Modern agriculture hinges on a single strategy: achieving higher yields with less nitrogen fertilizer , without harming the soil or the farmer's finances. In this context, biofertilizers have become a key tool for using nitrogen and other nutrients more efficiently, while simultaneously protecting the soil ecosystem.
Far from being a passing fad, biofertilizers and biostimulants represent a shift in approach: moving from purely chemical, high-dose fertilization to smarter nutrition, supported by beneficial microorganisms, well-managed organic matter, and tools that improve the soil's capacity to retain and recycle nutrients. We'll examine, in detail and frankly, how they work, the different types available, how to choose them, and how to integrate them into a truly efficient nitrogen fertilization plan.
What are biofertilizers and why are they key for nitrogen?
When we talk about biofertilizers, we are referring to products of organic and/or microbial origin that improve soil fertility and crop nutrition, either by providing nutrients, making them more available, or activating biological processes that promote their absorption. They can be based on plant remains, manure, compost, microorganisms such as bacteria and fungi, or combinations of all of these.
What distinguishes them from conventional mineral fertilizers is that they work alongside soil biology rather than replacing it. They not only provide nutrients but also promote microbial activity, humus formation, and rhizosphere balance, creating a more stable and resilient "nutrient storehouse" in the face of water, heat, or salinity stress.
Furthermore, many microbial biofertilizers are formulated with PGPR bacteria (plant growth-promoting rhizobacteria) or specific fungi that directly participate in processes such as the biological fixation of atmospheric nitrogen , the solubilization of phosphorus and calcium, and the improvement of micronutrient absorption. These mechanisms allow for a realistic reduction in mineral nitrogen application rates without compromising production, and can even increase it in well-managed soils.
It is important to distinguish them from biostimulants : biofertilizers provide or mobilize nutrients and improve fertility, while biostimulants focus on activating physiological processes of the plant (better rooting, stress tolerance, etc.) without being, strictly speaking, a primary source of nutrients.
Functions of biofertilizers in modern agriculture
Biofertilizers perform many functions at once, and this is what makes them especially interesting when seeking to optimize the use of nitrogen and other key elements in cultivation.
Provision of essential nutrients such as nitrogen, phosphorus, potassium and different micronutrients: depending on the type of biofertilizer, they can provide these elements directly (for example, through decomposed organic matter) or facilitate their transition from forms that are not readily available in the soil to forms that can be assimilated by the plant.
They also contribute to improving the soil's physical structure . By increasing organic matter and promoting the formation of stable aggregates, they enhance water retention capacity, aeration, and cation exchange capacity. This results in better root development and more efficient nitrogen use, as less nitrogen is exposed to leaching and runoff losses.
Another key function is the stimulation of beneficial microbial activity . Many products contain nitrogen-fixing bacteria, mycorrhizal fungi, and other PGPR that colonize the rhizosphere and help break down organic matter, release nutrients, and compete with soil pathogens. All of this promotes a more stable and productive root environment.
The overall effect is a reduction in dependence on synthetic chemical fertilizers . This isn't about eliminating them entirely, but rather adjusting the doses to what the crop actually needs, relying on soil biology to cover a significant portion of its requirements. This reduces nitrate pollution, greenhouse gas emissions, and the risk of nutritional imbalances.
Ultimately, soil enriched with biofertilizers and managed consistently tends to produce higher quality crops : greater nutritional and organoleptic content, more uniform fruit, better sizes, and plants less prone to stress. All of this translates into higher commercial value and greater production stability season after season.
Types of biofertilizers and how they affect nitrogen use
Within the umbrella of biofertilizers, we can find very different products, each with a specific role in nutrition and nitrogen management. Ideally, in agronomic practice, several tools are combined to meet the diverse needs of the soil-plant system.
Another star product is worm castings , the result of earthworm digestion of organic matter. This highly stabilized biofertilizer is rich in humic and fulvic acids and has a remarkable ability to chelate nutrients. It releases nitrogen and other elements gradually, improves root development, increases root biomass, and stimulates microbial activity. It is especially valued in organic farming for its ability to strengthen soil fertility in the medium and long term.
Fast-absorbing liquid fertilizers formulated from organic matter and specific extracts allow for a rapid response to the crop's specific needs, especially in intensive farming systems. They are typically applied via fertigation or foliar spray, and help correct deficiencies or meet periods of high demand for nitrogen, phosphorus, or potassium with high efficiency, provided they are applied at the correct dosage.
We also find slow-release composted fertilizers, very rich in carbon, which gradually mineralize. Their continuous use helps to form stable humus , retain nutrients in the clay-humus complex, and reduce nitrogen losses through leaching. They are perfect allies for fertilization plans that aim for stability and reduced mineral doses.
Finally, the incorporation of beneficial microorganisms such as nitrogen-fixing bacteria, phosphorus-solubilizing bacteria, mycorrhizal fungi, and specific PGPR multiplies the impact of other organic fertilizers. These microorganisms improve nutrient absorption, help control pests and diseases through competition and antibiosis, and maintain a biological balance in the soil, resulting in more efficient nitrogen use and stronger plants.
Microbial biofertilization and PGPR: nitrogen fixation and efficiency
Biofertilization using PGPR bacteria is a game-changer because it directly influences nitrogen dynamics in the soil-plant system. These rhizobacteria, whose natural habitat is the rhizosphere, exert both direct and indirect effects on crop growth.
Among its direct effects are the fixation of atmospheric nitrogen into forms that plants can assimilate, the solubilization of scarce mineral elements such as phosphorus, iron, and calcium, and the production of phytohormones (auxins, gibberellins, cytokinins, ethylene) that stimulate rooting and vegetative development. A plant with a more robust root system explores the soil more effectively and makes better use of the nitrogen present.
Regarding indirect effects, many PGPRs produce siderophores that capture iron and make it more accessible, as well as lytic enzymes (chitinases, glucanases) and antibiotics that participate in biocontrol mechanisms against soil pathogens. Some even generate hydrogen cyanide in doses that allow them to compete with harmful microorganisms, fitting within the plant's natural defenses.
Among the most widely used genera in agriculture are Rhizobium, Burkholderia, Pseudomonas, Bacillus, and Azospirillum. Pseudomonas putida , for example, is particularly interesting for its ability to solubilize phosphorus, calcium, and iron, synthesize phytohormones, increase soil enzyme activity, and trigger a systemic priming response in the plant, better preparing it to withstand stress.
A commercial biofertilizer based on *P. putida*, formulated with a highly resistant strain and prebiotics to promote its establishment, can increase the efficiency of fertilization programs to the point of reducing the use of conventional fertilizers by at least 35%, thanks to its high nutrient solubilization capacity and the increased efficiency of nitrogen and potassium uptake. Furthermore, it helps generate more root biomass, accelerates the humification and mineralization of organic matter, competes for space with other pathogens, and can participate in the bioremediation of contaminated soils.
These microbial products are often complemented with soil prebiotics that improve the physical, chemical, and biological structure of the soil profile (for example, formulations rich in humic substances or organic nitrogen sources such as N-VIGOR). This creates an ideal environment for the bacteria to establish themselves, multiply, and reach their full potential, benefiting the crop.
Microbial biofertilizers in practice: protocols and results
In the field, the coordinated use of liquid humus and bacterial consortia offers highly consistent results. Microbiological nutrition protocols applied in intensive crops have shown clear improvements in vegetative development, uniformity, and yield when several applications are made throughout the cycle.
In a broccoli trial in the Region of Murcia, on a farm belonging to a company committed to sustainability and reducing chemical fertilization, a program based on liquid humus and nutrient-solubilizing and fixing bacteria was used. After three monthly applications via fertigation, greater vegetative development , more uniform greenness, more homogeneous plants, and an increase in marketable production were observed.
In another practical case, in a conventional zucchini crop in an area of ​​intensive agriculture, a farm using a microbiological nutrition protocol (liquid humus and a Bio NPK-type microbial biofertilizer) was compared to a control farm using traditional mineral fertilizer. Despite reducing synthetic fertilizer by around 35%, the farm managed with microbial biofertilizers achieved higher yields and more vigorous and uniform plants, demonstrating that it is possible to reduce mineral nitrogen without losing production when the soil microbiology is activated.
Testimonials from farmers who use liquid humus on woody crops, such as pistachios, highlight benefits such as the creation of a protective ecosystem around the roots , increased nutrient absorption, greater quantity and quality of fruit, improved water retention, and greater resistance to soil pathogens. Application can be done via irrigation or as a foliar spray, adapting to the specific characteristics of each farm.
Behind these results there is usually a holistic approach, sometimes structured around comprehensive microbial management models. These types of strategies rely on certified organic biofertilizers, capable of establishing symbiosis with the roots , colonizing the rhizosphere and rhizoplane, and supplying plants with nitrogen, phosphorus, potassium, water, iron, and micronutrients precisely when they need them, preventing excesses and deficiencies.
How to choose the right biofertilizer for your crop
With so many options available, it's common for farmers to feel a bit lost when choosing a product. The key is to start from the premise that there's no single perfect biofertilizer for everything , but rather the right combination for your soil, your crop, and your irrigation system.
The first step should be to conduct a comprehensive soil analysis , including texture, organic matter, pH, nutrient levels (including available phosphorus and potassium), and, whenever possible, a basic assessment of biological activity. This allows for the detection of deficiencies, nutrient lockouts, salinity, or structural problems that will determine the most suitable type of biofertilizer.
The type of crop and its phenological stage must also be carefully considered . Some products work particularly well in intensive horticulture, others in woody crops such as olives, vines, or pistachios, and still others are designed for extensive crops like cereals. The crop stage (establishment, vegetative development, flowering, fruit set) will determine which formulations should be prioritized and how to adjust the doses of mineral nitrogen.
Soil conditions (texture, structure, drainage, lime content, salinity) largely determine the response to biofertilizers. In compacted or highly degraded soils, it is advisable to prioritize products that improve structure and increase organic matter , while in light soils with low water retention capacity, the combination of compost, vermicompost, and microbial consortia can make a significant difference in nitrogen efficiency.
It's always a good idea to have the support of technicians specializing in biofertilization, who can interpret the analyses and design a tailored protocol. Their field experience can save many failed trials and help integrate biofertilizers into the existing fertilization plan , avoiding overlaps and taking advantage of synergies with irrigation, crop rotation, and other management practices.
Calculation of nutritional needs and nitrogen adjustment
For biofertilizers to truly improve nitrogen efficiency, it's essential to accurately calculate the crop's nutritional needs and adjust fertilizer doses thoughtfully, not arbitrarily. Otherwise, even with biofertilization, we can still lose nitrogen due to over-application.
The starting point is defining the target yield, that is, the maximum harvest that could be achieved if everything works correctly. Based on this target, nutrient uptake tables for each crop are consulted to estimate the units of nitrogen (N), available phosphorus (P2O5), and soluble potassium (K2O) that the crop will need during its cycle. These needs are usually expressed as three numbers, for example, 100-120-60.
Once the total needs are known, it is necessary to assess what the soil already provides: nitrogen released by the decomposition of the previous crop residue, residual phosphorus and potassium, and nutrients from previous applications of slow-decomposing organic matter . Unlike nitrogen, which is highly mobile and can be easily lost, phosphorus and potassium tend to remain in the soil, so its fertilization history is relevant.
Subtracting the nutrients that the soil can naturally provide from the total needs of the crop, we obtain the amount of nutrients that must be supplied with fertilizers . From there, this amount is translated into kilograms per hectare of the different products (minerals and biofertilizers) based on their nutrient content and release method.
The use of biofertilizers that fix nitrogen or improve its efficiency allows for a reduction in the units of mineral N needed, but this reduction must be justified by trial data, previous experience and field monitoring (soil and plant analysis) to avoid falling short or exceeding the required amount.
Dosage and application methods of biofertilizers
Dosage is one of the areas where mistakes are most common. The idea that "more is better" doesn't hold true: an incorrectly dosed biofertilizer can be inefficient or even counterproductive . Each product comes with specific dosage recommendations per hectare or per cubic meter of irrigation water, and these should be followed, with slight adjustments depending on the specific circumstances.
Solid biofertilizers (compost, solid humus, composted pellets) are usually applied to the soil before sowing or planting , lightly incorporating them into the surface layer. In woody crops, they can also be applied as a top dressing along the drip line, allowing rain or irrigation to facilitate their gradual absorption.
Liquid biofertilizers, both organic and microbial, are frequently applied through the irrigation system, allowing for homogeneous distribution in the rhizosphere. For formulations containing live microorganisms, it is essential to adhere to recommendations regarding compatibility (avoiding mixtures with certain products with extreme pH levels or with biocides that could harm them) and application timing.
Many microbial formulations are also used as foliar solutions, aiming to colonize the plant surface and take advantage of entry points through stomata and cuticle. In these cases, it is important to apply them during periods of low sunlight and good relative humidity so that the microorganisms can establish themselves properly.
In all cases, over-application and unnecessary treatments should be avoided. Using soil, irrigation water, and, when possible, foliar analyses helps to adjust the dosage and frequency so that each application is meaningful and integrated into the overall fertilization plan.
Biofertilizers, biostimulants and fertilizers: key differences
In the field it is not uncommon for terms to be confused, so it is important to clarify the differences between biofertilizers, biostimulants, fertilizers and plant protection products, especially from the point of view of regulations and agronomic management.
Fertilizers, in general, are products that provide nutrients (N, P, K, and others) so that plants can grow. They can be mineral (synthetic) or organic. Traditional mineral fertilizers usually have high concentrations of nutrients, but when applied in excess or without proper guidance, they can contaminate soil and water and cause nutritional imbalances.
Biofertilizers are classified as organic or microorganism-based fertilizers. They are characterized by being 100% natural or biological in origin and by not generating environmental impacts similar to chemical fertilizers when used correctly. Their main function is to provide nutrients and, above all, improve their availability and utilization by plants, regardless of the direct nutritional content of the inoculant.
Biostimulants, on the other hand, are not considered fertilizers in the strict sense. They are defined as substances or materials (excluding nutrients and pesticides) that, when applied to plants, seeds, or growing media, modify physiological and biochemical processes , improving growth, development, or tolerance to abiotic stress. They are not intended to directly control pests or diseases, nor to be the primary source of nutrients.
Plant protection products are mixtures of active substances designed to protect plants against harmful organisms (weeds, fungi, insects, etc.). They operate through mechanisms entirely different from fertilizers and biostimulants, and are regulated by other specific regulations. Therefore, a product that acts directly against pests or diseases falls under the category of plant protection products, not biostimulants.
In practice, the most efficient approach is usually to combine fertilizers (mineral and organic), biofertilizers, and biostimulants, taking advantage of the fact that each group contributes a different piece of the puzzle: nutrition, fertility improvement, and physiological activation , all aligned to make better use of nitrogen and reduce dependence on chemical inputs.
Advantages and disadvantages of biofertilizers and biostimulants
Although the benefits are many, it is important to have a realistic view of what biofertilizers and biostimulants can and cannot do, as well as their potential drawbacks when they are chosen or handled incorrectly.
Among the potential drawbacks is the risk that a poorly manufactured or improperly handled biofertilizer may contain pathogens, especially if it has not undergone proper sanitization processes. It is also true that some organic products can be more expensive than conventional mineral fertilizers, particularly if they are highly technical formulations or contain selected microorganisms.
Another point to consider is that certain biofertilizers may have more limited or unbalanced nutrient content relative to the crop's needs, so simply applying them is not enough: they must be integrated into a comprehensive plan that addresses any deficiencies. Furthermore, the preparation, handling, and application of some products may require more labor and time, something that must be taken into account on farms with limited staff.
On the positive side, the advantages are compelling: they improve crop productivity, the quality of the final products, help optimize and reduce the use of mineral fertilizers , contribute to a more efficient use of water, minimize the pollution of water bodies, require less energy for their production than synthetic nitrogen fertilizers, and promote long-term soil conservation.
Furthermore, its use is closely aligned with organic farming and the growing demands of consumers, who are calling for food produced with a lower environmental impact. The result is healthier and more resilient crops , with a clear added value in markets that value sustainability.
Economic and regulatory context: nitrogen fertilizers in crisis
Recent events have highlighted the limitations of the model based on large doses of synthetic nitrogen fertilizers. Geopolitical tensions, such as the war in Ukraine, have brought to the forefront the dependence of many countries on nitrogen imports , in which Russia has been a key player, and the significant impact of natural gas prices on fertilizer production costs.
In just two years, the price of many fertilizers has tripled, creating a real problem for the profitability of farms. This situation has forced a rethinking of strategies and has boosted interest in alternatives that reduce dependence on conventional fertilizers , where biofertilizers and biostimulants have gained clear prominence.
At the same time, European policies, in line with the Green Deal and the Farm to Fork strategy, set targets such as reducing the use of agrochemicals by 50% and the use of fertilizers by 20% by 2030. The regulations have been updated to include biofertilizers and biostimulants within regulated fertilizer categories, facilitating their registration and marketing under a clearer legal framework.
In Spain, for example, a specific group of microorganism-based products with biostimulant characteristics and properties is included, allowing innovative companies to introduce microbial solutions to improve nutrition and nitrogen efficiency with greater legal certainty. Even so, the market for these products still has room to grow compared to regions like South America, where their use is more widespread.
Market studies point to remarkable growth in the biostimulants and biofertilizers sector in Europe in the coming years, with rates close to 9-10% annually, driven by the need for more sustainable agriculture, the increase in the consumption of organic food and technological advances in the formulation of microbial and organic products.
Types of biofertilizers according to their function and origin
If we refine the classification a little more, we can group biofertilizers according to their main function in the soil and in the plant , which helps a lot when selecting the most suitable product for each situation.
Among nitrogen-fixing biofertilizers are those formed by bacteria that capture atmospheric nitrogen and transform it into forms that the plant can use. There are symbiotic fixers, such as Rhizobium in legumes, and free-living fixers, such as Azotobacter or Azospirillum , which act in the rhizosphere of many crops.
Phosphorus-solubilizing biofertilizers contain microorganisms capable of lowering the pH in the root zone and releasing phosphorus that was in insoluble forms, locked in the soil. This is key to improving the efficiency of applied phosphorus and reducing the necessary doses.
Mycorrhizal phosphorus fixers form close associations with plant roots, extending their effective surface area and improving the uptake of water and nutrients, especially phosphorus, in soils with low availability. In exchange for carbon from the plant, the fungus provides privileged access to nutrient sources that are otherwise difficult to access.
Another important group is plant growth-promoting biofertilizers, formulated with microorganisms capable of producing and releasing substances that play a role in plant growth and physiology, such as hormones and organic compounds. Although their primary function is biostimulation, they have a direct impact on the efficiency of nitrogen and other nutrient use.
Regarding the origin of the biostimulants that are often combined with these biofertilizers, the use of seaweed extracts, humic substances, amino acids, and plant growth-promoting rhizobacteria (PGPR) consortia stands out. All of these contribute to improving soil structure, water retention, chemical fertility, and the plants' ability to absorb and utilize available nitrogen more effectively.
The intelligent combination of these types of products allows for the design of fertilization strategies that not only maintain yield but enhance it, while reducing environmental impact and dependence on external inputs.
With all of the above, the role of biofertilizers in achieving a more efficient use of nitrogen is quite clear: they are the piece that connects soil fertility, microbiology and crop nutrition , allowing for more profitable and sustainable production, with more vibrant soils, better nourished plants and agricultural systems better prepared for the water, climate and market challenges that are already upon us.
