Realistic nitrogen use efficiency goals in dairy production systems: a review and case study examples

Cecile A.M. de Klein1, Ross M. Monaghan1, Marta Alfaro2, Cameron Gourley3, Oene Oenema4, J. Mark Powell5

1 AgResearch Invermay, Puddle Alley, Mosgiel 9053, New Zealand

2 INIA Remehue, Casilla 24-O, Osorno, Chile

3 Department of Economic Development, Jobs, Transport and Resources, 1301 Hazeldean Road, Ellinbank Victoria 3821.

4 Wageningen University, Alterra, PO Box 47, NL-6700 Wageningen, Netherlands

5 USDA-Agricultural Research Service, U.S. Dairy Forage Research Center, Madison, Wisconsin, 53706, USA


Nitrogen use efficiency (NUE), the ratio between N outputs in products over N inputs, is often used to evaluate N use outcomes of an agricultural system and/or the risk of environmental N losses. In this paper we address the question what NUE goals are realistic for dairy production systems. We use the following definitions of NUE: Crop NUE, defined as the percentage of the total N inputs taken up by crops or pasture; Animal NUE, defined as the percentage of total feed N intake incorporated into milk and meat; and Whole farm NUE, defined as the percentage of total N inputs to the farm that is exported in animal products and/or exported feed. Nitrogen surpluses (i.e. N inputs minus N outputs) are also reviewed. Published values of Crop NUE and N surplus generally ranged between 55-90% and 25-230 kg N/ha/year, respectively, while commonly reported Animal NUE and N surplus values ranged between 15-35% and 110-450 kg N/ha/year. Whole farm NUE and N surplus values ranged between 10-65% and 40-700 kg N/ha/year. In a NZ catchment study, Whole farm NUE was affected more strongly by differences between catchments (e.g. soil and climatic conditions) than by differences in management. In contrast, N surplus values differed both between-catchment and within-catchment and were good indicators of N losses to water. Realistic goals for NUE will therefore depend on the agro-climatic context in which a dairy system operates and on the economic and environmental goals the system aims to achieve. Crop and Animal NUE values can be valuable indicators for optimising fertiliser and feed use, and minimizing N losses. However, global or even national Whole-farm NUE values appear to be of limited value if the ultimate goal for setting targets is to reduce the environmental impact of N use. Whole-farm level targets based on N surplus would be a more useful indicator for this. Regardless of the metric used all metrics are calculated based on estimates of N inputs and N outputs, so it is important to agree on which items should be included in the input and output terms, and that all inputs and outputs are measured or adequately estimated. For systems that import large amounts of purchased feeds, this should include the N inputs required to produce this feed. Any NUE goals targets should be set in the context of other agro-environmental indicators such as losses of phosphorus and faecal organisms to water, carbon footprints, and energy and water use efficiencies.

Nitrogen and cereal production: Opportunities for enhanced efficiency and reduced N losses


 K. Ladha1 and Debashis Chakraborty2

1International Rice Research Institute, Makati city 1226, Philippines,,

2Indian Agricultural Research Institute, New Delhi 110012, India


Presently, 50 percent of the human population relies on synthetic nitrogen (N) fertilizer for food production. In agriculture of subsistence during pre-chemical era, biological N2 fixation (BNF) was the primary source of reactive N but, in recent decades, chemical N fixation (synthetic N) has become more important in global agriculture. Today, synthetic N fertilizer introduces reactive N of over 100 Tg N year-1 into the global environment to increase food production. Although this has sustained the large human population in meeting dietary needs, a large agriculture area in the world still lacks available N to sustain the crop production. This together with a larger growing population obviously means that the future global demand for synthetic N is bound to grow markedly. However, since a substantial amount of N applied for food production is lost to the environment, this has also caused a web of problems causing air and water pollution and contributing to climate change. Unlike nonreactive gaseous N2, reactive N has magnified the adverse effects because the same atom of N can cause multiple effects in the atmosphere, in terrestrial ecosystems, in freshwater and marine systems, and on human health. This paper, while focusing three major cereals (maize, rice and wheat) of global importance, (i) analyses the global consumption and demand for fertilizer N, (ii) evaluates synthetic fertilizer N recovery efficiency and losses, (iii) examines long-term effects of continuous N fertilization on changes in soil N reserves, (iv) constructs global N budgets, and (v) analyses various strategies available to improve the overall use efficiency of N.

Enhanced nitrogen fertilizer technologies support the ‘4R’ concept to optimize crop production and minimize environment losses

Clifford S. Snyder1

1International Plant Nutrition Institute, P.O. Box 10509, Conway, Arkansas, USA 72034,,


Fertilizer nitrogen (N) has been, and will continue to be, essential in nourishing, clothing, and providing bioenergy for the human family. Yet, emissions of ammonia (NH3) and nitrous oxide (N2O), and losses of nitrate-N (NO3-N) to surface and groundwater resources are risks associated with fertilizer N use that must be better managed to help meet expanding societal expectations. Nitrogen fertilizers with polymer coatings, or with addition of urease and/or nitrification inhibitors, or possessing other characteristics that afford them either improved agronomic response and/or lessened loss of N to the environment  – compared to a reference water soluble fertilizer – may be considered enhanced efficiency N fertilizers (EEFs). Agronomic and horticultural research with these technologies has been carried out for many decades, but it has been primarily in the last decade that research has increasingly also measured their efficacy in reducing N losses via volatilization, leaching, drainage, runoff, and denitrification. Expanded use of EEFs, within the concept of 4R N management (right source, right rate, right time, right place) may help increase crop yields while minimizing environmental N losses. Coupling these 4R N management tools with precision technologies, information systems, and crop growth and N utilization and transformation models –especially with weather models, may improve opportunities for refined N management in the future.

Looking forward to 2030: Nitrogen and the Sustainable Development Goals

Achim Dobermann

Rothamsted Research, Harpenden, Herts, AL5 2JQ, UK,


The new Sustainable Development Goals (SDGs) provide a framework for all countries to develop and implement roadmaps for sustainable development in all its dimensions. Agriculture contributes to many of the new SDGs and their Targets. SDG 2 on ending hunger, improving nutrition and achieving a more sustainable agriculture is among the most challenging ones to achieve. Transformative changes will be required in how food is consumed and produced. Nitrogen as the world’s most important nutrient is a key currency for all that, requiring a full-chain approach to increase its overall efficiency and reducing its environmental impact. Agro-food systems in developed as well as developing countries need to become more precise in their management to achieve substantial increases in N use efficiency (NUE). A coherent, well-coordinated effort is needed for monitoring NUE at unprecedented levels of detail, using new sensing and data science technologies that are now becoming available. Many solutions exist, but they will require more investment as well as new ways of working to achieve faster and greater impact. Science should embrace an innovation culture, translating new ideas much faster into commercial technologies and actionable knowledge widely accessible to farmers and businesses along the whole nitrogen chain.

Success stories of nitrogen across two decades of international conferences

Jan Willem Erisman1,2, Enrico Dammers2, James N. Galloway3, Allison M. Leach5, Albert Bleeker4

1 Louis Bolk Institute, Hoofdstraat 24, 3972 LA, The Netherlands

2 VU Amsterdam, The Netherlands

3 Environmental Sciences Department, University of Virginia, Charlottesville VA 22904 USA.
4 PBL Netherlands Environment Assessment Agency, Antonie van Leeuwenhoeklaan 9, 3721MA Bilthoven, The Netherlands

5 Department of Natural Resources and The Sustainability Institute, University of New Hampshire, Durham NH 03824 USA


The first International Nitrogen Conference was held in 1998 in the Netherlands. It was recognized then that nitrogen had grown from a local hotspot problem to an international and even global problem. The main focus of the conference was on scientific developments identifying the major issues related to the human influence on the nitrogen cycle and the potential options to deal with it. At the second Nitrogen Conference it was decided to initiate the International Nitrogen Initiative, and seven focus regions or continents were identified. Now, 18 years after the first conference in the Netherlands, the International Nitrogen Conference has been organized in and by all these seven regions, Oceania being the last in 2016. During these 18 years many developments have taken place and progress has been made on our scientific understanding of the different nitrogen issues, on the assessment of potential indicators and successful measures to address the issue and on the preparation of policies to reduce nitrogen pollution. In this presentation an overview will be given of these achievements using the International Nitrogen Conferences as milestones and showing how they contributed to the achievements.

Economic perspectives on nitrogen in farming systems: managing trade-offs between production, risk and the environment

David J Pannell

University of Western Australia,,


The economics of nitrogen in farming systems are complex, multifaceted, fascinating and sometimes surprising. They span issues at various scales: the field, farm, region, nation and world. Economic insights are crucial for making sound decisions about farm-level management of nitrogen, and also about regional or national policy, such as for water pollution. In this paper I present key insights from a large and important literature that is often neglected by technical scientists. Issues covered include: the economics of nitrogen as an input to production; nitrogen and economic risk at the farm level, including price risk and production risk; the economics of nitrogen fixation by legumes; the existence of flat payoff functions, which often allow wide flexibility in decisions about nitrogen fertilizer rates; explanations for over (or under) application of nitrogen fertilizers by some groups of farmers; farm-level economics of nitrogen-saving technologies; the economics of nitrogen pollution, at both the farm-level and the policy level; and the international market for nitrogen fertilizer. Economics helps to explain farmer behaviour, and to design strategies and policies that are more beneficial and more likely to be adopted and successfully implemented.

Nitrogen budgets – tools to validate information on nitrogen fluxes

Wilfried Winiwarter

Reactive nitrogen compounds, released by anthropogenic activities, may take different pathways in the environment, not all of which are easily traceable. Nitrogen budgets allow using surrogate information for fluxes that otherwise cannot easily be measured or validation of flux quantities for which an independent second set of data can be made available. In order to reliably assess nitrogen budgets and to make them comparable, the harmonization of approaches is required. Such a harmonizing effort has been performed under the European “air quality” convention, the Convention on Long-Range Transboundary Air Pollution. Based on existing efforts to collect data on fluxes of nitrogen compounds, specifically in the framework of the convention, from national greenhouse gas inventories mandatory under UNFCCC, or in connection with European activities of EUROSTAT or OECD, a guidance document has been developed to allow assessing national nitrogen budgets. Eight individual “pools” have been identified that are considered the start- and endpoints of environmental fluxes. The guidance document allows to properly assign and quantify fluxes between pools and cares for a consistent nomenclature. This presentation demonstrates complete and partial applications of the concept, and demonstrates the advantages of harmonizing approaches. It takes available published budgets for several European and non-European countries, analyzes them for compatibility, and evaluates nitrogen budgets for their potential contribution to a sustainable development of agriculture and beyond agriculture. Downscaling national to regional budgets, and comparing to the concept of farm-scale budgets (farm scale as well as soil budgets) will conclude the analysis.

Nitrogen and Cereal Production: Opportunities for Enhanced Nitrogen Use Efficiency and Reduced Losses

 J.K. Ladha

International Rice Research Institute-India


Nitrogen is unique among the major nutrients in that it originates from the atmosphere, and its transformations and transport in an ecosystem are mediated by the water cycle and biological processes. The atmosphere contains a large, well-mixed biologically unavailable pool of nitrogen, of which a small part is converted to biologically available reactive nitrogen. Biological nitrogen fixation is the primary source of reactive nitrogen but, in recent years, chemical nitrogen fixation has become important in increasing crop productivity to alleviate the ever-increasing food insecurity. Since the Green Revolution, the application of nitrogen fertilizers on “modern crop cultivars” of cereals boosted food production by about 6.4% per year. Today, fertilizer nitrogen supplies 100 Tg year-1 for food production. Of this, 50% is applied to three major cereal (maize, rice and wheat). It is projected that annual total global nitrogen use will be around 171 Mt in 2050, assuming no change in nitrogen-use efficiency (NUE). Fertilizer nitrogen-recovery efficiency by cereals is 30% to 50%. The remaining surplus nitrogen is lost to the environment, causing disruptions in ecosystem functions. Much research has been conducted during the past decades to improve NUE by developing fertilizer management strategies based on a better synchronization between the supply and crop deman. This presentation will analyze the (1) different sources of N inputs and outputs in global cereal production, (2) effect of long-term addition of synthetic nitrogen on soil nitrogen storage, (3) NUE for the cereals grown across large agroclimatic regions, (4) strategies available to improve the NUE and reduce losses.

Nitrogen cycling and its environmental impacts on terrestrial ecosystems in China

Yan Xiaoyuan1, Liu Xuejun2

1 Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China

2 College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China


China now creates more nitrogen than any other country in the world. Total nitrogen input to the terrestrial ecosystem of mainland China increased from 25.2 Tg in 1980 to 61.0 Tg in 2010, while the amount of natural N2 fixation changed little during this period (9.3–11.0 Tg). Though large amount of nitrogen input plays a vital role in ensuring food security, it has contributed to low nitrogen use efficiency both in crop and livestock production systems. Much of the remainder nitrogen can be considered an expensive and environmentally damaging waste such as emissions of greenhouse gases, degradation of soil and freshwater. Average bulk nitrogen deposition, plant foliar nitrogen and crop nitrogen uptake from long-term unfertilized croplands all significantly (p<0.05) increased from 1980 to 2010, in agreement with rapidly increased NH3 and NOx emissions. As a consequence, significant soil acidification was reported in major Chinese croplands, grasslands and forestlands. Clear evidence showed that plant species richness and soil bacterial diversity declined with increased nitrogen deposition in temperate grasslands. Meanwhile, large amounts of soil nitrate nitrogen accumulation were observed in major upland soils in China, threatening groundwater quality. Surface water eutrophication, air quality deterioration, both closely linked with reactive nitrogen, are increasingly being witnessed. China is facing a huge challenge to realize food security and protect the environment through maximizing nitrogen use efficiency and minimizing nitrogen negative effects.