Can Biologicals Replace Fertilizers? What Science Really Says

Dr. Ankita Garkoti
Jul 24
10 min read

Updated: 5 days ago

Introduction

Modern agriculture has relied heavily on synthetic fertilizers to meet the increasing global demand for food. The widespread use of nitrogen (N), phosphorus (P), and potassium (K) fertilizers has significantly increased crop productivity over the past century and played a major role in improving global food security. However, the long term dependence on mineral fertilizers has also created significant challenges, low nutrient-use efficiency, nutrient losses through leaching and volatilization, greenhouse gas emissions, soil degradation, and water pollution (1,2).

As agriculture moves toward more sustainable production systems, biologicals have emerged as one of the fastest growing innovations in crop nutrition. Biological products, including biofertilizers, plant growth-promoting rhizobacteria (PGPR), mycorrhizal fungi, and other beneficial microorganisms, improve nutrient availability, stimulate root development, enhance nutrient uptake, and strengthen plant tolerance to environmental stresses. Rather than supplying large quantities of nutrients themselves, these microorganisms improve the efficiency with which plants access nutrients already present in the soil or supplied through fertilizers (3,4).

This growing interest has sparked an important question among farmers, agronomists, and researchers: Can biologicals replace synthetic fertilizers?

Scientific evidence shows that biologicals have tremendous potential to improve nutrient-use efficiency and, in many cases, enable significant reductions in fertilizer inputs while maintaining crop productivity. These beneficial microorganisms stimulate root development, enhance nutrient cycling, improve soil biological activity, and help plants access and utilize nutrients more efficiently. As a result, numerous studies have demonstrated that biologicals can reduce fertilizer requirements while sustaining crop yield and quality under many production systems. Their greatest value lies in helping farmers produce more with fewer inputs while promoting long-term soil health, nutrient cycling, and agricultural sustainability. (3,5)

Rather than viewing biologicals and fertilizers as competing technologies, current research increasingly supports an integrated nutrient management approach, where biologicals complement mineral fertilizers to maximize crop productivity while reducing environmental impacts and improving soil sustainability. In this article, we examine what the scientific evidence really says about whether biologicals can replace fertilizers and where they fit within modern crop nutrition strategies.

What are biologicals

Biologicals are agricultural products derived from living organisms or natural biological processes that are used to improve plant growth, nutrient availability, stress tolerance, and soil health. Unlike synthetic fertilizers, which supply nutrients directly to crops in concentrated chemical forms, biologicals work primarily by enhancing the plant’s ability to acquire and use nutrients more efficiently.

Biologicals include several categories, such as biofertilizers, biostimulants, and beneficial microorganisms. Common examples include nitrogen fixing bacteria such as Azotobacter, phosphorus solubilizing bacteria such as Bacillus subtilis, beneficial fungi such as Trichoderma, and Arbuscular Mycorrhizal Fungi.

Biologicals are discussed in detail in our earlier blog on Understanding Biologicals for Sustainable Agriculture

Research shows that biologicals function through multiple mechanisms. Beneficial microbes can convert atmospheric nitrogen into forms plants can use, release organic acids that solubilize phosphorus locked in the soil, produce plant hormones that stimulate root growth, and improve soil microbial activity and organic matter cycling. These processes improve nutrient-use efficiency, allowing plants to obtain and use nutrients more efficiently, which supports healthy growth and development and ultimately leads to higher yields.

Image: Role of Biologicals in Sustainable Crop Production

Biologicals and Fertilizers: Understanding the difference

Although both biologicals and fertilizers are used to improve crop productivity, they serve different functions. Synthetic fertilizers supply essential nutrients such as nitrogen (N), phosphorus (P), and potassium (K) directly to plants, whereas biologicals improve the cycling, availability, and efficiency of nutrients already present in the soil or applied through fertilizer.

Beneficial microorganisms present in biological products can fix atmospheric nitrogen, solubilize phosphorus, mobilize micronutrients, stimulate root growth, and improve nutrient use efficiency through natural biological processes (3,6). As a result, biologicals are increasingly being used as complements to fertilizer programs rather than direct replacements. In many cropping systems, growers apply biologicals alongside reduced fertilizer rates to maintain productivity while lowering input costs and environmental impacts. (7)

This distinction is critical. Biologicals are not nutrient replacements; they are nutrient efficiency enhancers. Their value lies in helping crops make better use of nutrients already present in the soil. Research demonstrates that combining biologicals with reduced fertilizer rates can maintain or in some cases even improve crop yield and quality while reducing fertilizer inputs and minimizing environmental impacts (4). However, the ability of biologicals to reduce or replace fertilizer requirements depends on several factors, including crop species, soil fertility status, environmental conditions, management practices, and the specific biological product being used. Therefore, whether biologicals can completely replace fertilizers remains an active area of research, with ongoing studies evaluating their effectiveness across diverse agricultural systems.

Biofertilizers are an important category of biologicals. For a detailed comparison between biofertilizers and synthetic fertilizers, see our previous blog Biofertilizers vs. Synthetic Fertilizers: A Comprehensive Analysis of Benefits, Costs, and Application

How Biologicals Improve Plant Nutrition

Unlike conventional fertilizers, which directly supply mineral nutrients in plant-available forms, biologicals improve plant nutrition by stimulating the natural biological processes that regulate nutrient cycling, nutrient availability, and nutrient uptake within the soil–plant system. Beneficial microorganisms interact with plant roots and the surrounding soil microbiome to increase nutrient availability, stimulate root development, and improve nutrient-use efficiency. They accomplish this through several complementary mechanisms, including biological nitrogen fixation, phosphorus solubilization, micronutrient mobilization, the production of plant growth-promoting compounds, and the formation of symbiotic root associations. Rather than supplying nutrients themselves, biologicals help plants access and utilize nutrients already present in the soil or applied through fertilizer, resulting in healthier growth and improved crop performance. (3,5,6)

The effectiveness of biologicals depends on creating an environment where beneficial microorganisms can establish and remain active. These microbes perform best in soils with adequate organic matter, moisture, aeration, and favorable environmental conditions that support biological activity. In severely degraded or biologically inactive soils, improvements may occur more gradually as microbial populations establish, and soil health begins to recover. For this reason, biologicals are most effective when integrated with balanced fertilizer programs and sound agronomic practices that promote a healthy and active soil ecosystem.

Image: Potential interactions between crop roots and inoculants containing plant growth-promoting rhizobacteria (PGPR) and mycorrhizae for enhanced nutrient use efficiency

Source: Adapted from Adesemoye et al. 2017. Microbial Inoculants for Optimized Plant Nutrient Use in Integrated Pest and Input Management Systems. Probiotics and Plant Health.

Increasing Nitrogen Availability Through Biological Nitrogen Fixation

Nitrogen is an essential nutrient for plant growth, but atmospheric nitrogen (N₂) cannot be directly utilized by plants. Biological nitrogen fixation (BNF) is a natural process in which nitrogen-fixing microorganisms convert atmospheric nitrogen into ammonia (NH₃), making it available for plant uptake. Symbiotic bacteria such as Rhizobium and Bradyrhizobium fix nitrogen in legume root nodules, while free-living and associative bacteria such as Azotobacter and Azospirillum contribute to nitrogen availability in both legume and non-legume crops. Although biological nitrogen fixation does not completely replace synthetic nitrogen fertilizers in most cropping systems, it can significantly improve nitrogen availability, enhance nitrogen-use efficiency, and reduce fertilizer requirements under appropriate conditions (6,8).

Improving Phosphorus and Micronutrient Availability

Although many agricultural soils contain substantial amounts of phosphorus and micronutrients, many of these nutrients exist in insoluble or chemically bound forms that are unavailable to plants. Biologicals containing beneficial microorganisms improve nutrient availability by producing organic acids, phosphatases, siderophores, and other metabolites that solubilize phosphorus and mobilize essential micronutrients such as iron (Fe), zinc (Zn), and manganese (Mn). By increasing the pool of plant-available nutrients in the rhizosphere, these microorganisms enhance nutrient uptake, improve nutrient-use efficiency, and can reduce dependence on synthetic phosphorus fertilizers. (6,9)

Image: Microbial Mechanisms for Improving Phosphorus Availability

Source: Adapted from Sharma et al 2013. Phosphate solubilizing microbes: sustainable approach for managing phosphorus deficiency in agricultural soils. Springer Nature.

Building Larger and Healthier Root Systems

One of the most important ways biologicals improve plant nutrition is by promoting the development of larger and healthier root systems. Many plant growth-promoting microorganisms (PGPM), including species of Bacillus, Pseudomonas, Azospirillum, and arbuscular mycorrhizal fungi (AMF), produce phytohormones such as indole-3-acetic acid (IAA), cytokinins, and gibberellins that stimulate root elongation, lateral root formation, and root hair development. A more extensive root system increases the volume of soil explored, allowing plants to access greater amounts of water and nutrients, particularly relatively immobile nutrients such as phosphorus. As a result, biologicals enhance nutrient uptake, improve nutrient-use efficiency, and increase plant resilience under environmental stress. (3,6)

Improving Nutrient Absorption through Mycorrhizal Associations

Arbuscular mycorrhizal fungi (AMF) form beneficial symbiotic associations with the roots of nearly 80% of terrestrial plant species. Their extensive network of fungal hyphae extends far beyond the root zone, increasing the volume of soil explored for nutrients and water. This expanded absorptive surface enhances the uptake of relatively immobile nutrients, particularly phosphorus, as well as zinc (Zn), copper (Cu), and other micronutrients. In return, the plant supplies the fungi with carbohydrates produced through photosynthesis. Beyond improving nutrient acquisition, mycorrhizal associations also enhance nutrient-use efficiency, increase drought tolerance, and contribute to overall plant growth and soil health (10,11)

Can Biologicals Reduce Fertilizer Requirements? What the Research Shows

One of the most common questions surrounding biologicals is whether they can reduce the need for synthetic fertilizers. Current research suggests that the answer is yes, but only under the right conditions and not as a complete replacement. Numerous field studies have shown that, under appropriate soil, crop, and management conditions, biologicals can help maintain comparable crop yields even when fertilizer rates are reduced by 25–50%, and in some cases even more. However, results vary depending on factors such as crop species, soil fertility, climate, microbial strain, and overall management practices. These benefits are largely attributed to improved nutrient availability, enhanced root growth, increased nutrient-use efficiency, and greater soil biological activity rather than the direct supply of nutrients by the biological products themselves. (3,4,6)

While individual field trials often report variable results due to differences in climate, soil type, crop species, microbial strains, and management practices, meta-analyses provide a more reliable assessment by combining data from hundreds of independent experiments. One of the largest global meta-analyses, conducted by Schütz et al. (2018), analyzed 171 peer-reviewed studies on microbial biofertilizers across diverse crops and production environments. The analysis found that microbial biofertilizers consistently increased crop yields while improving nitrogen- and phosphorus-use efficiency, with average yield gains of approximately 8–20%. The greatest benefits were observed under water-limited conditions and in soils with moderate nutrient deficiencies. Similarly, numerous studies have reported enhanced nutrient uptake, greater root biomass, and increased soil microbial activity following inoculation with plant growth-promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF). (5)

Importantly, these studies reached a common conclusion: the most consistent and significant yield improvements occurred when biologicals were used in combination with balanced fertilizer programs rather than as complete fertilizer replacements.

However, research also demonstrates that biologicals alone cannot consistently meet the nutrient demands of high-yielding cropping systems, especially where soils are nutrient deficient. Their performance depends on several factors, including crop species, soil fertility, climate, microbial strain, and management practices. Consequently, the greatest and most consistent agronomic benefits are achieved when biologicals are used alongside balanced fertilizer programs as part of an Integrated Nutrient Management (INM) strategy. This integrated approach improves fertilizer-use efficiency, reduces nutrient losses, supports soil health, and enables farmers to achieve high productivity while lowering environmental impacts. (3,4,6)

Why Biologicals Are Becoming Essential in Modern Agriculture

The increasing adoption of biologicals reflects a shift toward more efficient and sustainable crop production. Rising fertilizer costs, declining soil health, climate-related stresses, and growing environmental concerns have highlighted the need for complementary technologies that improve the efficiency of existing agricultural inputs. Rather than replacing fertilizers, biologicals enhance their effectiveness by increasing nutrient availability, improving nutrient-use efficiency, stimulating root growth, and supporting beneficial soil microbial communities. (3,6)

For many growers, the value of biologicals extends beyond reducing fertilizer inputs. By improving nutrient-use efficiency, promoting stronger root systems, and enhancing crop resilience to environmental stresses such as drought and heat, biologicals can contribute to more consistent crop performance and improved return on investment. Even when fertilizer rates remain unchanged, increasing the efficiency with which plants access and utilize nutrients can help maximize the value of every nutrient applied while supporting long-term productivity and profitability.

In addition to improving crop nutrition, biologicals contribute to healthier and more resilient soils by promoting nutrient cycling, increasing soil biological activity, and reducing nutrient losses through leaching and volatilization. Many biological products also help crops better tolerate abiotic stresses such as drought, heat, and salinity, resulting in more stable growth under challenging environmental conditions. These benefits align closely with the goals of regenerative and climate-smart agriculture, where maintaining soil health and maximizing resource-use efficiency are key priorities. (3,6)

As scientific understanding and field validation continue to expand, biologicals are increasingly recognized as an essential component of integrated crop nutrition. When used alongside balanced fertilizer programs and sound agronomic practices, they help farmers produce higher-quality crops with fewer inputs while improving the long-term sustainability and resilience of agricultural systems.

Conclusion:

Current scientific evidence shows that biologicals are not a complete replacement for synthetic fertilizers, but they are an increasingly important tool for improving crop nutrition. Rather than supplying large amounts of nutrients directly, biologicals enhance nutrient availability, stimulate root development, improve nutrient-use efficiency, and support a healthy and diverse soil microbiome. These natural biological processes enable crops to make better use of nutrients already present in the soil or supplied through fertilizer, helping growers improve productivity while supporting long-term soil health.

Research consistently demonstrates that the greatest agronomic, economic, and environmental benefits are achieved when biologicals are integrated with balanced fertilizer programs as part of an Integrated Nutrient Management (INM) strategy. By improving nutrient-use efficiency, reducing nutrient losses, and increasing crop resilience, biologicals help farmers produce more with fewer inputs while building healthier, more sustainable production systems for the future.

At Nurture Growth, we believe the future of crop nutrition is built on the synergy between biology and conventional fertility programs, not choosing one over the other. Our proprietary consortium of beneficial microorganisms is designed to complement existing fertilizer programs by supporting nutrient cycling, enhancing root development, improving nutrient availability, and promoting long-term soil health. As scientific research continues to advance, integrated biological solutions will play an increasingly important role in helping growers maximize productivity, improve profitability, and farm more sustainably for future generations.

While scientific research supports using biologicals as part of an Integrated Nutrient Management (INM) strategy, growers are adopting biologicals in different ways based on their production systems, soils, crops, and management goals. Many incorporate biologicals alongside conventional fertilizer programs to improve nutrient-use efficiency and support soil health, while others have successfully reduced, or in some cases replaced synthetic fertilizer applications based on their own on-farm experience and results. Because every farming operation is unique, growers should evaluate biologicals under their own field conditions and work with a qualified agronomist to determine the approach that best meets their agronomic and economic objectives.

Blogger Biography:

Dr. Ankita Garkoti is a Senior Science Officer at Nurture Growth Bio Fertilizer. She has over 9 years of experience in Agriculture research and extension. Her areas of specialization encompass Plant Pathology, Microbiology, Plant Protection, Organic farming, Biofertilizers, Organic Fertilizers, and Biocontrol agents.

She holds a Ph.D. in Plant Pathology and a master's degree in Botany with a specialization in Plant Pathology. Her doctoral research involved an in-depth study of lentil wilt and its management through various practices. She has extensive experience in organizing training programs on Organic and Natural farming techniques for farmers, agricultural growers, students and other stakeholders.