Plant Biostimulants and Nutrient Use Efficiency:

Improving Crop Nutrition Without Replacing Fertilizers

What Is Nutrient Use Efficiency?

Nutrient use efficiency describes how effectively a crop acquires and uses nutrients available within a production system.

The concept can be evaluated in several ways depending on the crop, nutrient, and research objective.

At a practical level, NUE asks questions such as:

• How much crop yield is produced from the nutrients supplied?
• How much of an applied nutrient is recovered by the crop?
• How effectively does the plant acquire nutrients from the root zone?
• How efficiently are absorbed nutrients converted into biomass or harvested yield?
• Can the same productivity be maintained with more efficient nutrient management?

These questions demonstrate why NUE is broader than fertilizer application rate.

Two fields receiving the same amount of nitrogen may produce different yields due to differences in soil properties, root development, water availability, nutrient timing, environmental conditions, crop genetics, and management practices.

Improving NUE therefore requires understanding the complete soil–root–plant–fertilizer system.

Why Nutrient Use Efficiency Matters

Fertilizer represents a significant production input in many agricultural systems.

When nutrients are not effectively captured and utilized by crops, growers may lose part of the economic value of their fertilizer investment.

Nutrient losses can also contribute to environmental problems.

Depending on the nutrient and production system, these may include:

• Nitrate leaching
• Ammonia volatilization
• Nitrous oxide emissions
• Phosphorus runoff
• Surface-water eutrophication
• Nutrient accumulation or imbalance in soils

Improving NUE can therefore serve several objectives simultaneously:

• Agronomic efficiency: supporting crop productivity.
• Economic efficiency: obtaining greater value from fertilizer inputs.
• Resource efficiency: making better use of finite or energy-intensive nutrient resources.
• Environmental management: reducing avoidable nutrient losses.

The objective is not simply to minimize fertilizer use.

Applying too little fertilizer can reduce yield and crop quality and decrease nutrient removal from the field.

The goal is to better match nutrient supply to crop demand and improve the efficiency of the complete nutrition system.

Where Do Plant Biostimulants Fit?

The European Union's Fertilizing Products Regulation provides an important framework for understanding this relationship.

Under Regulation (EU) 2019/1009, a plant biostimulant stimulates plant nutrition processes independently of the product's nutrient content with the aim of improving one or more specified characteristics.

One of those characteristics is:

Nutrient use efficiency.

Other recognized functions include:

• Tolerance to abiotic stress
• Crop-quality traits
• Availability of confined nutrients in the soil or rhizosphere

This definition establishes an important distinction.

A fertilizer primarily supplies nutrients.

A biostimulant acts on processes associated with plant nutrition or the plant–rhizosphere system.

The two categories can therefore perform complementary rather than interchangeable functions.

Fertilizer Supply vs. Nutrient Efficiency

Consider a crop requiring nitrogen.

A nitrogen fertilizer such as urea, ammonium nitrate, ammonium sulfate, CAN, or an appropriate NPK formulation provides nitrogen to the production system.

A biostimulant does not remove the crop's biological requirement for nitrogen.

Instead, depending on the product and growing conditions, a biostimulant may influence processes associated with:

• Root development
• Nutrient uptake
• Nutrient transport
• Nutrient assimilation
• Rhizosphere activity
• Plant metabolism
• Physiological responses to environmental stress

This leads to a useful distinction:

Fertilizer supplies nutrients.

Biostimulants may help optimize processes associated with obtaining and using those nutrients.

This is why the two should normally be considered as part of an integrated crop-nutrition strategy rather than as competing inputs.

How Can Biostimulants Influence Nutrient Use Efficiency?

There is no single mechanism shared by every biostimulant.

Seaweed extracts, humic substances, protein hydrolysates, microbial biostimulants, amino-acid formulations, and other products differ substantially in composition and biological activity.

Their influence on nutrient efficiency can therefore occur through different pathways.

Root-System Development

Roots determine the volume of soil that a crop can explore for nutrients and water.

A larger or more effective root system may improve the plant's ability to access nutrients distributed throughout the root zone.

Certain biostimulants have been associated with changes in:

• Root length
• Lateral root formation
• Root branching
• Root biomass
• Root architecture
• Root-hair development

These responses can potentially increase the interface between the plant and soil.

However, greater root biomass alone does not automatically prove improved NUE.

The relevant question is whether the root response ultimately leads to improved nutrient acquisition, crop performance, or fertilizer efficiency under actual production conditions.

Nutrient Uptake and Transport

After nutrients reach the root surface, they must be absorbed and transported within the plant.

Research on several biostimulant categories has investigated effects on nutrient transporters, membrane processes, root physiology, and metabolic pathways associated with nutrient uptake.

The response depends strongly on:

• Biostimulant type
• Formulation
• Crop species
• Nutrient status
• Dose
• Application method
• Environmental conditions

A product that influences nitrogen acquisition in one crop cannot automatically be assumed to produce the same response for phosphorus, potassium, or micronutrients in another crop.

Product-specific and crop-specific evidence remains important.

Rhizosphere Interactions

The rhizosphere is the biologically active zone surrounding plant roots.

Nutrients present in soil are not necessarily immediately available for plant uptake.

Their availability can be affected by:

• Soil pH
• Mineral composition
• Organic matter
• Moisture
• Microbial activity
• Root exudates
• Chemical reactions within the soil

Certain microbial biostimulants interact directly with this environment.

Depending on the microorganism, these interactions may influence nutrient mobilization, root development, or plant–microbe relationships.

Other biostimulants may indirectly affect rhizosphere processes by altering root growth or root exudation.

The result is an important principle:

Nutrient efficiency depends not only on how much nutrient is present, but also on whether that nutrient is accessible to the crop.

Nitrogen Use Efficiency

Nitrogen is one of the most important nutrients in global crop production and a major focus of NUE research.

Plants require nitrogen for proteins, enzymes, chlorophyll, nucleic acids, and numerous metabolic processes.

However, nitrogen in agricultural systems can also be lost through several pathways.

Depending on fertilizer form, soil, weather, and management, losses may occur through:

• Ammonia volatilization
• Nitrate leaching
• Denitrification
• Runoff
• Nitrous oxide emissions

Biostimulant research on nitrogen has examined potential effects on root development, nitrogen uptake and assimilation, plant metabolism, and microbial interactions.

But biostimulants represent only one possible component of nitrogen-efficiency management.

Other important tools include:

• Appropriate nitrogen rate
• Correct fertilizer source
• Split application
• Appropriate placement
• Irrigation management
• Soil testing
• Tissue analysis
• Urease inhibitors, where appropriate
• Nitrification inhibitors, where appropriate
• Controlled- or slow-release fertilizers, where appropriate
• Precision nutrient management

A biostimulant should therefore complement—not replace—sound nitrogen management.

Phosphorus Use Efficiency

Phosphorus behaves differently from nitrogen.

Rather than being highly mobile under most soil conditions, phosphorus can become strongly associated with soil minerals and chemical compounds, limiting its availability to plants.

Phosphorus availability is influenced by factors including:

• Soil pH
• Calcium
• Iron and aluminum chemistry
• Soil mineralogy
• Organic matter
• Root activity
• Microbial processes

Some microbial products are investigated for their ability to influence phosphorus availability through processes such as solubilization.

Arbuscular mycorrhizal fungi can also extend the effective nutrient-exploration network associated with plant roots and may contribute to phosphorus acquisition under suitable conditions.

However, these biological processes do not mean that phosphorus fertilizer is universally unnecessary.

Where soil phosphorus supply is insufficient to meet crop demand, appropriate phosphorus nutrition remains essential.

Potassium Use Efficiency

Potassium performs numerous physiological functions in plants.

It contributes to processes including:

• Stomatal regulation
• Water relations
• Enzyme activation
• Carbohydrate transport
• Osmotic regulation
• Crop quality
• Stress response

Soils may contain substantial total potassium, while only a fraction is immediately available to plants.

Biostimulant strategies aimed at potassium efficiency may involve improved root development, nutrient acquisition, plant physiological processes, or rhizosphere interactions.

As with nitrogen and phosphorus, the effect must be evaluated in the context of the underlying potassium management program.

A biostimulant cannot compensate indefinitely for an inadequate potassium supply where crop removal exceeds available soil and fertilizer inputs.

Micronutrient Efficiency

Micronutrients are required in much smaller quantities than nitrogen, phosphorus, or potassium, but they remain essential for plant metabolism.

Important micronutrients include:

• Iron
• Zinc
• Manganese
• Copper
• Boron
• Molybdenum

Their availability can be strongly affected by soil pH, organic matter, moisture, carbonate content, redox conditions, and interactions with other nutrients.

Root development and rhizosphere activity may therefore influence micronutrient acquisition.

However, a confirmed micronutrient deficiency should be diagnosed and treated appropriately.

A biostimulant should not be used to avoid supplying an essential nutrient when the crop genuinely lacks it.

The Role of Different Biostimulant Categories

Different biostimulant groups may interact with nutrient efficiency through different mechanisms.

Humic and Fulvic Substances

Humic substances are associated with soil and root processes and have been investigated for their influence on root development, nutrient acquisition, and plant metabolism.

Their performance can depend on the raw material source, extraction process, composition, dose, soil conditions, and crop.

Seaweed Extracts

Seaweed-derived products contain complex mixtures of bioactive compounds.

Research has linked certain formulations to changes in root development, plant metabolism, nutrient acquisition, and responses to abiotic stress.

Their effects should not be attributed simply to the mineral nutrients contained in the extract.

Protein Hydrolysates

Protein hydrolysates contain a mixture of peptides and amino acids generated by protein hydrolysis.

Studies have investigated their effects on root development, nitrogen metabolism, nutrient uptake, and physiological processes.

Raw-material source and hydrolysis technology can strongly influence product characteristics.

Microbial Biostimulants

Beneficial microorganisms may influence nutrient acquisition through interactions with roots and the rhizosphere.

Their performance is particularly dependent on biological conditions, as the microorganisms must remain viable and interact effectively with the production environment.

Amino-Acid-Based Products

Amino acids participate in numerous metabolic pathways.

Commercial formulations vary widely, however, and their effects cannot be predicted simply from the total percentage of amino acids printed on a label.

Can Biostimulants Reduce Fertilizer Requirements?

Potentially—but this claim requires careful interpretation.

Research increasingly examines whether biostimulants can maintain crop performance under reduced nutrient-input conditions.

Recent reviews report promising results for several biostimulant categories and crops, particularly regarding nutrient use efficiency.

However, responses are not universal.

Results can depend on:

• Crop
• Soil
• Climate
• Nutrient status
• Product formulation
• Application timing
• Dose
• Fertilizer program
• Experimental conditions

Therefore, the statement:

"Biostimulants reduce fertilizer requirements"

is too broad when presented without supporting evidence.

A more scientifically defensible approach is:

Some biostimulants may improve nutrient use efficiency sufficiently to support optimization of fertilizer inputs under specific crop and production conditions.

Any reduction in fertilizer rate should be validated through appropriate field trials, nutrient analysis, yield measurements, and economic evaluation.

Why Simply Cutting Fertilizer Can Be Risky

Suppose a grower normally applies a nutrient program designed to meet expected crop demand.

Introducing a biostimulant and immediately reducing fertilizer by 30% without field evidence creates an uncontrolled agronomic experiment.

If nutrient supply falls below crop requirements, potential consequences include:

• Reduced biomass
• Lower yield
• Poorer crop quality
• Nutrient deficiency
• Reduced stress tolerance
• Lower economic return

The correct sequence is different.

First, establish the baseline fertilizer program.

Then evaluate the biostimulant.

Measure crop response.

If evidence demonstrates improved nutrient efficiency, carefully test alternative nutrient rates.

This converts a marketing assumption into an agronomic decision.

Measuring Nutrient Use Efficiency in Field Trials

Claims about improved NUE should ideally be supported by measurable evidence.

A simple commercial trial might include:

Treatment A — Standard fertilizer program

Treatment B — Standard fertilizer program + biostimulant

Treatment C — Reduced fertilizer program

Treatment D — Reduced fertilizer program + biostimulant

This type of design can help distinguish between several questions:

Does the biostimulant improve performance at the standard nutrient rate?

Does reducing fertilizer decrease crop performance?

Can the biostimulant help maintain performance at the tested reduced nutrient rate?

Does the combination produce an economically meaningful result?

Measurements can include:

• Marketable yield
• Total yield
• Plant nutrient concentration
• Nutrient uptake
• Crop quality
• Root development
• Fertilizer input
• Treatment cost
• Revenue
• Return on investment

Where possible, trials should be replicated and statistically evaluated.

Nutrient Efficiency Is Not the Same as Yield

Yield is important, but it does not provide the complete picture.

Imagine two treatments producing the same yield.

Treatment A requires a higher nutrient input.

Treatment B produces the same yield with a lower nutrient input.

Treatment B may have higher nutrient-use efficiency.

Now consider another situation.

Treatment C produces a higher yield but also receives substantially more fertilizer.

Its yield is higher, but its efficiency per unit of nutrient applied may not necessarily be better.

This is why nutrient-efficiency claims should specify what is actually being measured.

Environmental Stress Can Change Nutrient Efficiency

Crop nutrition does not operate independently of environmental conditions.

Drought, salinity, excessive heat, cold, waterlogging, and other abiotic stresses can alter:

• Root growth
• Nutrient movement through soil
• Nutrient uptake
• Transpiration
• Photosynthesis
• Plant metabolism

This creates an important connection between two recognized biostimulant functions:

Nutrient use efficiency and tolerance to abiotic stress.

A crop with impaired root activity during drought may have difficulty acquiring nutrients even when those nutrients are present in the soil.

Certain biostimulants may support physiological responses under moderate stress, potentially helping the plant maintain processes associated with nutrient acquisition and utilization.

However, biostimulants cannot compensate for severe agronomic failures such as prolonged absence of irrigation.

Fertigation and NUE

Fertigation provides an opportunity to synchronize nutrient supply more closely with crop demand.

When properly managed, growers can adjust:

• Nutrient concentration
• Application frequency
• Nutrient ratios
• Timing
• Irrigation volume

Biostimulants compatible with fertigation systems may be incorporated into such programs where technically appropriate.

Compatibility must be checked carefully.

Potential problems include:

• Precipitation
• pH changes
• Clogged emitters
• Reduced microbial viability
• Chemical incompatibility

Biostimulants should never be added to fertilizer tanks simply because both products are intended for crop nutrition.

Product-specific compatibility should be verified first.

Foliar Biostimulants and Nutrient Programs

Some biostimulants are applied through foliar sprays rather than through the root zone.

This may be useful when the intended physiological effect is associated with plant tissues or when application timing corresponds to a particular growth stage or stress event.

However, foliar biostimulants should not automatically be confused with foliar fertilizers.

A foliar fertilizer supplies nutrients through leaf surfaces.

A foliar biostimulant is intended primarily to stimulate physiological or nutritional processes independently of its nutrient content.

Some commercial products may contain both nutritional and biostimulant components, making careful evaluation of labels and formulations important.

Combining Biostimulants with Precision Agriculture

The future of NUE management is likely to become increasingly data-driven.

Precision-agriculture systems can provide information from:

• Soil analysis
• Tissue analysis
• Yield maps
• Satellite imagery
• Drone imagery
• Weather data
• Soil-moisture sensors
• Electrical conductivity mapping
• Crop models

These tools can help identify spatial and temporal differences in nutrient demand.

Biostimulants could eventually be integrated into these systems more precisely.

Instead of applying the same product across every field on a fixed schedule, growers may increasingly identify where a specific physiological or nutrient-efficiency intervention is most likely to produce value.

Product Quality Still Matters

The term "biostimulant" encompasses a wide range of products.

Two products belonging to the same category may have substantially different compositions and performance.

When evaluating products intended to improve NUE, growers and distributors should consider:

• Raw-material source
• Manufacturing process
• Active components
• Product characterization
• Stability
• Recommended dose
• Application method
• Storage conditions
• Crop-specific evidence
• Field-trial data
• Regulatory claims

For microbial products, additional considerations include strain identification, viable microorganism concentration, shelf life, and storage requirements.

A broad claim such as "improves nutrient uptake" should not be accepted without examining the evidence supporting it.

Avoiding Misleading NUE Claims

As interest in fertilizer efficiency grows, nutrient-use efficiency can easily become a marketing phrase rather than a measurable agronomic concept.

Claims such as:

"Use 50% less fertilizer"

"Replace NPK"

"Eliminate phosphorus fertilizer"

Or

"Unlock all nutrients in the soil"

It should be treated cautiously unless supported by appropriate evidence for the specific product, crop, soil, and application program.

Nutrient management is governed by mass balance.

Crops remove nutrients from production systems.

Those nutrients ultimately need to come from soil reserves, organic inputs, biological processes where applicable, fertilizer inputs, or a combination of these sources.

Biostimulation can potentially improve efficiency.

It cannot eliminate the fundamental nutrient requirements of plants.

Building an Integrated Nutrient-Efficiency Program

A practical NUE strategy can be summarized as:

Measure → Diagnose → Supply → Optimize → Stimulate → Monitor → Adjust

Measure

Use soil, water, and tissue analysis where appropriate.

Diagnose

Identify actual nutrient constraints rather than assuming that every growth problem is nutritional.

Supply

Provide adequate essential nutrients according to crop demand and production conditions.

Optimize

Improve fertilizer source, rate, timing, and placement, as well as irrigation and other management factors.

Stimulate

Where supported by evidence, introduce an appropriate biostimulant for a defined agronomic objective.

Monitor

Measure crop response, nutrient status, yield, and quality.

Adjust

Modify the program according to measured results rather than marketing expectations.

This framework places biostimulants in their appropriate position:

As one tool within an integrated crop-nutrition system.

Economic Evaluation of NUE

A biological response is not enough.

The grower ultimately needs an economically useful response.

Consider a biostimulant program that costs USD 40 per hectare.

If it improves nutrient efficiency but produces no measurable increase in yield, quality, fertilizer savings, or other economically valuable outcomes, the biological effect may have limited commercial value.

Conversely, a treatment that allows a carefully validated reduction in fertilizer input while maintaining yield could potentially generate measurable savings.

The appropriate calculation depends on the objective.

A simplified comparison is:

Net Benefit = Additional Revenue + Validated Input Savings − Treatment Cost

Then:

ROI (%) = Net Benefit ÷ Treatment Cost × 100

Any claimed fertilizer savings should be demonstrated rather than assumed.

The Future of Biostimulants and Nutrient Efficiency

Nutrient use efficiency is likely to remain one of the most important areas of biostimulant research.

Recent scientific reviews continue to report potential improvements in nutrient acquisition and utilization from multiple biostimulant categories while also emphasizing the need for more standardized measurements, appropriate controls, and trials under both adequate and reduced nutrient conditions.

Future research may increasingly connect biostimulants with:

• Precision fertilization
• Sensor-based crop monitoring
• Microbiome management
• Controlled-release fertilizers
• Enhanced-efficiency fertilizers
• Variable-rate nutrient application
• Predictive crop models
• Artificial intelligence
• Advanced biological formulations

The most important development may not be a single new product.

It may be the ability to identify which biostimulant works, for which crop, under which nutrient conditions, at what application rate, and with what measurable economic return.

Conclusion

Plant biostimulants offer a promising approach to improving nutrient use efficiency, but their role must be understood correctly.

They do not eliminate crop nutrient requirements.

They do not automatically replace fertilizers.

And applying a biostimulant does not automatically justify reducing inputs of nitrogen, phosphorus, potassium, or micronutrients.

Instead, selected biostimulants may influence root development, nutrient acquisition, rhizosphere interactions, nutrient transport, plant metabolism, and other processes associated with crop nutrition.

Their greatest value is therefore likely to emerge when they are integrated with sound fertilizer management rather than positioned against it.

For growers, the practical approach is clear:

• Diagnose nutrient requirements.
• Build an appropriate fertilizer program.
• Identify opportunities to improve efficiency.
• Select a biostimulant supported by relevant evidence.
• Test it under local conditions.
• Measure nutrient response and crop performance.
• Calculate the economic return.

The future of crop nutrition is not simply about applying more fertilizer or replacing fertilizer with biological products.

It is about producing more efficiently from every unit of nutrient, water, land, and agricultural input available to the crop.

References

1. European Parliament and Council (2019). Regulation (EU) 2019/1009 — EU Fertilizing Products Regulation. Official EUR-Lex Regulation
2. du Jardin, P. (2015). Plant biostimulants: Definition, concept, main categories, and regulation. Scientia Horticulturae, 196, 3–14.
3. Rouphael, Y. & Colla, G. (2020). Editorial: Biostimulants in Agriculture. Frontiers in Plant Science, 11, 40.
4. Calvo, P., Nelson, L. & Kloepper, J.W. (2014). Agricultural uses of plant biostimulants. Plant and Soil, 383, 3–41.
5. Quille, P. et al. (2025). Reducing fertilizer inputs: plant biostimulants as an emerging strategy to improve nutrient use efficiency. Discover Sustainability, 6, 128.
6. Basar, N.U., Shahid, M.A., San Bautista Primo, A. & Kadyampakeni, D.M. (2025). Synergies between biostimulants and plant nutrients: a review of eco-friendly nutrient management in crop production. Discover Agriculture, 3, 150.
7. Van Oosten, M.J., Pepe, O., De Pascale, S., Silletti, S. & Maggio, A. (2017). The role of biostimulants and bioeffectors in alleviating abiotic stress in crop plants. Chemical and Biological Technologies in Agriculture, 4, 5.
8. Colla, G., Rouphael, Y., Canaguier, R., Svecova, E. & Cardarelli, M. (2014). Biostimulant action of a plant-derived protein hydrolysate produced through enzymatic hydrolysis. Frontiers in Plant Science, 5, 448.