosystems. With the global population on the rise, it is necessary to make advancements in sustainable farming methods that generate higher yields in order to meet the rising food demand. Although there are seemingly numerous advantages in using nanotechnology in this sector, certain sustainability and ethical concerns around the topic cannot be ignored. The extent of their transport and interaction within their surrounding environments, as well as potential phytotoxicity and bioaccumulation of nanoparticles in food systems are not fully known. Ethical considerations also arise when we consider public discourse and regulatory challenges. The accessibility and affordability of nanotechnology-based agricultural solutions could disproportionately benefit large-scale industrial farms, potentially widening socioeconomic disparities with smallholder and Indigenous farmers. Experts emphasize the need for low-cost, scalable innovations that make these technologies accessible to diverse farming communities.
Chemical Properties of Nanomaterials in Agricultural Use
There are multiple properties of nanoparticles that make them effective and sought after for agricultural applications. Their small size, high surface area, and tunable surface chemistry allow for improved efficiency in nutrient delivery, pest control, and environmental remediation. A high surface-to-volume ratio allows for enhanced reactivity, solubility, and absorption, which are key to a thriving agricultural industry. These properties specifically allow for increased nutrient uptake & enhanced plant cell penetration.These nanomaterials can be made from a variety of chemical structures, with the most prominent being various metal oxides, carbon-based nanomaterials, and organic nanoparticles. Iron is an essential micronutrient, playing a role in chlorophyll synthesis, electron transport, and enzyme activation, and a deficiency can lead to reduced growth and crop yields. Iron oxide nanoparticles have been shown to improve seed germination, enhancing shoot and root development more than traditional iron supplements do. One example shows these particles increasing rice plant growth by enhancing iron bioavailability, as these nanoparticles are soil stable and penetrate root epidermal cells, ensuring sufficient nutrient transport to other parts of the plant. Other elements, such as silver and Copper, are becoming popular because of their antifungal and antimicrobial properties, making them useful in terms of disease and pest prevention. Specifically, the release of silver ions disrupts bacterial and fungal cell membranes that prevents diseases like powdery mildew, bacterial blight, and leaf spot. Nanoparticles can also be chemically modified to control properties like solubility. Chitosan or other polymer coatings have been shown to improve biodegradability and nutrient release, and one study shows Chitosan-coated zinc nanoparticles extend the release of zinc, reducing soil toxicity and preventing its over-accumulation in plants.
At the nanoscale, quantum confinement effects alter electronic, optical, and chemical properties, which allow nanomaterials to be tailored to specific agricultural applications, particularly in crop protection, light absorption, and antimicrobial activity. For example, silver nanoparticles are known to absorb UV light, a useful property for antimicrobial crop coatings. They can also scatter and reflect excess UV radiation, which has been shown to reduce sunburn damage to crops like tomatoes and grapes. Studies have also shown that silver nanoparticle sprays have reduced fungal infections in wheat crops while maintaining low toxicity to beneficial soil microbes. Zinc oxide nanoparticles have a wide bandgap of 3.37 eV, which allows them to regulate photosynthetic activity by enhancing light absorption and electron transport, as well as increasing chlorophyll content.
The environmental stability and degradability of these materials is a key component of what makes them so desirable for these applications. These properties are influenced by a variety of factors, including chemical composition, surface modification, and interactions with soil pH and organic matter. Understanding these interactions is crucial for noting pollution control and long-term environmental impact. As for chemical composition and solubility, metal-based particles can dissolve, releasing ions influencing soil and microbial activity, while carbon-based nanomaterials have been shown to absorb heavy metals from contaminated environments and resist degradation for much longer. Polymers such as chitosan or polyethylene glycol are used in coatings to increase water dispersion and prevent particle aggregation, while being selective with functional groups can enhance contaminant absorption. Nanoparticles can interact with substances like clay minerals, organic matter, and soil microbes, influencing their mobility and availability for plant uptake, while higher organic matter content enhances stability by reducing aggregation and sedimentation .
Soil remediation is one of the biggest sought-after benefits of utilizing nanoparticles in agriculture. The most promising materials include carbon-based nanomaterials and nano-clay materials, all of which exhibit high reactivity and selective adsorption capabilities. The molecular structure of graphene oxide and carbon nanotubes allows capture of metal ions due to high surface areas and strong absorption capacities. Activated carbon-based nanocomposites have been shown to remove up to 90% of heavy metal cadmium ions from water in a short time span of a few hours.
Nano-clay materials, such as montmorillonite-based nanoclays, trap pesticide residues, preventing them from leaching into water sources and maintaining soil fertility. By modifying their surface chemistry, nanoclays retain other harmful chemicals, mitigating impact on surrounding ecosystems. One practical application involves clay-polymer nanocomposites, which have been deployed in farmland runoff control to reduce pesticide and herbicide contamination, protecting nearby water bodies from exposure. These aforementioned properties are essential for agricultural applications—nanotechnology has been applied to create nanofertilizers, nanopesticides, and nanosensors, reducing excess waste, remediating soil conditions, and providing targeted nutrient uptake, reducing toxic conditions.
Categories and Agricultural Applications
Nanofertilizers
One area of active research in this field is the use of nanofertilizers. Because of the aforementioned special properties of nanoparticles, nanofertilizers can be tuned to have specialized delivery to plants. Conventional fertilizers can be dangerous to the environment because of the sheer amount of runoff that stems from their use. Having a detrimental effect on everything from water quality to air particulate matter, being able to negate runoff from agriculture is extremely important for improving quality of life around the world for millions. For example, runoff from sugar plantations in Florida has spawned the infamous algae bloom called "red tide" in water tributaries across the state, creating respiratory issues in humans and killing vital ecosystems for years.Nanofertilizers deliver nutrients more efficiently than conventional fertilizers by increasing plant bioavailability and reducing leaching into water systems, and their small-scale size allows them to pass through plant cell walls for nutrient transport. For example, silica nanoparticles bind to soil, allowing retention of essential root macronutrients and water retention such as Nitrogen, Phosphorus, and Potassium for longer periods of time.
Studies have shown that, in most cases, greater than 50% of the amount of fertilizer applied to soil is lost to the environment, in some cases up to 90%. As mentioned before, this poses extremely negative environmental implications, while also demonstrating the high waste associated with conventional fertilizers. On the other hand, nanofertilizers are able to amend this issue because of their high absorption efficiency into the targeted plant- which is owed to their remarkably high surface area to volume ratios. In a study done on the use of phosphorus nano-fertilizers, absorption efficiencies of up to 90.6% were achieved, making them a highly desirable fertilizer material. Another beneficial aspect of using nanofertilizers is the ability to provide slow release of nutrients into the plant over a 40-50 day time period, rather than the 4-10 day period of conventional fertilizers. This again proves to be beneficial economically, requiring less resources to be devoted to fertilizer transport, and less amount of total fertilizer needed.
As expected with greater ability for nutrient uptake, crops have been found to exhibit greater health when using nanofertilizers over conventional ones. One study analyzed the effect of a potato-specific nano fertilizer composed of a variety of elements including K, P, N, and Mg, in comparison to a control group using their conventional counterparts. The study found that the potato crop which used the nano-fertilizer had an increased crop yield in comparison to the control, as well as more efficient water use and agronomic efficiency, defined as units of yield increased per unit of nutrient applied. In addition, the study found that the nano fertilized potatoes had a higher nutrient content, such as increased starch and ascorbic acid content. Another study analyzed the use of iron-based nanofertilizers in black eyed peas, and determined that root stability increased dramatically in the use of nano fertilizer, as well as chlorophyll content in leaves, thus improving photosynthesis. A different study found that zinc nanofertilizers enhanced photosynthesis rate in maize crops, measured through soluble carbohydrate concentration, likely as a result of the role of zinc in the photosynthesis process.
Much work needs to be done in the future to make nanofertilizers a consistent, viable alternative to conventional fertilizers. Effective legislation needs to be drafted regulating the use of nanofertilizers, drafting standards for consistent quality and targeted release of nutrients. Further, more studies need to be done to understand the full benefits and potential downsides of nanofertilizers, to gain the full picture in approach of using nanotechnology to benefit agriculture in an ever-changing world.