Enhancing Nitrogen Use Efficiency: Insights from the FAO 2025 Report on Sustainable Agrifood Systems
Introduction
Nitrogen (N) is a fundamental nutrient for plant growth and a cornerstone of agricultural productivity. However, its management in cropping systems presents significant challenges. While nitrogen use has increased food security globally, today, reactive N has been identified as one of the top five emerging threats facing humanity and the planet due to its impact on the climate, environment, and public health—and is attributed to the global reliance on reactive N for food production.
Farmers can no longer increase the use of nitrogen fertilizers in their crops to push the plants to produce more. Improving the nitrogen use efficiency (NUE) of crop plants is vital to achieving sustainable agrifood systems that balance productivity and environmental stewardship. There have been many scientific contributions on the topic of NUE, predominately focused on how to improve crop NUE via agricultural management or breeding innovations.
Below, we are presenting some key insights from the FAO report "Sustainable Nitrogen Management in Agrifood Systems," presented on the 20th of January 2025. You can find the full document online on the FAO site. This report will provide a comprehensive overview of the challenges and opportunities related to nitrogen use in agrifood systems. The report explores solutions to enhance nitrogen use efficiency in crop and animal production and elaborates on the magnitude, sources, and pathways of nitrogen flows and losses and associated environmental impacts such as eutrophication, acidification, and biodiversity loss. The report suggests sector-specific approaches to enhance nutrient use efficiency, including adopting circular bioeconomy practices and policy recommendations to promote sustainable nitrogen management. This brief version summarizes the main messages, key actions, and policy options for sustainable nitrogen management in agrifood systems.
Defining Nitrogen Use Efficiency – What is NUE?
Nitrogen Use Efficiency (NUE) measures the proportion of nitrogen inputs that are converted into agricultural outputs, such as crop biomass or yield.
In cropping systems
- Inputs include synthetic fertilizers, organic manure, biological nitrogen fixation, and atmospheric deposition.
- Outputs typically consist of harvested nitrogen in crops, with additional losses occurring through leaching, runoff, volatilization, and erosion.
High NUE indicates efficient nitrogen use, minimizing environmental losses while maintaining productivity.
Conversely, low NUE reflects inefficiencies that result in significant nitrogen losses and associated environmental impacts.
The European Nitrogen Experts Panel introduced a two-dimensional framework for NUE, which balances productivity and environmental impact. This approach defines a "Characteristic Operating Space (COS)," a range where nitrogen inputs optimize yields without significant environmental risks. Values above 90% NUE risk soil nitrogen mining, while values below 50% indicate excessive pollution.
Global Trends and Patterns of NUE
Crop nitrogen use efficiency (NUE) is influenced by environmental factors, plant physiological activity, and their interactions. Nitrogen transformations in soil are dynamic and continuously changing, with biochemical fluxes being the main constraints to NUE. Physical nitrogen losses, such as ammonia volatilization, nitrate leaching, and runoff of soluble forms, further reduce NUE. Temperature and precipitation changes significantly impact biological and enzyme activity, which are crucial for these transformations.
Breeding for nitrogen use efficiency
The efforts of the breeders to create new varieties with enhanced Nitrogen Use Efficiency have been focusing on:
- Root System Optimization: Breeding efforts focus on improving root architecture to enhance nitrogen uptake. Traits like deeper roots, increased root density, and greater lateral root development allow crops to access nitrogen more efficiently from the soil.
- Nitrogen Metabolism Efficiency: Developing varieties with improved biochemical pathways for nitrogen assimilation and utilization can increase NUE. This includes enhancing the activity of enzymes like nitrate reductase and glutamine synthetase, which play critical roles in nitrogen metabolism.
- Stress Resilience: Nitrogen uptake and utilization are highly affected by environmental stresses (e.g., drought, heat). Breeding stress-tolerant varieties ensures better NUE under variable and challenging growing conditions, maintaining productivity with lower nitrogen inputs.
Global NUE has fluctuated over the past decades and has been influenced by regional practices, socioeconomic factors, and technological advancements. In 2022, global crop yield averaged 65 kg N/ha/year, with NUE at approximately 56%. However, significant regional disparities exist:
- High-Yield, Low-NUE Regions: Western Europe and parts of Southeast Asia exhibit high nitrogen inputs but low efficiency, leading to substantial nitrogen losses.
- Low-Yield, High-NUE Regions: Sub-Saharan Africa and parts of Western Asia show limited nitrogen inputs, resulting in high NUE but often at the expense of soil fertility and long-term sustainability.
- Moderate-Yield, Moderate-NUE Regions: These include parts of Latin America and Eastern Europe, where balanced practices yield moderate efficiency.
The relationship between NUE and yield often follows a U-shaped curve, with early agricultural intensification reducing NUE due to overapplication of fertilizers. Advanced economies later improve NUE through technology and regulatory measures.
Challenges in Enhancing NUE
Several challenges obstruct the enhancement of NUE in crop systems:
- Overuse of Synthetic Fertilizers: In regions with high fertilizer subsidies or intense cropping systems, overapplication results in diminished returns and environmental degradation.
- Soil Health Degradation: Depleted soils in low-input systems lack the organic matter necessary for efficient nutrient cycling, leading to low yields and declining fertility.
- Climate Variability: Extreme weather events disrupt nitrogen uptake and exacerbate losses through volatilization and leaching.
- Knowledge Gaps: Farmers often lack access to information or training on best practices for nitrogen management, particularly in low-income regions.
Strategies to Improve NUE
Improving NUE requires a combination of technological innovation, better management practices, and policy support. Key strategies include:
1. 4Rs Nutrient Stewardship
The 4Rs framework—Right Source, Right Rate, Right Time, Right Place—optimizes fertilizer application to match crop needs and minimize losses. For example:
- Right Source: Using enhanced-efficiency fertilizers, such as coated urea, reduces volatilization. Slow- or controlled-release fertilizers can also help reduce the nitrogen leaching in the soil and provide the crop with the N needed for a longer period of time in the right developmental stages.
- Right Rate: Precision agriculture technologies enable farmers to apply nitrogen based on real-time crop requirements. This data can be used to form a customized fertigation schedule (in cases where this is possible to be applied) for improved efficiency.
- Right Time: Splitting nitrogen applications across growing seasons aligns availability with crop demand. Farmers should not apply all nitrogen fertilizers at the start of the season (e.g. before or during sowing), but instead split the amount on 2-5 applications based on the crop needs, the type of fertilizes used and the environmental conditions (e.g. rainfalls).
- Right Place: Targeted application methods, such as banding fertilizers near plant roots, improve uptake efficiency. The application of fertilizers via a drip irrigation system can offer maximum efficiency and minimum nutrient losses if planned correctly.
2. Integrated Crop Management
Incorporating crop rotation and intercropping systems with legumes can enhance nitrogen fixation and reduce reliance on synthetic inputs. Agroforestry and silvopastoral systems also improve nutrient cycling and soil health. FAO experts highlight the importance of using organic nitrogen fertilizers to enhance sustainability. At the same time, it is essential to train livestock farmers to adopt best manure management practices.
3. Precision Agriculture
Remote sensing, soil testing, and data-driven tools provide insights into soil fertility and crop nutrient needs. These technologies enable site-specific management, reducing nitrogen inputs while maintaining yields.
4. Technological Innovations
Emerging technologies, such as nano-fertilizers, slow-release formulations, and bio-stimulants, enhance nitrogen availability and uptake. These innovations minimize environmental losses while maximizing crop productivity.
5. Circular Bioeconomy Principles
Recycling nitrogen within agrifood systems—such as efficiently managing crop residues and utilizing manure—reduces the need for external inputs. For instance, integrating crop-livestock systems allows efficient use of manure as organic fertilizer. At the same time, FAO highlights the importance of reducing food waste and loss at all stages of the agrifood system and promotes the recycling and treatment of food unsuitable for human consumption as livestock feed.
Regional Case Studies
1. Western Europe
Regulatory frameworks like the Nitrates Directive have driven improvements in NUE by limiting fertilizer application rates and promoting best practices. For instance, farmers in the Netherlands use precision farming techniques to maintain high yields with reduced nitrogen inputs.
2. Sub-Saharan Africa
Here, low access to synthetic fertilizers and poor soil fertility challenge productivity. Programs promoting organic amendments, such as compost and biochar, have shown promise in improving NUE while restoring soil health.
3. Asia
Countries like India and China face significant NUE challenges due to the overapplication of fertilizers driven by subsidies. Precision agriculture initiatives, such as China's "Green Fertilizer Project," aim to reduce inputs while maintaining food security.
Environmental and Economic Benefits
Enhancing NUE offers multiple benefits:
- Environmental Gains: Reduced nitrogen losses mitigate eutrophication, air pollution, and greenhouse gas emissions. Improved practices also conserve biodiversity by minimizing ecosystem disruptions.
- Economic Savings: Efficient nitrogen use lowers input costs for farmers while maintaining or increasing yields.
- Climate Resilience: Healthy soils with balanced nitrogen levels retain moisture and nutrients, improving resilience to climate extremes.
Key Policy Recommendations
Governments and stakeholders play a critical role in advancing NUE through:
- Incentives and Subsidies: Support for precision agriculture technologies and enhanced-efficiency fertilizers can accelerate adoption.
- Education and Training: Farmer field schools and extension services should focus on sustainable nitrogen management.
- Research and Development: Investments in innovative nitrogen management solutions are crucial for long-term progress.
- Regulatory Measures: Policies limiting excessive fertilizer use and promoting integrated nutrient management can drive widespread improvements.
Conclusion
Nitrogen use efficiency is a critical metric for sustainable agriculture. By adopting innovative practices and policies, cropping systems can achieve higher productivity while minimizing environmental impacts. A concerted effort from farmers, researchers, and policymakers is essential to transform nitrogen management and ensure food security for future generations.
Further reading
You can find the full report on "Sustainable Nitrogen Management in Agrifood Systems" online in the site of FAO.
https://pmc.ncbi.nlm.nih.gov/articles/PMC10151540/
https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.637108/full
https://pmc.ncbi.nlm.nih.gov/articles/PMC9208628/
Digital Soil Mapping: Boosting West Africa’s Agriculture
Biostimulants in Sustainable Agriculture: An Overview of Their Role and Importance
The Importance of Nitrogen for Plant Growth
Key Practices for Effective Nutrient Management in Organic Farming
Urea and Slow Release Fertilizers: Importance and Best Use Practices
Nitrogen fixation: definition, process, and importance for agriculture
