1 Introduction

The ever-increasing global population, coupled with rapid industrial and urban growth, presents a daunting challenge for sustainable agriculture [1]. The adoption of biological agents as substitutes for chemical fertilizers has led to a significant improvement in overall crop parameters. In the twenty-first century, climate change, food insecurity, and agricultural pollution present formidable challenges, negatively impacting plant growth, soil quality, and food security. Innovative techniques are essential to address these issues, as various stressors such as toxic heavy metals, organic pollutants, emerging contaminants, and other biotic and abiotic factors can disrupt nutrient availability, plant metabolic pathways, crop yields, and soil fertility. Among the promising strategies being explored to enhance plants’ tolerance to environmental stress, nanotechnology, particularly the application of nanoparticles, shows potential in improving plant functionality under adverse conditions. Nanotechnology is poised to revolutionize agriculture and pharmaceuticals, offering the promise of a more sustainable, efficient, and resilient agricultural and medical system. Nano-fertilizers, in particular, hold promise for enhancing nutrient utilization efficiency in plants through controlled and sustainable nutrient release [2,3,4]. Furthermore, farmers face multiple challenges, including rising input costs, such as fertilizers, fuel, and electricity, as well as dependency on bank loans, erratic monsoon patterns, and non-farm employment, hindering the realization of a 2nd green revolution [5]. Additionally, biotic and abiotic factors exert pressure on agricultural sustainability [5]. Chemical fertilizers adversely affect soil health, leading to reduced organic matter content, diminished water holding capacity, altered soil fertility, salinity, nutrient uptake, and disrupted soil structure and microbial diversity [6]. The persistence of these harmful chemicals poses a serious threat, leading to groundwater contamination [6]. To address the negative impacts of long-term chemical fertilizer use, organic farming has emerged as a dynamic alternative, responding to the rising demand for healthy food, sustainability in production, and growing pollution concerns [7]. While chemical fertilizers remain indispensable for global food demand, organic farming offers viable opportunities for specific plants and niche areas [8].

Biofertilizers, commonly known as microbial-based fertilizers, have emerged as vital components of sustainable agriculture, with their lasting effects on soil fertility [9]. These formulations comprise living microbial cells, either single or multi-species (mixed), which facilitate plant growth by enhancing nutrient availability through mineralization, solubilization, fixation, and acquisition [10, 11].The term “biofertilizer” encompasses various types, including nitrogen-fixing microorganisms, phosphorus and potassium solubilizers, mycorrhizae, and microbial consortia, and they are also referred to by other names such as microbial injections, soil injections, bioinoculants, microbial-based fertilizers, bioenhancers, phytostimulators, Plant Growth Promoting Rhizobacteria, or rhizoremediators. While biofertilizers show great promise, commercially available microbe-based biofertilizers have encountered challenges in field conditions, largely due to the survival of microbial inoculants under varying environmental conditions, limited farmer awareness, substandard formulation quality, and the lack of location-specific efficient strains [10]. In recent years, significant advancements, such as the use of specialized microorganisms, optimal technologies, and suitable carrier materials, have been made to enhance soil nutrient dynamics and promote plant growth. To ensure sustainable production and cost-effectiveness, the development of next-generation biofertilizers is imperative. These advancements include artificial selection of microbiomes, mixed inoculants, PGPR as biofertilizers, biofilm bio-fertilizers, nano bio-fertilizers, and bio-organo-chemical fertilizers [10]. Exploring these advanced biofertilizer technologies is essential to overcome existing limitations and foster a more sustainable and productive agricultural future.

2 Bacterial biofertilizers

They constitute a diverse group of bacteria, profoundly influencing plant growth through multiple mechanisms, such as nitrogen fixation, phosphate solubilization, siderophore production, disease protection, and rhizosphere engineering [12]. Some of these bacteria are proficient in nitrogen fixation and can establish either symbiotic associations with plants or exist as free-living non-symbiotic organisms. Notable examples of these growth-promoting bacteria encompass Rhizobium, Bradyrhizobium, Azotobacter, Azospirillum, Gluconoacetobacter, Frankia, Pseudomonas, Anabaena, Bacillus megaterium, Bacillus polymyxa, and Sinorhizobium [12].

3 Endophytes

Endophyte biofertilizers can be derived from both bacteria and fungi, each offering unique benefits to plant growth and health. Bacterial endophytes, such as those from the genera Azospirillum and Pseudomonas, enhance nutrient availability and produce growth-promoting hormones. Fungal endophytes, including species like Trichoderma and Piriformospora indica, improve nutrient uptake, disease resistance, and stress tolerance. By utilizing both bacterial and fungal endophytes, biofertilizers provide a comprehensive approach to enhancing agricultural productivity and sustainability.

Within the plant endosphere, a diverse array of microbial communities thrives, acknowledged for their pivotal role in maintaining plant health. The evolving field of plant–microbe interactions benefits from both modern genomic approaches and traditional Microbiology techniques, facilitating a deeper understanding of these intricate relationships. Endophytes, defined as symbiotic microbes that inhabit plants without causing harm, offer a promising avenue to bolster crop productivity while minimizing agricultural environmental footprints. These endophytes contribute to plant growth through mechanisms such as nitrogen fixation, phytohormone synthesis, and stress tolerance enhancement. Crucially, successful colonization by endophytes is imperative to confer these advantages to host plants. Despite the burgeoning interest in plant microbiome research, the precise mechanisms governing endophyte recruitment remain enigmatic. Bacterial endophytes, originating from the rhizosphere or phyllosphere, are fascinating organisms that play a crucial role in promoting plant growth and resilience. They contribute to soil fertility through processes like phosphate solubilization and nitrogen fixation. The potential applications of bacterial endophytes are vast, ranging from bioremediation to agriculture and biofuel production [13].

The symbiotic PGPB form mutualistic relationships with leguminous plants and are commonly affiliated with the Rhizobiaceae family. Conversely, non-symbiotic PGPR do not engage in such associations and instead encompass free-living or endophytic bacteria, like Azotobacter, Azospirillum, Cyanobacteria, among others [14]. This diverse array of PGPB collectively contributes to fostering sustainable plant growth and development, rendering them invaluable allies in the domains of agriculture and environmental sustainability (Table 1).

Table 1 Attributes and mechanisms of action in various plant growth promoting bacteria
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4 Rhizobacteria

Rhizobacteria are advantageous bacteria that inhabit the soil and engage with plant roots to augment growth. They utilise a range of strategies/processes including biological nitrogen fixation, phosphate solubilization, phytohormone production, siderophore production, induction of systemic resistance against phytopathogens, and production of enzymes such as ACC deaminase to reduce stress-induced ethylene levels. They are called as Plant Growth Promoting Rhizobacteria (PGPR). These actions not only enhance the well-being and productivity of plants, but also promote sustainable agriculture by decreasing dependence on chemical inputs (Table 1).

The rapid expansion of the human population, which puts pressure on crop productivity, closely links to the growth performance of plants in stressful environments, particularly in agriculture. Degraded land poses numerous stresses on plants, leading to decreased productivity and emerging as a major concern for addressing future food scarcity. Land degradation is a significant environmental issue at local, regional, and global scales, contributing to challenges such as drought, desertification, heavy metal contamination, and soil salinity, which hinder the achievement of several UN Sustainable Development Goals. Plants employ a variety of mechanisms to mitigate stresses associated with degraded land, with the rhizospheric system hosting various root-associated microbes that play a critical role in stress alleviation. Addressing the rising problem of iron-deficient soil due to increasing land degradation globally is essential for enhancing plant growth productivity. Thus, this review also aims to assess the stress status of plants caused by iron-deficient soil and explore potential eco-friendly solutions. Siderophores, known as iron-chelating agents produced by numerous microbes in the rhizosphere, represent sustainable and environmentally friendly agents that could potentially mitigate plant stresses on degraded land [39].

The presence of ample amounts of phosphorus, both in organic and inorganic forms, in the soil does not readily translate to its availability to plants, thereby posing a limiting factor for plant growth [40]. Phosphorus exists in insoluble forms in the soil, with plants absorbing it primarily as orthophosphate ions from the soil solution [41]. Soil microorganisms play a vital role in converting insoluble phosphorus into readily available forms through processes such as mineralization and solubilization [42]. Many bacteria, including those belonging to the Bacillus, Enterobacter, Pseudomonas, and Rhizobium genera, exhibit this ability [43].

Similarly, several microorganisms contribute to the enhanced availability of potassium through the process of solubilization, a crucial step enabling plants to utilize K effectively [44, 45]. K-solubilizing activity is predominantly observed in bacteria such as Acidithiobacillus, Bacillus, Burkholderia, Pseudomonas, Paenibacillus, and Rhizobium [46] thriving in the soil (Fig. 1).

Fig. 1
figure 1

Visual representation highlighting the symbiotic relationship between Plant Growth Promoting Bacteria (PGPB) and plants, showcasing their significance in agricultural productivity and sustainability

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Micronutrients such as iron (Fe), copper (Cu), boron (B), zinc (Zn), chlorine (Cl), manganese (Mn), nickel (Ni), silicon (Si), cobalt (Co), and molybdenum (Mo) play essential roles in plant growth and development [47]. Iron (Fe) availability can be enhanced through the action of siderophores, chelating compounds with low molecular weight that extract Fe3+ from the soil's mineral phase, converting it into soluble complexes readily accessible by plants [48]. Certain plants like wheat, rye, and barley exhibit higher resistance to iron deficiency due to the abundance of siderophores [49]. Iron is essential for microbial life but is often scarce in nature. Specific genes regulate the production of siderophores by microbes to efficiently acquire iron. Siderophores also influence microbial virulence and biofilm formation. They have potential applications for human, animal, and plant sustainability. Recent molecular advancements enhance our understanding of siderophore functions. Siderophores can also bind other metals, including Cu2+, Cd2+, Mn2+, Pb2+, Co2+, Al3+, Hg2+, and Ni2+, thereby enhancing their availability to plants [50]. Bacteria employ a variety of iron uptake systems to meet their iron requirements, indicative of the wide range of environments they inhabit. These systems for acquiring iron/heme can be categorized into two primary strategies. The initial strategy entails a direct interaction between the bacterial cell and external sources of iron/heme. Conversely, the alternative strategy depends on the production and secretion of specific compounds (known as siderophores and hemophores) by the bacteria. Once released into the surrounding environment, these compounds effectively gather iron or heme from a multitude of origins [51].

Zinc (Zn) deficiency poses a significant challenge to plants, leading to root necrosis, reduced biomass production, or even plant mortality [52]. Zn-solubilizing microorganisms act as biofertilizers, effectively addressing this deficiency by improving the availability of plant-accessible Zn in the soil [53]. These microorganisms employ various mechanisms for Zn solubilization, including acidification, chelation by ligands, and chemical transformations [45, 54]. Zinc solubilizing bacteria (ZSB) are integral components of the rhizosphere, possessing the capability to dissolve Zinc (Zn) from insoluble sources, thereby facilitating its uptake by plants. These bacteria employ a variety of molecular mechanisms, including the production of secondary metabolites such as organic acids, chelating agents, and phytohormones, to enhance Zn availability and support optimal plant growth. Crop-specific Zn-SB strains have been identified worldwide, particularly from genera like Bacillus and Pseudomonas, showcasing their potential in improving Zn Phyto availability and crop productivity. Researchers are actively exploring bacterial consortia tailored for diverse crops and environments. This review underscores the significance of Zn deficiency in soil, the edaphic factors influencing Zn accessibility, and the molecular regulation of plant Zn absorption and translocation, alongside elucidating the mechanisms underpinning Zn solubilization and the growth-promoting attributes of these rhizobacteria [55].

ZSB play a vital role in converting fixed soil zinc into readily available forms, thus enhancing plant zinc nutrition and fortification. One of the research group aimed to screen potent ZSB for plant growth-promoting (PGP) traits, characterize them biochemically and molecularly, and assess their impact on crop yield in field conditions. Two ZSB isolates, ZSB1 and ZSB17, efficiently solubilized insoluble zinc compounds and significantly improved maize crop growth. Biochemical analysis showed positive catalase and urease production, while both isolates exhibited various PGP attributes such as IAA production and phosphate solubilization. Molecular characterization revealed ZSB1 as Cupriavidus sp. and ZSB17 as Pantoea agglomerans, both exhibiting novel traits. These strains notably increased maize yield and zinc translocation to grains, showcasing their potential for biofortification and biofertilization technologies, thus contributing to soil health restoration [56].

In modern agriculture, rhizobacteria serve as beneficial biofertilizers to mitigate the adverse effects of Zinc (Zn) agrochemicals. However, their practical application is hindered by instability in field conditions. To address this, microbial formulations are being explored, aiming to provide a conducive microenvironment, protection, and effective rhizospheric colonization. This study focused on developing a new formulation for Zn-solubilizing bacteria E. ludwigii-PS10 using an extrusion technique, resulting in low-cost, eco-friendly, slow-release microbeads composed of alginate, starch, zinc oxide, and poultry waste. Characterization revealed spherical microbeads with high encapsulation efficiency and preservation of bacterial viability. Application of these microbeads to tomato plants notably enhanced biomass and Zn uptake, suggesting their potential in promoting plant growth and bacterial survival [57].

The significance of silicon (Si) deficiency in plants has gained recognition, leading to Si being listed as a beneficial nutrient by the Association of American Plant Food Control Officials (AAPFCO) in 2013 [58].

Several prominent genera, including Rhizobium, Bacillus, Burkholderia, Enterobacter, and Aeromonas, act as biofertilizers to enhance plant growth [59]. Among these, Rhizobacteria, a well-studied species, play a pivotal role in nitrogen fixation, potassium and phosphate solubilization, and production of phytohormones and siderophores, thereby promoting plant growth [60]. PGPB comprise bacterial species capable of symbiotic associations with plants, cyanobacteria, or bacterial endophytes [61]. These PGPB enhance plant growth through common mechanisms, including beneficial alterations in plant hormone release, resource mobilization, or reducing the impact of inhibitory molecules released by pathogens, protecting plants from biotic and abiotic stresses.

PGPB encourage the uptake of essential nutrients from the soil by utilizing various transporters and regulators, providing plants with micro and macro nutrients such as potassium, nitrogen, phosphorus, sulphur, and zinc [62]. Utilizing PGPB as biofertilizers holds promise for increasing crop production under diverse environmental conditions.

5 Algal biofertilizer

Algae encompass both eukaryotic organisms and prokaryotic cyanobacteria, constituting a photosynthetic group with remarkable morphological and biochemical diversity that significantly contributes to plant growth and development. In recent times, research on algal biofertilizers has witnessed increased attention, particularly focusing on cyanobacteria and microalgae as effective biofertilizers and soil conditioners. Microalgae are classified into various groups such as Chlorophyta (green algae), Rhodophyta (red algae), Phaeophyta (brown algae), Euglenophyta, Pyrrophyta, and Chrysophyta [63,64,65]. These green cell factories adeptly convert light, CO2, and nutrients into valuable molecules that enhance soil and plant health. Their exceptional efficiency in carbon dioxide capture leads to superior photosynthetic activity, resulting in higher metabolite and biomass production compared to terrestrial plants. Industries find algae appealing due to their ability to flourish with minimal freshwater supply and their potential to reclaim non-productive land.

Cyanobacteria, the simplest autotrophs, are widely distributed in the biosphere, using inorganic matter in water or soil to synthesize their food. Several unique features make cyanobacteria suitable as biofertilizers, including short doubling time, high water-holding capacity, atmospheric N2 fixation, and adaptability to extreme environmental conditions [66]. Consequently, cyanobacteria can modify the physico-chemical properties of soil, leading to higher crop yields, especially in rice. Their presence enhances soil porosity, promotes secretion of growth-promoting molecules like amino acids, vitamins, and hormones (gibberellin and auxin), improves water-holding capacity through their jelly-like structure, reduces soil salinity, suppresses weed proliferation, and, upon decomposition, enriches soil biomass content. The benefits of cyanobacterial inoculation have been observed in various other crops, including tomato, cotton, barley, maize, lettuce, radish, and sugarcane [67], Cyanobacteria enrich the soil with nitrogen, providing inexpensive nitrogen to plants while rendering the soil fertile and productive. The application of BGA biofertilizer, known as “algalization,” in rice cultivation fosters an environmentally friendly agro-ecosystem, ensuring economic viability while conserving energy-intensive inputs.

Nitrogen-fixing BGA includes filamentous species like Nostoc and Anabaena, along with non-filamentous species like Chroococcus. In filamentous BGA, nitrogen fixation occurs in specialized cells called heterocysts. Azolla-Anabaena, a notable example, is utilized as a biofertilizer in rice and various other crops. Azolla, also known as mosquito fern, duckweed fern, fairy moss, or water fern, forms a symbiotic relationship with a filamentous, nitrogen-fixing cyanobacterium called Anabaena. The fixed nitrogen is transferred to the host plant by the symbiont and incorporated into amino acids. These amino acids, along with reductants and photosynthate, are supplied to the symbiont [68] (Fig. 1).

6 Fungal biofertilizer

Fungi have emerged as valuable biofertilizers, playing a crucial role in promoting plant growth and improving soil health. Recent advancements in the application of promising fungal species on arable land have gained prominence, positively influencing soil quality [69, 70]. Fungal biofertilizers encompass various categories, including plant growth-stimulating fungi, compost formation fungi, phosphorus solubilizing and mobilizing fungi, and potassium solubilizing fungi.

Phosphorus solubilizing fungi aid in harnessing phosphate present in soil–plant systems and making it accessible to plants. Through solubilization and mineralization, these fungi unlock phosphate, improving the growth and yield of diverse crops. Utilizing phosphate-solubilizing fungi as an alternative to traditional phosphate fertilizers has shown promise in enhancing global agricultural productivity, soil fertility, reducing water pollution, and mitigating toxic waste accumulation [71]. This process involves the colonization of immediate plant root regions (rhizosphere) by microbial compositions, facilitating nutrient distribution to target crops and maintaining soil inhabitants despite adverse conditions [72]. Moreover, these fungi release nutrients continuously through their metabolism [73, 74]. There is increasing interest in exploring the role of fungal biofertilizers as biocontrol agents, as they promote crop growth and reduce dependence on synthetic chemicals.

Mycorrhizae are unique fungi forming mutual symbiotic relationships with plant roots, enhancing the uptake of phosphorus (P), nitrogen (N), zinc (Zn), copper (Cu), iron (Fe), sulphur (S), and boron (B). Various plants, including herbs, shrubs, trees, xerophytes, epiphytes, and hydrophytes, engage in mutualistic interactions with mycorrhizal species [75]. Arbuscular mycorrhizae (AM) and ectomycorrhizae (ECM) are among the most studied and significant mycorrhizal associations. There is a growing interest in using these fungal inoculants and genetically engineering dominant mycorrhizae to enhance yield and induce stress resistance. ECM fungi increase plant tolerance to abiotic stress, reduce soil toxins, and stabilize soil pH extremes while protecting plant roots from biological stressors [76]. AM fungi, as phosphate scavengers, expedite the recruitment of soluble phosphate from soil, making them highly efficient in nutrient uptake and soil-borne pathogen resistance. Their use as biofertilizers is gaining traction due to their proficiency in absorbing specific nutrients like P, Ca, Zn, S, N, B, and their positive impact on plant growth promotion, plant protection, and soil quality improvement as essential members of the soil microbial community [77, 78].

7 Nanobiofertilizers

For many years, the common agricultural practice involved the application of chemical fertilizers to boost productivity. However, the excessive use of these fertilizers has led to adverse effects on the ecosystem, including environmental toxicity, long-lasting residual actions, increased greenhouse gas emissions, groundwater and soil pollution, soil erosion, and impacts on animal and human health. Consequently, there is a growing need to explore nontoxic, eco-friendly alternatives like biofertilizers to achieve increased agricultural productivity without causing these associated side effects (Table 2).

Table 2 Impact of nanobiofertilizers on various crops
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Nanotechnology holds promise in revolutionizing sustainable crop production by addressing multifaceted stressors such as climate change and biotic/abiotic stresses. Tailored nanomaterials can modulate plant physiology, bolstering photosynthesis, redox balance, and nutrient uptake while activating stress defenses. Recent research delves into the uptake and mechanisms of nanomaterial action within plants, elucidating their interactions with hormones and stress responses. However, the dual nature of nanomaterials—acting as both stress alleviators and potential hazards—requires careful consideration, especially regarding dosage effects and toxicity. Understanding these dynamics is crucial for developing effective, eco-friendly nanomaterial-based solutions for resilient agriculture [79]

Global challenges like soil degradation and pollution threaten agricultural sustainability, despite past efforts to remedy them falling short due to cost or practical constraints. Nanotechnology now offers a promising solution, leveraging nanomaterials to enhance soil quality and crop yields sustainably. By manipulating soil microbes and improving nutrient availability, nanomaterials hold potential to rejuvenate soil health and foster robust crop growth. Evaluating the long-term impacts and practical applications of nanotechnology in soil management is crucial for realizing its full potential in sustainable agriculture [80].

Biofertilizers consist of live beneficial microorganisms such as Rhizobium, Azotobacter, Azospirillum, Blue-green algae (BGA), and fungal Mycorrhizae. These microorganisms positively influence plant growth and development by enhancing biological nitrogen fixation and solubilizing complex organic matter into simpler forms, making them readily available to plants. Biofertilizers also improve moisture retention, soil nutrient availability, soil microbial status, soil aeration, and natural fertilization [81]. However, biofertilizers face challenges like poor shelf-life, on-field stability, sensitivity to fluctuating environmental conditions, and the requirement of large doses for extensive coverage [82].

To address these challenges, researchers have turned to nanotechnology, which has emerged as the sixth most revolutionary technology after the green and biotechnology revolutions. Nano-biofertilizers, a hybrid combination of nano- and biofertilizers, offer enhanced nutrient use efficiency, reduced fertilizer consumption, sustained and slow-release agrochemicals, increased crop production, and minimal soil structure disturbance [83]. These nano-biofertilizers involve formulating organic fertilizers into nanosize (1–100 nm) with certain nanomaterial coatings, providing a more effective and eco-sustainable alternative for agriculture [84].

Researchers worldwide are investigating the potential role of nano and biofertilizers for agricultural aspects. Studies from Iran and India have reported significant improvements in crop growth, yield, nutrient absorption, and physiological parameters using nano-biofertilizers on various crops such as wheat, maize, sugar beet, black cumin, and grapevines [85,86,87,88,89,90,91,92,93]. However, there are concerns about the potential toxic effects of nanoparticles on human consumption, thus necessitating comprehensive experimental analysis and nano-toxicology assessment to ensure the safety and eco-friendly nature of nano-products [94] (Fig. 2).

Fig. 2
figure 2

Illustration highlighting the evolution and impactful role of Nanobiofertilizers in contemporary agriculture

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8 Mixed biofertilizer

Utilizing a mixture of microbial strains, as opposed to a single strain, is recognized as a significant approach in biofertilizer development, as it offers a broader range of mechanisms for enhanced plant benefits. Mixed inoculants consist of microbial consortia, facilitating a combined biofertilization effect that promotes nutrient uptake in plants. Recent studies have explored the combined impact of co-inoculants containing Arbuscular mycorrhizal fungi (AMF) and rhizobacteria to enhance the growth of leguminous plants [117]. Co-inoculants with multiple microbial species offer a wide range of biofertilizer efficacy and reliability, providing nitrogen fixation, phosphate solubilization, siderophore production, balanced growth, and nutrition compared to single inoculants.

A recent advancement in this field is the development of the culturomics technique, enabling the identification of bacterial species by cultivating them under multiple culture states. Various combinations of culturing conditions, growth media, incubation rates, and atmospheric conditions are employed to develop a diverse microbiome associated with plants and soil [10]. Another technique, the plant-dependent culturomics method, combines plant-associated media with culturomics to further enhance bacterial identification. Additionally, the KOMODO online database offers more than 18,000 strains mixtures and up to 3300 combinations of microbial variants, aiding in the development of effective media preparation in the laboratory to obtain suitable and desired species for biofertilizer inoculum [118].

9 Biofilm biofertilizer

Traditionally, farmers have used individual or mixtures of beneficial strains as biofertilizers to promote sustainable crop development. However, these biofertilizers face challenges when establishing and thriving in the rhizosphere or endosphere due to competition with soil and plant microflora [119]. To overcome these challenges, biofilm biofertilizers offer a potential solution. Microbial biofilms are communities of microorganisms that attach to surfaces, whether abiotic or biotic, and are enveloped in a matrix of self-produced extracellular polymeric substance (EPS) [120]. This matrix protects microbial cells from adverse environmental conditions.

Biofilm-forming microbes include bacteria, fungi, algae, and other microorganisms that work together through quorum sensing processes, functioning as a cohesive [121, 122]. Recent reports have highlighted the beneficial impact of biofilms on crop productivity. Compared to single microorganism-based biofertilizers, biofilm biofertilizers have shown significant advantages [123, 124]. Conventional biofertilizers face uncertainties in competing with native microflora, making them unpredictable [125]. Biofilm-forming bacteria as biofertilizers can overcome these challenges by providing a protective microenvironment that shields inoculants from adverse conditions and competition with native microflora [126]. The development of biofilm biofertilizers aims to enhance the resistance of indigenous microbial populations against pathogens and inhibitors [127].

Biofilm biofertilizers have demonstrated successful fertilizing capacity in various crops such as rice, maize, tea, rubber, and vegetables under field and greenhouse conditions. They have been able to reduce the usage of chemical fertilizers by up to 50% in many crops, something conventional biofertilizers have not achieved [128,129,130].

Biofilms can form on the plant surface or inside the plant, contributing to nitrogen fixation by PGPR and enhancing crop productivity. They also facilitate Zn solubilization and chelating agent production [79]. Compared to biofilms comprising a single microbial species, those with multiple strains have been found to be more resistant and sustainable. Biofilmed biofertilizers have emerged as a new inoculant strategy to improve biofertilizer efficiency and soil fertility [127]. These biofilms create a suitable environment for biofertilizers to compete and cope with soil's biotic and abiotic factors [131].

Moreover, multi-species biofilms have shown greater resilience compared to single-species biofilms [132]. Rhizobacterial biofilms often occur in mixed communities with interspecies interactions, making them more advantageous in nutrient and resource utilization [133]. Soil microbial biofilms can be categorized into bacterial biofilms, fungal biofilms, and fungal bacterial biofilms, with each type attaching to different surfaces in soil [134]. FBBs formed by non-filamentous fungi involve both bacteria and fungi acting as biotic surfaces [134]. These biofilms have been found to enhance nutrient uptake and environmental stress tolerance compared to non-biofilm-forming microorganisms [135]. Figure 3 depicts the different factors and stages involved in biofilm formation. Figure 4 illustrates the role of biofilm biofertilizers in promoting plant growth and development.

Fig. 3
figure 3

Overview of the factors and stages in biofilm formation

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Fig. 4
figure 4

Highlighting the contribution of biofilm biofertilizers in fostering plant growth and development

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Numerous studies have highlighted the potential of biofilm biofertilizers in enhancing ecosystem functioning and sustainability by improving soil fertility and protecting plants under adverse conditions [122]. These biofilm biofertilizers, also known as developed microbial biofilms, exhibit various beneficial functionalities such as hormone production, siderophore and hydrogen cyanide exudation, nitrogenase activity, antagonistic effects against pathogens, and solubilization and mineralization of organic and inorganic soil nutrients [136,137,138]. These biochemical activities contribute to enhanced plant growth [124] (Table 3).

Table 3 Effects of biofilm biofertilizers on different crops
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Biofilm biofertilizers have been found to increase P-solubilization, N2 fixation, siderophore production, and Zn solubilization [139,140,141,142]. Bacterial and fungal components of these biofilms play crucial roles in improving soil nutrient availability through processes like P-mineralization, solubilization, and biological nitrogen fixation, thereby enhancing soil fertility [138, 143, 144].

Studies have demonstrated the successful application of BFBFs in various crops in Sri Lanka, resulting in increased N-fixation, shoot and root growth, nodulation, and soil N-accumulation compared to conventional biofertilizers [143]. Mixed bacterial-fungal biofilms have been found in mycorrhizal roots, promoting P nutrition and improving plant development [145]. Fungal-rhizobial BFBF application significantly improved nitrogen use efficiency in Zea mays under drought conditions [146]. Additionally, BFBFs have been shown to produce phytohormones that positively influence plant physiology, leading to enhanced plant growth and defense stimulation against pathogens [31].

Furthermore, BFBFs have demonstrated their potential in increasing crop growth on saline soils and reducing the recommended dosage of chemical fertilizers by up to 50% [147]. Field trials using BFBFs with strawberry plants showed higher yields and improved fruit quality compared to conventional chemical fertilizers alone [148].

While BFBFs have shown promising results, further studies are needed to test their efficiency at a larger scale and optimize production processes for widespread use. Nevertheless, BFBFs have proven to be a viable and sustainable approach for enhancing plant nutrition and maximizing crop yields under different soil conditions in Sri Lanka [149].

10 Future prospects

Advancements in research and technology are expected to drive significant progress in the field of biofertilizers. Ongoing efforts are focused on enhancing production techniques, refining formulation methods, and optimizing application practices to maximize the efficacy and scalability of biofertilizers for farmers worldwide. The exploration of novel microbial strains and their symbiotic interactions with plants offers exciting opportunities for tailored biofertilizer solutions that can deliver precise nutrient supplementation, thereby boosting agricultural productivity and resilience. Cutting-edge Microbiological tools, including synthetic biology and genomics, are poised to revolutionize biofertilizer development. By leveraging these tools, researchers aim to engineer designer microbes with enhanced nutrient mobilization capabilities and stress tolerance, further enhancing the effectiveness of biofertilizers in diverse agricultural settings. Realizing the full potential of biofertilizers requires addressing several key challenges. These include selecting and optimizing biofertilizers for specific crops and agroecosystems, ensuring stringent quality control measures throughout the production and distribution processes, and conducting thorough ecological assessments to assess their long-term impacts on soil health and biodiversity. The future prospects of biofertilizers in agriculture hold immense promise and potential for transformative impact. These eco-friendly alternatives, harnessing the power of beneficial microbes, are poised to play a pivotal role in addressing pressing global challenges such as environmental sustainability, climate change mitigation, and reducing reliance on costly and harmful inputs. Establishing robust regulatory frameworks and standards, coupled with widespread adoption and acceptance among farmers and stakeholders, will be crucial for the successful integration of biofertilizers into mainstream agricultural practices. With continued innovation, collaboration, and investment, biofertilizers are poised to emerge as a cornerstone of sustainable agriculture, contributing to food security, environmental stewardship, and the resilience of farming communities worldwide.

11 SWOT analysis

Strengths

  • Active research and development efforts in the field of biofertilizers, leading to the development of advanced technologies

  • Government support Strong government initiatives and policies promoting the adoption of advanced biofertilizer technologies

  • Growing recognition of the importance of sustainable agriculture in India

  • India’s diverse agro-climatic conditions offer a wide range of bioresources for biofertilizer production

Weaknesses

  • Farmer skepticism

  • Infrastructure challenges

  • Limited adoption

  • Quality control

Opportunities

  • Opportunities for farmer training programs and awareness campaigns to promote the benefits of advanced biofertilizer technologies

  • Growing demand for Natural and sustainable agricultural products in domestic and international markets

  • Opportunities for continuous innovation and improvement in biofertilizer production techniques and formulations

  • Potential collaborations between government agencies, research institutions, and private sector companies to promote biofertilizer adoption

Threats

  • Competition

  • Economic viability

  • Environmental concerns

  • Regulatory challenges