Ikunda Herman Massawe
Ernest Mbega†
Akida I. Meya- The School of Life Science and Bio-Engineering, Nelson Mandela African Institution of Science and Technology (NM-AIST), Arusha, Tanzania
Introduction: Nanoparticles and Plant Growth-Promoting Microbes are trending as sustainable means for supplying plant nutrients. The purpose of this review was to understand how these technologies have been applied together to enhance plant growth.
Methods: A PRISMA protocol was followed to explore relevant articles that reported the impact of nanoparticles on plant growth-promoting microbes or their influence on plant growth. By using the established search string, 70 original research articles published between 2000 and 2023 from Google Scholar and Scopus were obtained.
Results: The results show that 21 microbe genera with more than 50 species can promote plant growth. Free-living plant growth-promoting rhizobacteria are the most studied microbes, followed by arbuscular mycorrhizal fungi. Inorganic nanoparticles, such as ZnO, are the most extensively studied nanoparticles, followed by organic nanoparticles, primarily chitosan.
Discussion: Nanoparticles and plant growth-promoting microbes can be applied as separate treatments or by formulating nano-biofertilizer, and their combination ameliorates biotic and abiotic plant growth stresses. The effect of nanoparticles on plant growth-promoting microbes is concentration and species-dependent.
Graphical Abstract.
1 Introduction
Sustainable agriculture is a priority in the current agricultural production systems, while increasing agricultural production remains to be a core focus to ensure world food demand is met (FAO, 2021; Marambe and Silva, 2012). It is undoubtedly right to say there is a need to ensure both aspects are achieved. It is argued that mineral fertilizers play a vital role in agricultural production as they contribute up to 40% of the productivity (Elizabath, 2019). On the contrary, inappropriate usage of mineral fertilizer is the major contributor of environmental pollution, such as air pollution, water pollution, soil nutrients depletion, and increased emissions of greenhouse gases in agricultural systems (Kumar et al., 2019). Therefore, there is a need to think of sustainable means of managing and supplying nutrients to plants. Plant growth-promoting microbe (PGPM) and nanoparticles (NPS) are some of the important sustainable ways for supplying plant nutrients and promoting plant growth. In this review, these two important game-changing aspects for sustainable plant nutrient supply and management are explored.
PGPMs have been extensively studied in agricultural systems and have proven to have positive functions as far as nutrient supply and plant growth are concerned (Dhawi, 2023). PGPMs are divided into three groups, namely: arbuscular mycorrhizal fungi (AMF), plant growth-promoting rhizobacteria (PGPR), and rhizobia. PGPR are free-living rhizobacteria that promote plant growth by colonizing the roots’ rhizosphere without forming any association with the plant, e.g., Pseudomonas spp., Azospirillum spp., Azotobacter spp., Bacillus spp., Burkholderia spp., and Enterobacter spp. (Jeyanthi and Kanimozhi, 2018; Lucy et al., 2004; Rai et al., 2018). AMF are symbiotic fungi that penetrate the cortical cells of plant roots, forming unique tree-like structures called arbuscules, e.g., Rhizophagus spp. and Glomus spp. (Kumar et al., 2022). PGPM promotes plant growth through mechanisms such as the production of phytohormones like Indole Acetic Acid (IAA), ethylene, cytokinin, and Abscisic Acid (ABA) that enable cell elongation, division, and expansion (Kumar et al., 2022). Also, these microbes are involved in N fixation and solubilization of P, K, and Zn, thus improving nutrient availability and supply (Rai et al., 2023a; Rai et al., 2023b; Singh, 2013). Other functions of PGPM include Phytoremediation, improvement of plant resistance to biotic and abiotic stresses such as soil salinity and drought (Ma et al., 2020; Singh, 2013). Application of PGPM in agriculture offers an alternative, sustainable means for plant nutrient supply and brightens the future of sustainable crop production (Singh, 2013).
One of the promising applications of nanotechnology in agriculture is the formulation of nano fertilizers to address crop nutrition issues. Nano fertilizers are said to be an excellent replacement for bulk soluble fertilizers as they help in the slow release of nutrients, thereby improving nutrient use efficiency and reducing risks of environmental pollution (Elizabath, 2019). The major aspect of nanotechnology is the utilization of nanostructured molecules or atoms (nanoparticles) over the normal bulk materials. Examples of these nanoparticles (NPs) include Mesoporous silica NPs, Carbon nanotubes, Liposomes, Quantum dots, Metallic NPs such as selenium NPs, and Metal oxide NPs such as ZnO and TiO2 (Mayurakshee et al., 2023; Rai et al., 2023a; Rai et al., 2023b). Nanoparticles can be used as (i) a source of plant nutrients when they are applied as they are, (ii) a means of delivery of nutrients to plants to ensure targeted uptake, and/or (iii) a coating to protect nutrient fertilizer and ensure a slow release of nutrients. In whichever way they are used, NPs offer a sustainable means of nutrient supply to the plants and help in protecting the environment from the adverse effects of mineral fertilizers (Elizabath, 2019). NPs are meant to reduce the quantity of fertiliser resources used, lessen nutrient loss, and improve crop quality and the overall yield (Mayurakshee et al., 2023).
Nanotechnology and biofertilizers can be integrated to form nanobiofertilizer with increased efficiency, stability, and functionality of PGPMs, thereby improving nutrient use efficiency, reducing nutrient losses, and increasing crop yield (Rai et al., 2023a; Rai et al., 2023b; Yadav and Yadav, 2024). This integration involves an encapsulation process where bacterial cells of PGPMs are coated with NPs, thereby protecting them from harsh environmental conditions, extending their shelf life, and enabling their gradual release (Oyediran et al., 2025). The main objective of this review is to explore the potential of applying nanotechnology in formulating biofertilizers for promoting plant growth as a sustainable way of enhancing crop production. To achieve this objective, the following key questions are addressed in this review:
i. To what extent have NPs and PGPM been studied together as a technique for promoting plant growth and enhancing crop yield?
ii. Which NPs and PGPM have been studied as plant growth and yield-enhancing agents?
iii. In what ways can NPs and PGPM be applied together to enhance plant growth and yield?
iv. What is the impact of NPs on the growth, viability, and functionality of PGPM?
v. What is the impact of NPs and PGPMs on plant growth and yield?
vi. What is the contribution of NPs and PGPM in ameliorating plant growth stress?
2 Materials and methods
Two databases, i.e., Scopus and Google Scholar, were used to search for relevant research articles to be included in this review. The search string used was: “PGPR” OR “PGPB” OR “rhizobacteria” OR “biofertilizer” AND “nanotechnology” OR “nano technology” OR “nanobiofertilizer” OR “nano biofertilizer” AND “plant growth.” The search process and results are shown in the PRISMA chart below (Figure 1). The following steps were followed during the selection process:
• The First step was article identification. The search string “PGPR” OR “PGPB” OR “rhizobacteria” OR “biofertilizer” AND “nanotechnology” OR “nano technology” OR “nanobiofertilizer” OR “nano biofertilizer” AND “plant growth” was used to identify articles to be included in the review. The aim was to look for articles that focused on three main issues, i.e., plant growth-promoting bacteria, nanotechnology, and plant growth. In Google Scholar, the advanced search was performed, where articles that were published between 2000–2023 were included. Sorting of the articles was done based on relevance, English pages only were included, and any type of document was specified in the document type check box, including patents and citations. A total of 8,936 articles were identified, of which 3,456 were from Scopus and 5,480 from Google Scholar.
• The second step was the pre-screening of the identified articles. The 8,936 articles that were identified were subjected to a pre-screening process. In Scopus, the pre-screening was done automatically, where searching was limited to include articles that were published between 2000 and 2023. Final published original journals, books, book series, or conference proceedings that are in English and open access only were included. In Google Scholar, pre-screening was done manually, where the open-access articles only were labeled as “Nano bio” and saved in my library. The pre-screening process led to the elimination of 7,769 ineligible articles and left 587 articles from Scopus and 580 articles from Google Scholar.
• After pre-screening, the screening process started, where the first screening was done manually in both databases. In this step, the documents in both databases were exported as a CSV file and saved. The screening was based on title relevance and removal of review articles. During this process, 918 articles were excluded, and the remaining 242 articles were subjected to further screening.
• The second screening process was then performed on 242 articles that passed the first screening. In this step, the screening was based on duplication, where a total of 59 duplicates were removed and leaving 183 articles.
• The Third screening process involved further removal of duplicates and irrelevant articles based on the abstract. In this step, the articles from both databases were combined, and articles that appeared in both databases were considered duplicates and removed. Then, abstracts were read, and irrelevant articles were removed. This step led to the elimination of 100 articles and left 83 articles.
• The 83 articles that passed the three screening stages were downloaded and saved. However, not all articles were retrieved; only 79 articles were successfully downloaded and saved.
• The saved articles were subjected to final screening based on full-text reading. Only 9 articles were irrelevant and were excluded. Therefore, the remaining 70 articles were considered for this review.
Figure 1. PRISMA flow chart showing the process of articles selection.
The inclusion and exclusion criteria used to determine the relevance of articles in each stage of screening are shown in Table 1.
Table 1. Inclusion and exclusion criteria used to select articles.
3 Results and discussion
3.1 Extent of research on the combined use of nanoparticles and plant growth-promoting microbes for plant growth promotion
This review focused on examining the interaction of two important emerging aspects of sustainable agriculture, i.e., nanoparticles (NPs) and plant growth-promoting microbes (PGPM). The 70 studies that are included in this review can be divided into six groups based on the objectives and nature of experiments that were carried out. The details on the designation of these studies are given in Figure 2. A total of 28 studies were conducted to test the effect of NPs and PGPR on the growth of plants as separate treatments and in their combination. Sixteen studies did the evaluation to determine the toxicological effects of NPs on PGPR. On the other hand, 10 studies did the encapsulation of PGPR on NPs and tested the effect of encapsulated PGPR on plant growth. Only 5 studies have evaluated the effect of commercially available nanobiofertilizer products. The remaining studies (11 studies) have conducted research on the toxicological effects of NPs on PGPR, and at the same time, evaluated the effect of NPs and PGPR on plant growth as either separate treatments or the encapsulated product.
Figure 2. Designation of articles that were included in the review.
Only six products were reported and tested (details of the products are shown in Table 2). Three products are nanobiofertilizers, and three are biofertilizers. These results imply that there is a huge demand for more research to develop products that will be available for farmers in the pace of promoting sustainable farming practices.
Table 2. Biofertilizers and nanobiofertilizer products that were tested and reported in the reviewed articles.
Furthermore, it is observed that there is an increasing number of research studies that are conducted on the subject matter year after year (Figure 3). Studies on PGPM as an alternative nutrient source for plant growth are not new, but the interaction between NPs and PGPR is a new trend in agricultural production. Based on the search criteria that were established during this review, in the years 2000–2007, there was no article that was retrieved. Only two articles were published in the years 2008–2011, and the number kept on increasing each year from 8, 16, to 44 in 2012–2015, 2016–2019, and 2020–2023, respectively.
Figure 3. Distribution of reviewed articles in chronological order.
3.2 Types of nanoparticles and plant growth-promoting microbes studied in the reviewed articles as plant growth and yield enhancers
3.2.1 Nanoparticles
According to Joudeh and Linke (2022), NPs are divided into three types based on composition, namely organic NPs, carbon-based NPs, and inorganic NPs. It was observed during this review that all three types of NPs can be successfully applied with PGPM to promote plant growth. Inorganic-based (ZnO and Silica) are the most studied NPs, followed by organic nanoparticles, mainly Chitosan and alginate. Carbon-based NPs are the least studied NPs, with only two studies reported in the selected articles. It was further observed that NPs can be used in a composite, i.e., more than one NPs can be applied together. A total of seven composite NPs were reported from different studies that were included in this review. The composite NPs studied were Chitosan polyvinyl alcohol, Laponite clay polyethylene oxide gel beads, Fe-coated nanofiber with activated carbon microbeads, Polymeric Fe, Chitosan coated mesoporous nano silica, polyvinylpyrrolidone-coated silver Engineered Nano Material, and Nano Fe Zn oxide.
3.2.2 Plant growth-promoting microbes
A total of 21 genera with more than 50 different species were observed to have a plant growth-promotion effect on different crops (Table 3). Two types of microbes were studied, these are, bacteria and fungi. In general, bacteria, specifically the free-living PGPR, are the most studied microbe (about 10 genera), followed by AMF.
Table 3. Plant growth-promoting microbes that were studied in the reviewed articles.
PGPR are the root rhizosphere bacteria that can enhance plant growth through different mechanisms such as hormone secretion, phosphate solubilization, and nitrogen fixation (Hasan et al., 2024). These bacteria have a lot of benefits, including: increasing nutrient availability, shoot and root development, protection against several biotic and abiotic stresses such as salinity, drought, and heavy metals (de Andrade et al., 2023). According to the results obtained from this review, the most studied genera of bacteria in promoting plant growth are Bacillus, followed by Pseudomonas, Azotobacter, and Azospirillum, which were reported in 35, 28, 12, and 8 articles, respectively. The results further stipulate that Pseudomonas has the highest number of investigated species (14), followed by Bacillus, Azospirillum, and Azotobacter, which have 13, 3, and 2 species, respectively. Rhizobium with one species, namely leguminosarum, is the only symbiotic PGPR genus that was reported in four research articles.
On the other hand, the most investigated group of Fungi is arbuscular mycorrhiza fungi (AMF). AMF protects host plants against various stresses such as extreme temperature, salinity, water shortage, and toxic heavy metals, thereby promoting plant growth and yield (Cui et al., 2018). Glomus is the most reported genus of AMF with five species (mosseae, fusculatum, clarum, intraradices, and etunicatum), which were reported in 6 articles. Another AMF that was reported is Piriformospora indica, which was reported in only one study.
3.3 Ways nanoparticles and plant growth-promoting microbes can be applied together
NPs can be applied with PGPM to promote plant growth in two ways, i.e., as separate treatments applied individually and in combination, or by formulating nanobiofertilizer through encapsulation, where NPs are used as carriers and protection for PGPM. Out of 70 studies that were included in this review, 36 studies have evaluated the effect of NPs with PGPM as separate treatments, and 13 studies have done encapsulation and evaluated the effect of encapsulated PGPM on plant growth. The commonly reported method of encapsulation is electrospinning, followed by emulsion methods, and mostly, the organic and composite NPs are used for encapsulation. All the reported processes of encapsulation in the reviewed articles were successful.
3.4 Impact of nanoparticles on the growth and viability of plant growth-promoting microbes
NPs can influence the growth and functionality of PGPM or can inhibit their growth and reduce their activities (Verma et al., 2024). A total 27 articles out of 70 articles that were included in this review have reported the impact of different NPs on different PGPMs. The effect of NP on PGPM, based on the articles included in this review, is summarized in Table 4. It is observed that different NPs affect PGPM in different ways, and the effect of nanoparticles on PGPM depends on the species of PGPM and the concentration of the NP. For instance, the studies on silver NP show that it suppresses the growth of most PGPM, but at higher concentrations, it increases production of IAA by B. mojavensis and reduces IAA production by S. meliloti, P. mosselii, and A. chroococcum. On the other hand, it is observed that TiO2 nanoparticles increase the ability of A. vinelandii and B. subtilis to produce ABA and Cytokinin and increase adhesion of P. polymyxa, A. faecalis, B. thuringiensis, and B. amyloliquefaciens onto the roots of plants. However, at higher concentrations, TiO2, CaO, ZnO, and Fe2O3 inhibit the growth of PGPM. While ZnO and CaO suppress the growth of PGPM. Gold NPs, Chitosan, SiO2 NPs, Al2O3 NPs, and nanogypsum were observed to increase the growth and viability of PGPM. Other NPs such as SiO2, CuO, and TiO2 accelerate the production of IAA, Exopolysaccharides, ABA, GA, Cytokinin, and P solubilization.
Table 4. Impact of nanoparticles on plant growth-promoting microbes.
These results show that there is a potential for using NPs in formulating biofertilizers to enhance the shelf life of bacterial cultures, plant growth, and productivity in agricultural fields (Perez et al., 2018). The concentrations of NPs should be observed during the formulation, as in most cases, higher concentrations of NPs reduce the viability of PGPM. Some NPs are toxic to PGPM; hence, precautions should be taken during disposal and application to prevent their effects on humans and the environment in general (Karunakaran et al., 2014).
3.5 Impact of nanoparticles applied with plant growth-promoting microbes on plant growth and yield
One of the promising applications of nanotechnology in agricultural production is in the improvement of biofertilizer formulation. The increased demand for safe and sustainable agricultural practices has pushed researchers to conduct research on the potential application of NPs along with biofertilizers in promoting plant growth. NPs can be applied with biofertilizers to promote plant growth in two ways, i.e., as separate treatments applied in combination or by formulating nanobiofertilizer through encapsulation, where NPs are used as carriers for PGPM.
Out of 70 investigated research articles, 54 articles have evaluated the effect of NPs with PGPM on the growth of different crops. A total of 13 studies did formulation of nanobiofertilizer by using NPs as carriers for PGPM, and 36 studies have tested the two (NPs and PGPMs) as separate treatments. The remaining 5 studies have evaluated the effect of commercially available nanobiofertilizers or biofertilizers with NPs on the performance of different crops.
A total of 25 crops were tested, as shown in Table 5. These crops are maize, rice, wheat, sugar beet, tomato, oilseed rape, common beans, triticale, pistachio, cabbage, peanuts, sunflower, eggplants, watermelon, ashwagandha, potato, soybean, rosemary, chili pepper, chick pea, radish, broccoli, grass pea, black eyed pea and fenugreek. Maize is the most investigated crop reported in 12 out of 53 research articles, followed by wheat and tomato, which are reported in 11 and 5 research articles, respectively. Sugar beet, black eyed pea, rice, and pistachio were reported in two articles only, while the remaining crops were reported only once.
Table 5. The impact of nanoparticles and plant growth-promoting microbes on crop growth and yield.
The findings of this review revealed that treatments involving combined applications of NPs and PGPM were superior in promoting plant growth as compared to when the treatments were applied singly.
3.6 Contribution of nanoparticles and plant growth-promoting microbes in ameliorating plant growth stresses
In the course of determining the influence of NPs and PGPM on promoting plant growth, some researchers have gone further in exploring the possibilities of using these technologies as a means to overcome biotic and abiotic stresses for plant growth. Both NPs and PGPM have a beneficial impact in protecting plants against pathogens and abiotic stresses such as salinity, water stress, and heavy metals (de Andrade et al., 2023; Kumari et al., 2024).
Out of 54 studies that evaluated the effect of NPs and PGPM on the growth of crops, 20 studies have also evaluated their influence on ameliorating plant growth stresses. The biotic stresses reported in the articles included in this review are mainly the soil-borne pathogens, which are reported in 9 research articles. A study conducted by Guardiola-Márquez et al. (2023) and Timmusk et al. (2018) demonstrated that application of Fe-coated nanofiber with activated carbon microbeads along with Paenibacillus polymyxa and TiO2 along with B. thuringiensis and P. polymyxa are effective in suppressing Fusarium oxysporum and Fusarium culmorum in chickpea and wheat, respectively. NPs and PGPM were also observed to be effective against Cochliobolus sativus, Candida glabrata, Sclerotium rolfsii and Alternaria brassicae in wheat, cabbage sprouts, rice, and oilseed rape, respectively. These results support the arguments made by Kumar et al. (2023) that the combined power of NPs and PGPR improves the plant’s ability to resist disease-causing organisms. Similar findings were also reported by Perveen and Mushtaq (2019).
On the other hand, the abiotic stresses that were reported in the reviewed articles are drought/water stresses, cadmium accumulation, salinity stresses, and wastewater. The influence of NPs and PGPM in reducing salinity stress was reported in 8 articles, while five articles have reported their influence in reducing drought/water stresses. In all articles, NPs and PGPM have shown positive results in reducing the adverse effects of salt and water stresses on plants and promoting plant growth.
4 Conclusion
A number of research studies have been conducted to explore the potential application of nanoparticles together with Plant growth-promoting microbes to promote plant growth and enhance crop yield. There is a potential for applying NPs with PGPMs to enhance plant growth and yield. The two technologies can be applied as either separate treatments applied in combination or by formulating nanobiofertilizer through encapsulation, where NPs are used as carriers and protection of PGPMs. Different NPs affect PGPMs in different ways, and the effect of NPs on PGPMs depends on the species of PGPM and the concentration of the NP. Higher concentrations of NPs affect PGPMs negatively; hence, precautions should be taken during the formulation. Combined application of NPs and PGPM helps to ameliorate plant growth stresses such as diseases, salinity, and drought, thereby promoting plant growth and yield.
Data availability statement
The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding author.
Author contributions
IM: Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Software, Supervision, Validation, Visualization, Writing – original draft, Writing – review & editing. EM: Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Software, Supervision, Validation, Visualization, Writing – original draft, Writing – review & editing. AM: Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Software, Supervision, Validation, Visualization, Writing – original draft, Writing – review & editing.
Funding
The author(s) declare that financial support was received for the research and/or publication of this article. This study was funded by the O. R. Tambo Africa Research Chair in Nanoscience, Nanotechnology, and Pheroids technology for enhanced antimalaria drug efficacy and optimized agricultural products in sub-Saharan Africa.
Acknowledgments
The authors would like to thank the O. R. Tambo African Chair initiative at NM-AIST for providing financial assistance.
Conflict of interest
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
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Keywords: nanobiofertilizer, nanoparticles, plant growth-promoting microbes, plant growth, nanotechnology
Citation: Massawe IH, Mbega E and Meya AI (2025) Potential application of nanotechnology in formulating biofertilizers as a sustainable way for promoting plant growth: a systematic review. Front. Sustain. 6:1584529. doi: 10.3389/frsus.2025.1584529
Edited by:
Mete Yılmaz, Bursa Technical University, TürkiyeReviewed by:
Marco E. Mng’ong’o, Mbeya University of Science and Technology, TanzaniaPradeep Kumar Rai, IFFCO-Nano Fertilizer Plant, Phulpur Unit, India
Ali Rıza Demirkiran, Bingol University, Türkiye
Münevver Müge Çağal, Bursa Technical University, Türkiye
Copyright © 2025 Massawe, Mbega and Meya. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Ikunda Herman Massawe, aWt1bmRhLm1hc3Nhd2VAbm0tYWlzdC5hYy50eg==
†These authors have contributed equally to this work