The research examines a trade relationship dominated by U.S. exports of soybeans, maize and other crops used to feed livestock in China. Under the alternative scenario, meat, milk and eggs would be produced in the United States and exported to China instead of shipping large quantities of feed across the Pacific. The researchers estimate that this shift could reduce global agricultural nitrogen loss by 38%, lower greenhouse gas emissions by 17% and cut environmental damage costs by 32% compared with the current feed-based trading system. U.S. agricultural trade revenue could rise by approximately US$10.5 billion, with an uncertainty range of ± US$2.4 billion.

The findings, published in Nitrogen Cycling, are based on comparisons of three trade scenarios using data from 2022. The first represented highly restricted agricultural trade between the United States and China. The second reflected the current system, in which the United States primarily exports feed crops to support livestock production in China. The third modeled a food-trade system in which livestock production would be expanded in the United States and animal-derived products would be exported to China.

The current feed trade already offers some environmental advantages over producing the same crops entirely in China. The study estimates that existing U.S.-China feed trade reduces global nitrogen loss by about 32% and greenhouse gas emissions by roughly 7%. One reason is that U.S. agriculture generally uses nitrogen more efficiently. Nitrogen fertilizer is essential for high crop yields, but nitrogen that is not absorbed by plants can escape into soil, rivers and the atmosphere, where it contributes to water pollution, algal blooms, air pollution and climate change.

However, shipping feed across the Pacific also creates a major nutrient-recycling gap. Soybeans and maize are grown largely in the United States, while the animals that consume them are raised mainly in China. More than 40% of the nitrogen contained in imported feed is eventually lost as manure in China, according to the researchers. Instead of being returned to the cropland that produced the feed, this nitrogen is often concentrated near livestock facilities, where storage and disposal can become difficult. The result is a fragmented nutrient cycle in which one country produces the feed and another manages most of the waste.

Producing livestock closer to the crops that supply their feed could help reconnect those parts of the agricultural system. In the food-trade scenario, the researchers found that less feed nitrogen would be needed to produce the same amount of meat, milk and eggs because livestock production in the United States was estimated to be more efficient in the modeled system. As a result, greenhouse gas emissions associated with the trade relationship could fall from approximately 57 ± 8 million metric tons of carbon dioxide equivalent to 48 ± 7 million metric tons.

The potential benefits would not be distributed evenly across the United States. Expanding livestock production could increase nitrogen losses and greenhouse gas emissions in several major agricultural regions, including parts of Iowa, North Carolina, California, Texas and the Great Plains. More animals would mean greater amounts of manure, and without adequate storage, treatment and application systems, local pollution could intensify even while global emissions declined. The result highlights a central challenge of climate-smart agriculture: a policy that improves global averages can still create serious environmental pressures in particular communities.

To address that risk, the researchers also examined strategies for improving nutrient management. Recycling plant-based food waste as animal feed could reduce the demand for newly grown feed crops, while better manure recovery could capture nitrogen and return it to agricultural soils as fertilizer. Combining these approaches with a shift toward animal-product exports could substantially reduce the additional environmental burden created by increased U.S. livestock production. In technical terms, the strategy aims to close nutrient loops, reduce nitrogen leakage and make more efficient use of nutrients already present in the food system.

The authors stress that their results do not mean the United States should simply expand livestock production or replace all feed exports with meat and dairy exports. The study instead presents trade composition as an overlooked environmental policy tool. Decisions about agricultural commerce are typically guided by market prices, geopolitical concerns and food availability, but the environmental consequences depend heavily on where crops are grown, where animals are raised and where nutrients end up after harvest. “The environmental impact of agricultural trade depends not only on how much countries trade, but also on what they trade and where production takes place,” said corresponding author Xin Zhang.

The study suggests that future trade agreements could be evaluated using a broader set of indicators, including nitrogen loss, greenhouse gas emissions, manure-management capacity, water pollution and economic returns. A carefully designed portfolio of feed and food trade, supported by food-waste recycling and improved manure recovery, could make international agriculture more resource-efficient. As the global demand for animal products continues to grow, the research offers a provocative message: changing the direction and form of food trade may be almost as important as increasing production efficiency on individual farms.

Subject of Research: Agricultural trade, nitrogen cycling, livestock production, nutrient recycling and greenhouse gas emissions

Article Title: Shifting U.S.−China trade from feed to food reduces global agricultural nitrogen loss and greenhouse gas emissions

News Publication Date: 27 July 2026

Web References: https://doi.org/10.48130/nc-0026-0011

References: Wang Y, Gu B, Zhang X. 2026. “Shifting U.S.−China trade from feed to food reduces global agricultural nitrogen loss and greenhouse gas emissions.” Nitrogen Cycling 2: e024. DOI: 10.48130/nc-0026-0011

Image Credits: Yanyu Wang, Baojing Gu and Xin Zhang

Keywords

U.S.-China agricultural trade, animal feed, animal-derived foods, nitrogen loss, nitrogen cycle, greenhouse gas emissions, livestock production, manure management, food-waste recycling, sustainable agriculture, agricultural emissions, environmental economics

Nitrogen, a vital nutrient for crop growth, predominantly enters agricultural soils through synthetic fertilizers and organic amendments such as manure. However, the excessive application or inefficient recycling of nitrogen contributes significantly to environmental degradation, including groundwater contamination, greenhouse gas emissions, and air quality deterioration through ammonia volatilization. Recognizing manure as a critical reservoir of nitrogen, yet underutilized in many farming systems, the research foregrounds its role not merely as waste but as a valuable resource for sustainable nutrient management.

At the core of this study is a modeling framework meticulously calibrated to capture the nitrogen inputs, transformations, losses, and eventual recycling potential within manure management systems across varying geographical and operational contexts. The framework integrates diverse datasets encompassing livestock population statistics, manure production rates, nitrogen excretion coefficients, and manure handling practices. Such integration facilitates estimation of nitrogen balance at multiple scales—from farm level to national aggregates—illuminating discrepancies and inefficiencies in current manure nutrient management.

Importantly, the analysis does not remain static but anticipates evolving conditions by incorporating future scenarios reflective of projected changes in livestock production, technological advancements, regulatory landscapes, and climatic influences. By doing so, the study imbues prognostic value, outlining potential trajectories of manure nitrogen utilization if current trends persist or if targeted interventions are implemented. This forward-looking perspective equips policymakers, farmers, and stakeholders with foresight critical to achieving circular agricultural nutrient systems.

One pivotal revelation from the research is the significant nitrogen surplus generated by livestock manure relative to crop nitrogen demand within certain US regions, notably where intensive animal farming prevails. This surplus often leads to nitrogen accumulation in soils and adjoining ecosystems, exacerbating environmental and human health risks. The framework delineates these hotspots and quantifies excess nitrogen, thus identifying priority zones for targeted manure recycling improvements.

Furthermore, the study elucidates how current manure handling and land application techniques influence nitrogen partitioning, loss pathways, and ultimately recycling efficiency. For example, it highlights that practices such as surface spreading without incorporation into soil can lead to substantial ammonia emissions and nitrogen volatilization, reducing the nitrogen available for crop uptake. Conversely, technologies like solid-liquid separation, anaerobic digestion, and injection methods have the potential to enhance nitrogen retention and recycling efficacy.

Another dimension explored is the interaction between manure nutrient management and emerging energy systems. Anaerobic digestion technology, which converts manure into biogas, simultaneously produces a nutrient-rich digestate. The utilization of this digestate as a fertilizer substitute presents a promising avenue for nitrogen recycling while contributing to renewable energy development. The framework evaluates this multifunctional potential, emphasizing policy alignment and infrastructure development as catalysts for adoption.

The research also consciously addresses the socio-economic and logistical barriers impeding widespread manure recycling. Transport costs, nutrient balance mismatches between livestock density and cropland availability, and regulatory heterogeneity constrain efficient manure redistribution. The framework quantifies these limitations, suggesting that overcoming them necessitates coordinated regional nutrient management strategies, financial incentives, and infrastructure investments.

Moreover, the authors underscore the critical role of enhanced data collection and monitoring systems to refine nitrogen balance estimations and validate model predictions. Emerging technologies such as remote sensing, precision agriculture, and digital tracking of manure flows can revolutionize data granularity and temporal resolution, facilitating adaptive management and policy responsiveness.

The study’s implications stretch beyond environmental stewardship into the realm of food security and climate change mitigation. Optimizing manure nitrogen recycling can reduce dependence on synthetic fertilizers, whose production is energy-intensive and carbon-emitting, thereby lowering the carbon footprint of agricultural systems. At the same time, it enhances soil fertility and crop yields, supporting resilient food production amidst growing global demand.

Collaboration between researchers, industry stakeholders, and government agencies emerges as a recurring theme essential to translating the framework’s insights into practice. By fostering knowledge exchange, technology adoption, and coordinated policy frameworks, the ambitious goal of closing nitrogen loops in agriculture becomes increasingly attainable.

Finally, this trailblazing work serves as a blueprint adaptable to other countries facing analogous manure nutrient challenges. Its methodological rigor, combined with scenario-based foresight, presents a scalable model for global efforts to harmonize livestock production with sustainable nutrient cycling, thereby advancing the planetary boundaries of agricultural sustainability.

In summary, this innovative framework represents a landmark advance in sustainable agricultural nutrient management. By providing a transparent, integrative, and predictive tool for manure nitrogen balance and recycling potential, it empowers stakeholders to identify inefficiencies, implement best practices, and ultimately transform manure from an environmental liability into a cornerstone of circular agriculture.

Subject of Research: Estimation of manure nitrogen balance and recycling potential within the United States under current and projected future conditions.

Article Title: A framework for estimating manure nitrogen balance and recycling potential for current and future conditions in the USA.

Article References:
Wang, Y., Zhang, X., Spiegal, S. et al. A framework for estimating manure nitrogen balance and recycling potential for current and future conditions in the USA. Nat Food (2026). https://doi.org/10.1038/s43016-026-01312-5

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s43016-026-01312-5

Published in the journal Nitrogen Cycling, the research delineates a comprehensive field investigation conducted near a large-scale pig farm located in central China. Scientists meticulously measured soil N2O emissions across various sites positioned 50 to 500 meters downwind of the farm, where a natural gradient of ammonia deposition was present. The findings reveal a compelling trend: soils subjected to higher atmospheric ammonia loads exhibited a marked increase in nitrous oxide emissions, providing direct evidence of ammonia’s indirect yet significant influence on climate-relevant greenhouse gases.

Livestock farming stands as the preeminent global source of ammonia emissions, which primarily escape into the atmosphere from animal enclosures and manure storage systems. Once airborne, ammonia molecules travel and deposit onto adjacent soils and ecosystems, initiating a cascade of biochemical transformations. While ammonia itself is not a greenhouse gas, its transformation upon deposition activates complex nitrogen cycling pathways mediated by soil microorganisms, which in turn amplify N2O production — a potent greenhouse gas with a global warming potential nearly 300 times that of carbon dioxide over a hundred-year horizon.

To elucidate the mechanisms underpinning this interaction, the team focused on key soil microbial communities responsible for nitrogen transformations. They identified an increased abundance of ammonia-oxidizing archaea (AOA), microorganisms that catalyze the conversion of ammonium (NH4+) to nitrate (NO3−) through nitrification. This microbial process, stimulated by elevated ammonia deposition, was linked to heightened nitrous oxide production as a byproduct. These insights were further verified by controlled laboratory experiments demonstrating significantly greater N2O emissions from soils treated with ammonium-based nitrogen sources compared to nitrate additions.

This microbial pathway is critical because nitrification processes inherently involve intermediate transformations where nitrous oxide is produced. As ammonia accumulates due to deposition from livestock emissions, it serves as an abundant substrate fueling AOA activity and thus driving an increase in N2O emission rates from soil. This discovery underscores the intricate yet impactful ways in which agricultural ammonia can exacerbate climate forcing gases beyond its immediate air quality implications.

Quantitative estimates from the study suggest that within the 500-meter radius surrounding the pig farm, nitrous oxide emissions from soil could reach approximately 69.7 kilograms of nitrogen per year. This corresponds to about 1.3 percent of the total ammonia nitrogen deposited — a figure exceeding the emission factor commonly adopted in international climate models. Such discrepancies highlight the necessity for revising current greenhouse gas inventories to incorporate ammonia-driven nitrous oxide emissions more accurately, particularly in regions with intensive livestock production.

The ramifications of this research extend beyond simply identifying a new source of greenhouse gases. They point to a critical feedback loop where livestock ammonia emissions enhance soil nitrification and denitrification processes, escalating N2O emissions that counteract the climate benefits of methane mitigation efforts typically targeted in the agricultural sector. This nuanced understanding compels a holistic approach to managing nitrogen emissions from farming practices to achieve meaningful climate impact reductions.

Moreover, nitrous oxide’s dual environmental threat is significant — besides its greenhouse warming capacity, it is recognized today as the principal anthropogenic ozone-depleting substance. Its prolonged atmospheric lifetime and potent effects on the stratospheric ozone layer exacerbate threats to human health and ecosystems, underscoring the urgency of mitigating all major N2O sources, including those previously underappreciated like ammonia deposition zones near livestock operations.

What makes this study particularly timely is the global trend of expanding livestock production driven by increasing demand for animal protein. As farming intensifies, ammonia emissions are likely to rise correspondingly, amplifying the risk of enhanced N2O emissions through the mechanism this study has elucidated. This emerging knowledge base calls for integrating ammonia reduction strategies alongside methane and nitrous oxide control measures within sustainable agricultural policy frameworks.

The authors advocate for targeted mitigation techniques, emphasizing that reducing ammonia volatilization from animal housing, manure management, and field application could serve dual purposes by improving air quality and substantially decreasing nitrous oxide emissions. Adopting such integrative approaches would help align agricultural practices with global climate objectives, closing a critical gap in greenhouse gas mitigation efforts that has escaped attention until now.

Jianlin Shen, the study’s corresponding author, highlighted the novelty and importance of these findings: “Our work reveals a significant, yet often overlooked, climatic consequence of ammonia pollution from livestock farms. By enhancing soil nitrification and associated nitrous oxide emissions, ammonia creates a secondary greenhouse gas source that must be addressed if we hope to curb agricultural impacts on climate change effectively.”

This innovative research not only deepens the understanding of nitrogen cycling in relation to anthropogenic activities but also sets the stage for revising emission models and environmental regulations worldwide. Ongoing and future studies are expected to broaden this work’s geographical scope and refine emission factors across diverse agroecosystems, ultimately contributing to more precise climate risk assessments and mitigation planning.

In sum, the intricate interplay between atmospheric ammonia from livestock and soil microbial activity driving nitrous oxide emissions reveals a hidden dimension of agricultural environmental impact. Recognizing and mitigating this link represents a crucial step forward in addressing both climate change and ozone depletion, further stressing the interconnectedness of ecosystem processes in shaping global environmental futures.

Subject of Research:
Not applicable

Article Title:
Increased soil N2O emissions under natural gradient of atmospheric NH3 deposition

News Publication Date:
28-Jan-2026

Web References:
https://doi.org/10.48130/nc-0025-0023

References:
Yi W, Liu G, Kang M, Wang J, Yuan H, et al. 2026. Increased soil N2O emissions under natural gradient of atmospheric NH3 deposition. Nitrogen Cycling 2: e011. DOI: 10.48130/nc-0025-0023

Image Credits:
Wuying Yi, Guoping Liu, Man Kang, Juan Wang, Hongzhao Yuan, Deli Chen, Jinshui Wu & Jianlin Shen

Keywords:
Emission detectors, Greenhouse gases, Animals

At the core of this investigation lies the agroecosystem model ecosys, a powerful tool designed to simulate complex ecological interactions within agricultural landscapes. By integrating long-term field data and state-of-the-art modeling techniques, researchers explored why corn following soybeans invariably exhibits superior yield compared to continuous corn cultivation, especially under standard nitrogen fertilization regimens. The model elucidates how the decomposition characteristics of soybean residues accelerate soil warming in early spring, thereby stimulating microbial activity and enhancing nitrogen mineralization from soil organic matter. This liberation of plant-available nitrogen mimics the benefits of starter fertilizers and underpins the observed increase in corn biomass and grain yield.

Yet, the relationship between nitrogen fertilization and yield enhancement through rotation is anything but straightforward. The study demonstrates that the yield advantage diminishes as nitrogen inputs rise, essentially tapering off at high fertilization levels. This nuanced finding underscores the importance of calibrating fertilizer applications to optimize the synergistic benefits of crop rotation without incurring diminishing returns or unnecessary environmental burdens. It also confronts the widespread assumption that more fertilizer invariably leads to better yields, emphasizing precision nutrient management grounded in ecological understanding.

The environmental dimension of the corn-soybean rotation reveals a complex tapestry of benefits and trade-offs. On one hand, rotation significantly reduces the emissions of potent greenhouse gases such as nitrous oxide and ammonia from soils, contributing to improved air quality and climate resilience. On the other hand, this benefit is counterbalanced by a decline in soil organic carbon stocks, primarily driven by the rapid decomposition of soybean residues compared to continuous corn. Lower soil organic matter levels can impair soil structure, water retention, and long-term fertility, presenting a paradox where short-term gains in productivity and reduced emissions potentially sow the seeds of longer-term soil degradation.

Nitrogen leaching patterns further complicate the environmental narrative. While leaching diminishes during soybean years due to the absence of fertilizer inputs, it paradoxically increases in the following corn year. This phenomenon is attributed to the mineralization of organic nitrogen released from decomposed soybean residues, elevating the risk of nutrient loss to groundwater systems. Such dynamics highlight the delicate balance between nutrient recycling and environmental protection, emphasizing that rotation-induced benefits must be managed carefully to mitigate unintended consequences.

Economically, the analysis provides compelling evidence favoring corn-soybean rotation, especially when nitrogen fertilizer rates are judiciously maintained at lower levels. The economic model, leveraging historical commodity prices, indicates that rotation can enhance net returns by up to $458 per acre compared to continuous corn production. This financial advantage is particularly pronounced under market conditions featuring higher soybean prices relative to corn and moderate fertilizer costs. However, this profitability edge narrows or even reverses when corn prices spike or nitrogen inputs surge, revealing the sensitivity of economic outcomes to volatile market forces and input cost fluctuations.

Crucially, the study emphasizes that profitability is not dictated solely by corn yield improvements or fertilizer consumption but is intricately linked to the performance and market valuations of both crops in the rotation. This holistic economic perspective encourages tailored management strategies that reflect not only biological but also financial realities faced by farmers. As commodity markets continue to fluctuate and environmental regulations tighten, such integrated approaches will be essential in guiding adaptive and resilient farming systems.

This research challenges the agronomic community to move beyond traditional one-dimensional assessments of cropping systems toward multifactorial evaluations that consider long-term soil health, environmental footprints, and economic sustainability simultaneously. Nitrogen management emerges as a fulcrum around which these competing objectives must be balanced. By fine-tuning fertilizer application rates to harness the natural nitrogen contributions provided by soybean residues, farmers can reduce input costs, limit greenhouse gas emissions, and sustain yields, while also guarding against soil organic matter depletion and nutrient leaching.

The findings also underscore the importance of temporal scales in understanding agroecosystem dynamics. Organic matter changes, often overlooked in short-term experiments, accumulate over years and decades, profoundly influencing nitrogen availability and soil function. This calls for long-term monitoring and modeling efforts to capture the cumulative impacts of cropping choices and fertilization regimes. The study’s coupling of empirical data with advanced ecosystem modeling provides a robust template for such endeavors, demonstrating the power of interdisciplinary approaches in agricultural science.

Moreover, the research highlights the intricate feedback loops between plant residue decomposition, soil microbial processes, and nutrient cycling. Soybean residues decompose more rapidly than corn residues due to their biochemical composition, which in turn accelerates nitrogen mineralization and alters carbon turnover rates. These microbial-mediated processes translate into tangible effects on crop growth and environmental emissions, illustrating the centrality of soil biology in mediating agroecosystem functions. By advancing the understanding of these microbial and biochemical interactions, the study opens pathways for designing management practices that exploit natural ecological processes to improve sustainability.

While the economic analysis presents crop rotation as generally advantageous under specific fertilization and market scenarios, it also flags the absence of a universal prescription applicable to all farmers and agroecosystems. The trade-offs between environmental stewardship, economic returns, and agronomic performance demand flexible strategies customized to local soil types, climate conditions, and farmer goals. Policymakers and extension services can leverage these insights to develop nuanced recommendations and incentives that promote best practices tailored to diverse agricultural landscapes.

Ultimately, this comprehensive investigation documented in the paper titled “Comparing continuous-corn and soybean-corn rotation cropping systems in the U.S. central Midwest: Trade-offs among crop yield, nutrient losses, and change in soil organic carbon,” published in Agriculture, Ecosystems & Environment, represents a pivotal advance in agroecosystem research. Supported by major funding bodies including the National Science Foundation, NASA, and the U.S. Department of Energy, it offers an authoritative scientific basis for the continued promotion of crop rotations. By integrating agronomic performance, environmental impacts, and economic analyses, the study equips farmers, researchers, and policymakers with actionable knowledge to navigate the complexities of modern agriculture and to enhance the sustainability and profitability of U.S. Midwest cropping systems for generations to come.

Subject of Research: Impacts of corn-soybean rotation on crop yield, environmental emissions, soil organic carbon, and economic returns in the U.S. Midwest.

Article Title: Comparing continuous-corn and soybean-corn rotation cropping systems in the U.S. central Midwest: Trade-offs among crop yield, nutrient losses, and change in soil organic carbon

Web References:
https://doi.org/10.1016/j.agee.2025.109739

Image Credits: Ziyi Li, University of Illinois Urbana-Champaign

Keywords: corn-soybean rotation, crop yield, nitrogen mineralization, soil organic carbon, nitrogen leaching, nitrous oxide emissions, agroecosystem model, ecosystem sustainability, economic returns, Midwest agriculture, nutrient cycling, crop residue decomposition