Perspective Chapter: Application of Nanotechnology Solutions in Plants Fertilization and Environmental Remediation

Abstract

The effects of nanoparticles that are used on plants, either as foliar sprays or as fertilizers, vary between promoting and inhibiting. This effect varies according to many different factors, such as the type of nanoparticles, the concentration, the shape, the size, the type of plant, the soil characteristics, and the soil microorganisms. The effect of iron, zinc oxide, graphene, copper oxide, silicon, titanium, and carbon nanotubes on soil fertility, plant growth and development, and crop yield was discussed in detail. The nanoparticles affect the seed’s water absorption, roots, germination, stem, photosynthesis rate, photosynthetic pigments, and enzymatic and non-enzymatic compounds. Moreover, it also highlights the role of these particles in the different stresses that can be exposed to the plant and the mechanisms of tolerance of these stresses. This chapter presents the ability of these particles to combat pollution in its various forms, including groundwater, heavy metals, and wastewater. In addition, these nanoparticles accumulate in the water, soil, and plants, and impact humans and the food chain. Finally, the future prospects for the use of nanotechnology to achieve the goals of sustainable development.

1. Introduction

Nanotechnology can change agricultural systems and methods used via nanofertilization. It contributes to reducing pollution and protecting the environment, as well as reducing the costs of using chemical fertilizers. Nanofertilizers provide soluble nutrients that are quickly absorbed and reduce their build-up in the soil. In addition, it increases plant growth and development and enhances plant resistance to biotic and abiotic stresses. Nanofertilizers’ effect on plants varies according to the plant type, method of application, and the size and concentration of different nanoparticles. Moreover, to the positive effects of nanofertilizers, it is necessary to highlight their adverse effects related to toxicity. In addition, we will discuss the future prospects for the use of nanofertilizers.

2. Mechanisms of nanofertilizer impacts on soil, plants, crops, and stress

2.1 Soil fertility

A fertile soil is one of the fundamentals (along with water, climate, and seeds) that are essential for the advancement of agriculture and enhancing agricultural output efficiency. Several groups of researchers each suggested a creative approach to soil remediation. Advances in nanotechnology over the last century have allowed for a variety of approaches to increasing soil fertility. Unpredictably, NPs in soil may either inhibit plant development or promote it, depending on many factors related to nanoparticles and plants [1]. Several techniques, including spraying, pouring down nanofluid, and combining nanoparticles with the soil, are used to amend the soil with nanoparticles in order to increase soil fertility. Brownian motion and gravitational force may both play a role in the transit of NPs in soil, hence increasing the likelihood of these particles interacting with soil constituents that subsequently reflected plants [2]. If NPs are tiny enough (5 to 20 nm), they may penetrate plant cells through sieve-like cell walls [3]. This has enhanced the need for employing the substance in nanoform to overcome the problems in soil fertility and plant fertilization.

Several soil-beneficial processes are attributed to the use of nanomaterials, including the nitrogen cycle, the enhancement of enzyme activity, and the induction of plant-beneficial microbes. Numerous inorganic, organic, and composite nanomaterials were examined in terms of the possible influence they might have on fertilizing soil and resolving issues connected to plant development and production. These studies were conducted both in the laboratory and in the field, and they were evaluated and summarized in order to be a useful resource for farmers and researchers to save time and money.

One of the ways that nanoparticles are employed in agriculture is by incorporating them (in either fluid or solid form) into the soil [4]. These nanoparticles have the potential to introduce either on their own or in combination with conventional fertilization ingredients. In each of the aforementioned methods, nanoparticles and nanotechnology, in general, have the potential to provide solutions to soil problems that have preoccupied farmers over the period of the last several years. Among these solutions was the application of silver nanoparticles on the soil. The combination of these nanoparticles caused a rise in the number of diazotrophic bacteria in the soil, which is thought to have been a contributing factor in the elevated amount of fertilization seen in the soil. Moreover, iron nanoparticles, which are a component of a new generation of environmental remediation technology, may provide a cost-effective solution to one of the most challenging difficulties in environmental cleanup. Soil contaminants such as chlorinated organic compounds, toxic metals, and inorganic compounds can all be converted into less toxic or inert compounds by interacting with nanoparticles zero-valent iron [5, 6, 7, 8, 9]. On the other hand, it is shown that soil amendments containing metallic Cu NPs up to 600 mg/kg considerably improved the development of lettuce seedlings by up to 91% without causing any harmful consequences [1]. Recent research has shown that adding zinc nanoparticles to the soil as a kind of fertilizer considerably increases the amount of zinc that is available in the soil, which in turn significantly increases the amount of zinc that is present in the plant’s shoots and grain. This is due to that the application of these fertilizers considerably accelerated the development of plant roots and exudates. These exudates have the potential to greatly boost both the availability of zinc and its absorption by plants [10, 11].

One of the most promising approaches that deliver the answer to reducing soil toxicity is the use of nanocomposites, which will eventually result in an improvement in plant growth and production [12]. The higher surface-to-volume ratio of graphene oxide (GO) nanoparticles has unique capabilities as an efficient water transporter in soil because of its sp2 and sp3 hybrid structure; these particles could contribute to solving drought problems and the lack of water [13]. CuO nanoparticles, on the other hand, promote the growth of plant growth-promoting microorganisms in the rhizosphere of Salvia miltiorrhiza (red sage) [14, 15]. The ameliorating potential of Si nanoparticles for soil is well known since these nanoparticles are often more effective than their bulk equivalents [12, 16, 17, 18, 19, 20, 21]. Due to the stimulation of plant photosynthesis by SiO₂ nanoparticles, silicon plays a critical role in improving the plant antioxidant system’s efficiency, promoting plant growth under salt stress, and increasing the plant’s tolerance to abiotic and biotic stressors. Therefore, SiO₂ nanoparticles provide excellent solutions for enhancing the capabilities of the soil to support agricultural activities [12, 22]. TiO₂ nanoparticles have several uses in agroecosystems due to their attractive physical and chemical characteristics, availability, cheap cost, and excellent stability. TiO₂ NPs are used in nanofertilizers and nanopesticides to increase soil fertility and crop development as well as improved light retention [23, 24, 25]. Numerous studies show that TiO₂ nanoparticles, at a specific concentration range in various plant species, may increase plants’ resistance to cold, heat, drought, NaCl, and ultraviolet light [26, 27, 28, 29, 30, 31]. TiO₂ NPs stimulate soil nutrients and microbial dynamics at low concentrations [32]. Nanoparticles of titanium dioxide make it easier for seeds to absorb water and, as a result, accelerate the germination process [12]. The radicle, plumule, root, and seed germination of canola seedlings is accelerated by the application of TiO₂ NPs [33].

Carbon nanotubes are employed as fertilizer to enrich the soil, consequently encouraging the growth of many plants, including tomatoes, cucumbers, rice, maize, broccoli, and soybeans [3, 34, 35, 36, 37, 38, 39]. Carbon nanoparticles have the ability to restrict the mobility of herbicides in agricultural applications. Furthermore, CNPs improve plant photosynthesis, crop development, water absorption, antioxidant levels, and the efficiency of nitrogen (N), P, and K use. CNPs have recently reported as part of a novel approach that also includes compost, mycorrhizal, and arbuscular fungi blended into the soil. This combination of CNPs has the ability to protect plants against drought stress. The innovative use of CNPs in agriculture might fulfill growing food demand while simultaneously protecting the environment [40]. The recent approach is a significant indicator that nanotechnology is a fertile field for agricultural research, and many more studies will be required to develop innovative agricultural solutions in the near future.

2.2 Plant growth and development

The use of nanotechnology in agricultural sciences, with the assistance of nanoscience, is now achieving a high level of success, resulting in the development of novel solutions in a wide range of agricultural domains. The consequences of all the novel approaches to enhance soil, irrigation water, and agricultural climate discovered via the usage of nanotechnology are indirectly improving plant components in order to produce agricultural items and boost yields. For example, the addition of iron nanoparticles to the soil reduces soil contaminants such as chlorinated organic compounds, toxic metals, and inorganic compounds that could harm plants. A wide variety of nanoscale materials were prepared and analyzed to provide a fresh strategy for addressing agriculture’s perennial challenges. These nanoparticles are often delivered directly to plants through the seeds, stems, or leaves in order to improve growth and agricultural productivity. In this section, all of the recent researches on how nanoparticles affect plant development are summarized.

Using carbon-based nanomaterials (CNTs) boosted seed water absorption by moving it from the seed coat to shoots and leaves [1]. This improved germination percentage and plant growth by maximizing water uptake and nutrient intake [41]. This technique has been used to improve seed germination, root and plant growth, and final growth in numerous crops, including hybrid Bt cotton, Phaseolus mungo L., Brassica juncea L., tomato (Lycopersicon esculentum Mill) and rice (Oryza sativa L.), resulting in an increase in biomass and seed germination [12]. CNTs have a crucial role in stimulating rice seedling growth, root elongation, and seed germination in zucchini species [42]. In addition, CNTs improved seed germination, vegetative biomass, and tomato growth [43], and multi-walled carbon nanotubes (MWCNT) influenced the fresh and dried mass of tomato roots as well as gene expression [44]. Research demonstrates that maize, tobacco, switchgrass, rice, tomato cell cultures, barley, wheat, and soybean seeds grew faster when treated with single-walled carbon nanohorns (SWCNHs) [12]. In fact, the effect on plant shape depends on the type of nanoparticles and its applied [45]. However, titanium dioxides (TiO₂) NPs, such as Ag and graphene NPs, have shown to improve seed germination by increasing the ability of internal tissues to convey water and increasing the metabolism of seed stores [24]. They also improve water absorption, which accelerates seed germination [12]. Increased nitrate absorption and photosynthetic rate attributed to the augmentation of nitrogen metabolism caused by the introduction of TiO₂ NPs in spinach, showing that these nanoparticles may really boost plant growth [44]. The application of TiO₂ NPs to canola seedling plants increased the growth of the radicle and plumule, as well as root and seed germination [33].

Nanoscale zinc oxide (ZnO) is essential for plant growth at low concentrations and does not inhibit onion seedling growth or cell division [33]. ZnO NPs enhanced the germination of soybean, wheat, tomato, and onion seeds [46] and increased the germination of cucumber seeds by 10%. In addition, ZnO NPs with a particle size of 50 nm favorably influenced the roots of rapeseed [33]. In addition, ZnO NPs application on the coffee plants had a positive effect by increasing the fresh weight of roots (37%) [44]. Compared to the control, ZnO NPs at 10 mg/L accelerated seed germination (100%), root length (185 mm), and root width (0.5 mm) [47].

Similar to other nanomaterials, silver nanoparticles (SNPs) had beneficial impacts on vascular plants, including seed germination, root development, and plant biomass. These benefits correlated with the concentration and structure of SNPs [42]. Experiments conducted with varied concentrations of SNPs on Cucurbita Pepo revealed a notable change in seeding speed and duration due to the presence of the SNPs [48]. SNPs greatly improved wheat seeding rate, rootletlet and plumule length, and rootletlet and plumule wet and dry weight [49]. In fenugreek plants, low concentrations of SNPs (10–20 g/mL) increased seedling growth and seed germination [44]. A number of investigations on the impact of SNPs on two wheat and barley types found a rise in germination ratio stem, length, and a decrease in root length compared to the control [50].

Rice seed germination is stimulated by the addition of Silicon (Si) NPs. Si NPs increase maize seed germination by improving nutrient availability [41]. Si NPs enhanced all seedling parameters such as percent germination, germination rate, length, and fresh and dry mass of root and shoot in Changbai larch (Larix olgensis Henry) seedlings [51, 52]. Also, utilizing Si NPs for pre-chilling seeds in tall wheatgrass (Thinopyrum intermedium L.) breaks inertia, stimulates seed germination, and boosts the vigor index, mean germination time, and dry weight of seedling roots and shoots [50]. Soybean (Glycine max L.) germination and growth are boosted by boosting nitrate reductase activity and improving the seeds’ capacity to absorb and use water and nutrients [51, 52]. Seed germination, plant height, and root and shoot dry weights were all improved by using Si-NPs in rice (Oryza sativa L.) seedlings [53]. In a similar manner, Se NPs stimulated organogenesis and accelerated root development in Nicotiana tabacum L. by up to 40%, compared to the effect of aqueous selenate [33]. Gold nanoparticles (NPs) at concentrations of 5–15 mg/L considerably enhanced the germination and physiology of older maize seeds without causing any harm [54].

Numerous researchers have used a wide number of techniques, including the biological approach, in order to fabricate NPs with a wide range of morphologies and sizes [48, 51, 52, 54, 55, 56, 57]. The biological approach is a synthetic technology that involves the extraction of plant components for use in the nanoparticle synthesis process. This technology has the potential to be an effective solution in agricultural applications since it is controllable, inexpensive, low-risk, and safe. Generally, nanotechnology has the potential to improve agriculture’s sustainability and benefits, but there are still many questions surrounding its use in this field.

2.3 The effect of nanofertilizer on crop yield

Numerous studies outline the nanotechnology mechanism for crop enhancement. In this part, these findings on the function of nanotechnology in crop improvement are discussed. Nanotechnologies have the potential to generate a substantial increase in agricultural productivity as well as enhancements to food production systems [58]. Nanotechnology is one example of a technology that may aid in agricultural production by reducing wasteful input consumption and increasing productivity. Nanotechnology is regarded as an effective tool for managing a wide range of environmental stresses by providing novel and practical solutions. Nano-fertilizers (NFs) considerably increase plant growth efficiency, soil quality, and crop yield of high-quality fruits and cereals [59], and also, may serve as a sustainable strategy to promote agricultural yield in (semi-) arid regions [60]. NFs have the potential to improve nutrient absorption and plant output by modulating fertilizer availability in the rhizosphere, prolong stress tolerance by enhancing nutritional capacity, and raise plant defense mechanisms. For sustainable agriculture, NFs might potentially take the place of synthetic fertilizers since they are better at stimulating plant growth [61]. The applications of nanoparticles and nanomaterials have a positive effect on crop productivity via different strategies. It is summarized by green synthesis of nanoparticles, plant-targeted protection via the application of nanoherbicides and nanofungicides, precise and constant supply of nutrients through nanofertilizers as well as tolerance to abiotic stress, by several mechanisms such as activation of the antioxidant enzyme system that alleviates oxidative stress [62]. In addition, the tolerance to abiotic stress by several mechanisms, such as activation of the antioxidant enzyme system that alleviates oxidative stress is one of the positive impacts of the applications of nanoparticles and nanomaterials in agriculture. All the mentioned positive effects could be due to their nano-size properties, their high nutrient use efficiency, their slow release of nutrients, and the controllable necessary dosage of nanomaterials used in fertilizer to get the desired results [63].

In the most recent decades, there have been reports that nanoscale zero-valent iron has the ability to increase plant development in the laboratory. Therefore, nanoprimed seeds demonstrated superior crop performance when compared to hydroprimed seeds in the conventional sense. As a result, nZVI is classified as a “pro-fertilizer,” and it is utilized commercially as a seed treatment agent capable of increasing plant development and yield while causing little disruption to the soil ecology [64].

Essential oil content was found to increase with the use of nano-iron fertilizer, fruit output and quality were both enhanced with the use of nano-zinc and boron fertilizers, and the use of nano-zeolite was shown to increase germination rates and prolong the life of soil nutrients. Increased growth from nanoparticles helps crops mature sooner and recover more quickly from environmental challenges. In addition to increasing the levels of photosynthetic pigments and osmolytes, the synthesized Fe₂O₃ NPs also increased the activities of the enzymes peroxidase (POD), polyphenol oxidase (PPO), catalase (CAT), and superoxide dismutase (SOD) in healthy as well as infected tomato plants when compared with the control. The optimum therapy for peroxidase and polyphenol oxidase activities was determined to be the administration of Fe₂O₃ NPs (10 g/mL) to stress plants, which enhanced the activities of POD by 34.4% and PPO by 31.24%. On the other hand, the best treatment for stressed plants was to apply Fe₂O₃ NPs (20 g/mL), which increased the activities of CAT by 30.9% and SOD by 31.33%) [65]. When compared to the control, the same treatment had significantly higher biological yield, grain yield, protein yield, and harvest index, with 14.792 Meg/ha, 7.100 Meg/ha, 890.34 kg/ha, and 40.00 percent, respectively [66]. Under normal circumstances, applying ZnO NPs led to considerable growth and biomass augmentation while preventing drought-induced decrease. ZnO NPs treatment increased photosynthetic pigments, photosynthesis, and PSII activity, with peak values at 100 mg/L [67]. Under both normal and drought circumstances, ZnO NPs caused an increase in the total amount of proline, glycine betaine, free amino acids, and carbohydrates. In addition, foliar application of ZnO NPs was shown to be effective in preventing the drought-induced decrease in the amount of phenol and mineral nutrients [67]. Stimulatory effects were seen on total chlorophyll (0.93 g/kg FW), shoot biomass (2168 kg/ha), and essential oil content (3.4 g/kg) and yield (7.4 kg/ha) as a result of sub-risky levels of Zn in nanoform absorption (amounted to an average of 152.6 mg Zn/kg after foliar application of 160 mg of zinc oxide nanoparticles) in comparison with ZnS treatment or control. Foliar application of 160 mg/L ZnO NPs is recommended for optimal micronutrient Zn biofortification, biomass production, and essential oil yield in dragonhead [60]. The researchers used many nanocomposites with different concentrations on different plant species to study their effect on their production and increase the yield [4].

Foliar application of nanoparticles enhanced the foliar nutrient status and crop growth and yield. The nano-enabled foliar application could be an ideal strategy for advancing agricultural productivity. Canola plants had an increase in their biomass after receiving a foliar spray of Ca-NPs at a concentration of 100 mg/L, which was deemed the best dosage. Canola plants had an increase in their biomass after receiving a foliar spray of calcium nanoparticles at a concentration of 100 mg/L, which was deemed the best dosage. Furthermore, Ca-NPs also induced a drought-tolerant response in Brassica napus plants, which correlated with an uptick in the expression of key antioxidative defense enzymes (APX, POD, SOD, CAT), secondary metabolites and non-enzymatic components (protease, lipoxygenase, proline, total soluble protein contents, endogenous hormonal biosynthesis) [68]. Grain yield components such as the number of pods per plant and 100-grain weight were also affected by seed priming with nano-Zn. Nano-Zn priming increased grain protein percentage by 21%. Therefore, to increase the yield of white beans, priming treatment with nano-Zn as well as foliar application of zinc + iron can be used [69].

The results demonstrated that nano-K₂SO₄ enhanced shoot dry weight, plant height, number of flowers, number of tillers, root length, root fresh weight, and root dry weight under both salt levels on two alfalfa (Medicago sativa L.) genotypes [70].

Currently, the use of nanoparticles is having an impact on agricultural production. There is evidence that the results obtained indicated that the foliar application of CuNPs improved the physical and nutraceutical quality and the concentration of Cu in melon fruits. The highest weight and the best diameters of the fruit were obtained with copper nanoparticles have a strong impact on the growth and development of different crops. Biofortification specifically with Cu NPs improves the nutritional quality of food and its consumption has a positive influence on the health of humanity. The findings indicate that there is a statistically significant relationship between the copper nanoparticles and the phytochemical variables found in melon fruits. It was determined that the use of Cu NPs may be an option to enrich melon fruits, and it has the potential to alleviate the problem of copper insufficiency in the diet of the general population [71].

Nano-fertilizers suggest new crop management strategies. Although potassium (K) is difficult to incorporate into organic materials, it helps to increase rice crop quality [72]. Although the dosage of 200 ppm of K nanofertilizer resulted in a greater increase in yield, the dosage of 100 ppm produced greater accumulations of biomass, total chlorophyll content, SPAD values, photosynthetic activity, and nitrate reductase activity. Based on the findings obtained, it seems that the use of K nanofertilizers has a positive impact on the physiological growth of plants [73]. Drip irrigation with 75% nN and foliar treatment with 25% nN have a substantial effect on growth and biochemical parameters [74].

Plant species vary in the efficiency of nanoparticle absorption and the impact of nanoparticles on growth and metabolic processes. Nanoparticle concentration influences activities such as germination and plant growth and development [66].

Various kinds of nanomaterials have shown great promise in promoting sustainable agriculture as they help to improve agricultural production by increasing the efficiency of inputs and minimizing yield losses. Nanomaterials offer a wider specific surface area to fertilizers [75].

Our most significant findings are as follows: (1) Plants have the ability to take up nanomaterials via their roots and leaves, which will then subsequently be transformed by the plant. (2) Plant growth may be stimulated and stress alleviated with moderate applications, while high concentrations can be harmful. (3) It is impossible to ignore the impact that nanomaterials have on the rhizosphere [76].

Using nanofertilizers is a potential strategy that may boost the sustainability and efficiency of the agricultural output of farmed crops. This technology is also effective. This technology is also successful due to its nano-size features, high nutrient usage efficiency, gradual release of nutrients, and therefore low necessary applied dosage of fertilizer [77].

Smart fertilizer means using smart agro-technological and advanced tools for the control dose and time of applied fertilizers such as global positioning systems, and remote sensing. These tools are able to minimize agrochemical inputs and maximize crop yield [63].

Nano-fertilization is considered an emerging strategy for increasing plant production while avoiding agroecosystem contamination.

One way to boost agricultural efficiency is the use of nanotechnology. At present, numerous novel nanomaterials are commercially used in agriculture and developed to improve crop productivity and preserve food quality and safety [78].

2.4 The relationship between nanofertilizer and stresses

Many scientists have studied the effect of factors that threaten crop production, including water stress, salinity, and alkalinity, among others. Nanotechnology is a promising tool for increasing crop yields and improving plant stress tolerance. Many books and chapters talk about one or more types of stress. Among them, for example, is a book, Nanomaterial Interactions with Plant Cellular Mechanisms and Macromolecules and Agricultural Implications, and accordingly we tried to start from where the others ended, as we limited ourselves to presenting some research that was published in 2022 and beyond.

Table 1 shows the type of stresses as well as the impact of nanoparticles by different concentrations on the growth and development of various plants.

Stresses	Plant	Nanoparticles	Concentration	Applications	Reference
Salinity	Pea (Pisum sativum L.)	Si and NSi	3 mM	Enhanced the following indications as vegetative growth, relative water content (RWC), plant height, fresh dry weight, total yield, antioxidant defense systems, and K^+ content in roots and shoots	[79]
	Rice (Oryza sativa L.)	ZnO-NPs	50 mg/L	Root length, root fresh weight, root dry weight, root K^+ content, and root antioxidant enzymatic activity were all enhanced by applying 50 mg/L ZnO-NPs often in salinity as well as improved the K^+/Na^+ ratio in the rice’s root system.	[80]
	Squash (Cucurbita pepo L.)	Fertilizer (nano-K)	0.50 g/L nano-K	Using nano-K to promote antioxidant and photo-synthetic machinery, minimize oxidative stress biomarkers and Na^+ levels, boost tolerance to salt stress, and improve squash yield and yield quality under salt stress.	[81]
	Spearmint (Mentha spicata L.)	Chitosan-melatonin nanoparticles (CTS-HPMC-Mel NPs)	an chemical priming agent	Adverse effects of salt stress were ameliorated with Mel and CTS-HPMC-Mel NP treatments by enhancing morphological traits, proline, antioxidant enzymatic activities, as well as the content of dominant constituents of essential oil profile. Engineered CTS-HPMC-Mel NPs could be applied as an innovative protective agent to mitigate the effects of salinity in crop plants.	[82]
Drought	Rice (Oryza sativa L.)	ZnONPs	25 ppm	increase both of plant height, total chlorophyll contents, plant fresh and dry weights as well as seed, straw yield and the 1000 paddy weight of rice plants	[83]
	Wheat (Triticum aestivum L.)	Iron nanoparticles 10 mg/L when combined with Glomus in- traradices	10 mg/L when combined with Glo-musint-raradices	Iron nanoparticles combined with Glomus intraradices promoted significantly the growth and drought-tolerant of wheat	[84]
	Corn (Zea mays L.)	(CNPs)	4.5, 10 nm	Increase in their anti-oxidant defense system.	[40]
	Peppermint (Mentha piperita L.)	Myco-Root + TiO2 NPs	100 mg/L	The maximum content of menthol, 1,8-cineole, and neo-menthol was obtained under mild drought stress (I40) fertilized with Myco-Root + TiO2 NPs.	[85]
Potentially toxic elements (PTEs)	Barley (Hordeum vulgare L.)	nano-Fe2O3	1% (w/w)	Lower inhibitory effects on biometric parameters as well as lowering PTEs-induced oxidative damage and protect the growth of barley plants under contaminated soils.	[86]
Cd stress	alfalfa supplemented (Medicago sativa)	nZnO	Soil application of 90 mg/kg nZnO with BC (2%)	Decreased Cd and increased Zn-bioaccumulation into roots and shoots as well as higher nZnO and BC levels efficiently alleviated the Cd-mediated reductions in alfalfa biomass, anti-oxidant enzymatic response, and gaseous exchange traits than control.	[87]
Soils contaminated with rare earth elements (REEs)	Duckweed (Lemna minor)	nano terbium (Tb)	less than 100 mg/L	Increased the contents of (N), (P), (K^+), (Ca^+2), (Mg^+2), (Mn^+2) and (Fe^+2)	[88]
CeO2	Pakchoi (Brassica chinensis L.)	CeO2 NPs	0.7 mg/kg	Sub-stomatal CO2 was increased dramatically under low doses of CeO2 NPs	[89]
Cu stress	Rape (Brassica napus L.)	SNPs	5 mg/L	SNPs application enhanced the shoot height, root length, and dry weight of shoot and root by 34.6%, 282%, 41.7% and 37.1%, respectively, over Cu treatment alone SNPs application has the sustainable technology for increasing plant productivity and reducing the accumulation of toxic metals in heavy metal-polluted soils.	[90]

Table 1.

The various impacts of different types of stresses with different concentrations on growth and development of plants.

3. The role of nanofertilizer in environmental protect

The essential key to agricultural sustainability is to perform all farming activities in a sustainable manner [91]. The agricultural sector is facing a series of biological and environmental challenges [92]. Therefore, it is essential to manage the available natural resources in a sustainable method [93]. This requires finding more creative and innovative solutions using modern technology such as nanotechnology that can provide society with the proper technologies used in environmental detection, sensing, and remediation [94]. Farmers face several challenges in traditional agriculture. There are no fertilizers can successfully provide optimal plant nutrients. In addition, chemical toxicity results from the high use of fungicides/pesticides/herbicides [95]. The chemical soluble fertilizers used not only have less utilization efficiency (less than 30%) but large amounts of these are also lost during the application causing environmental pollution [96].

The use of nanoparticles would decrease the consumption of agrochemicals due to the very high efficiency. The environmental benefit of using nanoparticles is more known when it starts to be used, for example, in plant protection products, chemical copper could be replaced with a suitable Cu-NP which is the least environmentally harmful [97]. Likewise, the seed soaking with nanoparticles solution has shown improvements toward increased and more stable production [98]. In order to use nanoparticles in a clear legislative framework, it is necessary to synthesize them with an innovative composition as well as similar in their properties as much as possible to natural substances [99]. In this context, nanofertilizers synthesized by the bio-method are promising substances for achieving sustainable growth of crop yields and securing food for the ever-increasing population [79].

The soil is a system full of life, particularly symbiotic associations with the roots of different plant species [99]. Plants exchange gas and fluid with the environment via their leaves and roots, where rhizosphere microorganisms (rhizobacteria and mycorrhizal fungi) solubilize minerals and then the plants absorb solubilize nutrients [100]. This can reflect on the germination of seeds, root and shoot development, biomass, and yield of the crops [101].

Nanofertilizers have some characteristics compared to conventional fertilizers [99]. These features help crops absorb nutrients slowly and sustainably due to a high surface-to-volume ratio and reduced loss of nutrients [102]. Also, it is having active sites for a more significant number of biological activities, which increases the efficiency of plant absorption of nanofertilizer [103]. Furthermore, soil fertility improvement as well as maintaining a suitable environment for the growth of microorganisms in the soil [104]. Thus, it is providing sustainable solutions to environmental pollution and climate change [105].

Methods for preparing nanoparticles vary to the available capabilities and the purpose of the application [106]. Many of the protocols relied on eco-friendly, less polluting, more sustainable approaches [107]. Also, it can use extraction and separation strategies away from pressures [108], high temperatures [109], acidifications [110], and toxic metals [111]. The most natural sources used to synthesize nanoparticles from plant extracts as well as microorganisms such as yeasts, fungi, bacteria, and algae. Biomolecules of cells microorganisms and plants such as enzymes, amines, proteins, phenolic, alkaloids, and pigments contribute to synthesizing NPs and capping of them [112].

Bioremediation provides based on nanomaterials many features compared to conventional treatments. It has exhibited a quantum effect with decreased activation energy as well as contact with a larger amount of it with the surrounding materials, and also, has a high competence level, selective to specific metals, and is more economically feasible [113].

Bioremediation processes were used in groundwater and wastewater management, uranium remediation, solid waste, soil remediation and remediation of heavy metal pollution as well as petroleum [114]. The ability of NMs to combat pollution is a revolutionary change in the ecological field. Furthermore, it can mention these changes via some examples such as the nanoscale zero-valent iron removing AS (III) in anoxic groundwater [115]. Eliminating hydrophobic contaminants was via using engineered polymeric NPs [116]. Formatting special structures of PAMAM dendrimers are used in water treatment [117]. Employment-engineered polymeric NPs are used for soil remediation [118].

On other hand, NPS have a great effect on biodegradation especially dye contaminants. These dyes have high chemical stability, and compositions complicated and long-distance stability in running water, which will lead to inhibited photosynthesis, the development of aquatic biota and less use of dissolved oxygen as well as decreased watercourse recovery rate Figure 1 [119].

Figure 1.

Graphic representation of the advantages of nanotechnology in bioremediation.

In addition, several studies showed the importance of zinc oxide (ZnO) and titanium dioxide (TiO₂) in environmental remediation which were used in dye-sensitized solar cells as well as water photoelectrolysis [120].

NPs have the best-advanced strategies for the treatment of wastewater due to their properties such as high adsorption and reaction capacities as well as a suspension in aqueous solutions as colloids, less time-consuming, efficient cost-effective, eco-friendly and less waste compared with conventional methods [121].

Green nanomaterials have a wide effective of abilities to remove organic and inorganic solutes, toxic metal ions and pathogenic microorganisms from water by using various nanomaterials such as nanosorbents (carbon-based nanosorbents such as Captymer™), nanostructured catalytic membranes (cellulose acetate, polyvinylidene fluoride, chitosan and polysulfone), nanocatalysts (silver nanocatalysts), bioactiveNPs, molecularly imprinted polymers (MIPs) and biomimetic membranes [122, 123].

4. Nanofertilizer toxicity

NPs found naturally in soil via agricultural activities or rain as well as through anthropogenic production [124]. Also, it is more concentrated in soil compared to air and water. Plants absorb these NPs from the soil and move them to reach various parts of plants and finally, a human consumes this plant Figure 2 [125].

Figure 2.

Graphic representation of the environmental benefit for nanoparticles fertilizer.

The NPs’ increasing application in agriculture led to directly interacting with the environment as well as harmful effects on aquatic, terrestrial species and humans [105]. It is reflected in the accumulation of NPs in the soil, fertility and physicochemical characteristics of the soil [126].

The NPs’ harmful effects on plants include DNA damage, reactive oxygen species (ROS) formation, association with nuclear protein, chromosomal aberration, decreased DNA repair and genetic defects. NiO NPs access the DNA of tomato plants and produced irreversible cell damage [127, 128]. Application Co₃O₄ NPs in eggplants caused apoptosis in their cells [128]. In addition, using ZnO NPs led to adverse effects on membrane integrity, chromosomal damage and DNA strand breakage in Vicia faba L., Nicotiana tabacum L. and Allium cepa L. [129, 130].

The presence of silver NPs in the range of 0.1–0.5 mg kg − 1 in soil inhibits the growth of dehydrogenase activity of bacteria [131].

Likewise, CNTs, copper NPs, zinc NPs and iron NPs have several adverse effects on soil microflora and aquatic life, which include aquatic microbes, vertebrates and aquatic plants [132, 133]. It is reported [134] that graphene oxide NPs caused toxic effects on freshwater algae due to the generation of oxidative stress.

5. Conclusion and future perspective

Sustainable development to achieve the Zero Hunger SDG 2030 should be inclusive. This goal is achieved via the implementation of agricultural practices to ensure improved crop production, protecting the natural resources (water, land and forests) as well without adverse impacts on biota and human beings [105].

Nanotechnology can achieve these requirements by relying on vital nanomaterials in environmental remediation and other industries. It is cost effective and involves less toxic waste disposal. Also, it improves catalytic efficiency and selectivity.

Despite the fact that the reports that are readily available on the application of nanoparticles to the process of cultivating soil and plants are only for a small number of nanomaterial, the quantity of materials used in agriculture is significantly greater than what is currently available.

As a result of this, there is an urgent need to implement a bigger variety of nanomaterials, each of which must be manufactured using a new precursor and creative synthesized methods. In addition, using plant components in the manufacturing of nanoparticles during green synthesis may result in the development of nanoparticles that are well suited for performing effectively as nanofilters.

However, the growing application of NPs must be a concern on some points, their accumulation in the soil, their interaction with plants and microorganisms and the dose of application as well as toxicological aspects in ecotoxicological and food chains.

The potential impact of nanofertilizers on human health necessitates more investigation into their persistence in plant tissue that is consumed. While nanofertilizers have the potential to radically alter farming methods, it is essential to evaluate their effects on the environment as soon as possible.

Therefore, our insight will concern the development of green strategies for biogenic nanoparticle synthesis, examining plant/soil–NP interactions in the field in a way that enhances crop productivity and provides a suitable environment for the growth and development of all living organisms and feeding future generations with healthy food.