The Next Generation of Nitrogen Management in Food Production Systems
Nitrogen (N) is an essential element for all living organisms. Its use in agriculture is key to nourishing a growing human population. However, only about 50% of the N added to croplands is recovered in harvested crop products, most of which is fed to livestock and poultry, and only about 16% ends up in crop and animal products for human consumption. Overall, the use of synthetic N fertilizers has been a tremendous boon for human nutrition and health, but the inefficiencies in food production systems have led to losses of N to water and air, leading to numerous unsustainable environmental and human health impacts, including significant contributions to climate change, stratospheric ozone depletion, drinking water contamination, harmful algal blooms, and respiratory illnesses.
Current efforts to improve N efficiency in agriculture focus largely on the “4R” concept of nutrient stewardship -- application of nutrients with the right rate, right type, right time, and right placement. Expansion of a variety of best management practices, such as adopting enhanced efficiency fertilizers, conservation tillage, cover crops, and improved irrigation management, can also improve N use efficiency. These approaches and other on-going innovations are making important incremental contributions to reducing N pollution in air and water, but they face challenges of variable effectiveness by locale, socio-economic barriers to widespread adoption, and lack of a more comprehensive systems approach to decoupling food production from nitrogen losses to the environment.
We envision a transformation of the current, mostly linear and “leaky” system of N use in agriculture to one that is more circular, targeted, and efficient, thus cutting polluting N losses by half while also ensuring the high productivity needed to meet growing human needs for healthy diets and food security. Emanating from an interdisciplinary workshop of thirty eminent agronomists, geneticists, soil scientists, livestock specialists, biogeochemists, biotechnologists, economists, ecologists, and modelers (see list below), held at the Banbury Center of the Cold Springs Harbor Laboratory in April 2024, we call this new vision Nitrogen2.0.
For most of human history, farmers relied on natural sources of N to grow crops, such as the natural soil fertility and manure additions, which we call Nitrogen0.0. As populations rose in the 19th century, this system was inadequate to meet food demands. Early 20th century discoveries led to Nitrogen1.0– large-scale production of synthetic N fertilizers, which revolutionized agriculture and greatly improved human nutrition and food security. However, this has led to unsustainable N losses to air as ammonia, nitrogen oxides, and nitrous oxide and to water as nitrate and dissolved organic nitrogen. Specialization and intensification of agriculture led to separation of crop and animal production, uncoupling manure production from recycling and leading to more nitrogen losses. Consequently, two-thirds of U.S. coastal ecosystems, one-third of streams, and two-fifths of lakes are impaired by nitrogen and phosphorus pollution; 1.4 million people rely on well water in areas where groundwater nitrate concentrations exceed drinking water standards; and over 100,000 premature deaths are attributed annually to air pollution from nitrogen oxides, ammonia, and fine particulates. Nitrous oxide, emitted mostly from agricultural soils, contributes 6% of global radiative forcing and is the most abundantly emitted stratospheric ozone depleting substance. Mitigating these impacts while maintaining agricultural productivity remains a significant challenge for the 21st century.
Enter Nitrogen2.0 – a new era of N management that is more circular, targeted, and efficient, thus enabling high productivity while significantly reducing environmental impacts. This re-imagining of the crop and livestock systems through technological development and management innovation could cut N losses to air and water by half while maintaining the productivity needed for human nutrition and food security. Increased fertilizer use efficiency can also reduce costs and improve profits.
These three components—increased non-crop-N in livestock feed, improved efficiencies through crop breeding and management, and improved manure management and recycling—will each make major contributions to reduce N losses on their own, and they synergize to advance a more sustainable and circular food production system. The Nitrogen2.0 transformative vision is consistent with, but goes well beyond, currently available measures to improved nitrogen management, such as implementation of the “4Rs” of nutrient stewardship (application of nutrients with the right rate, right type, right time, and right placement), enhanced efficiency fertilizers, other soil amendments, conservation tillage, cover crops, and other concepts of regenerative agriculture. It is not mutually exclusive with other possible technological breakthroughs, such as genetic modification for biological N fixation in grains or development of high yielding perennial crops. Nor does it preclude or depend upon an uncertain social acceptance of large-scale dietary changes. Rather, Nitrogen2.0 focuses on transformational changes that could be achieved within the next few decades with appropriate R&D investments to substantially improve targeted efficiencies and circularities. Research initiatives on improving animal feed management, crop breeding, and manureshed management are already underway, but they need to be accelerated and linked in a systems approach in order to achieve the transformational potential of Nitrogen2.0. It will require collaboration across disciplines, as exemplified by the participation of the Banbury workshop experts who are launching this vision. Nitrogen2.0 is compatible with other efforts to advance regenerative agriculture or to encourage more plant-based diets, but it focuses primarily on targeted efficiencies and circularity of N use. Achieving the full potential of the Nitrogen2.0 vision may require decades of R&D and scaling-up, but it is grounded in strong existing science and practical experience that can form the basis for action now.
(funded by the Cold Spring Harbor Laboratory Corporate Sponsor Program)
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