Global impacts of reactive nitrogen

Effects of human activities on nitrogen flow in the rural area of the Taihu watershed in China

Feature Presentation, Global impacts of reactive nitrogen, Impact Presentation

YanhuaWang^a,c,d, ZucongCai^a,c,d, Xiaoyuan Yan^b, HaoYang^a,c,d

^aSchool of Geography Science, Nanjing Normal University, 1 Wenyuan Road, Qixia, Nanjing 210023, China;

^bInstitute of Soil Science, Chinese Academy ofSciences, Nanjing 210008, China;

^cJiangsu Provincial Key Laboratory of Materials Cycling and Pollution Control, Nanjing, China;

^dJiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing, China

Abstract

Nitrogen limits primary productivity in ecosystems. To overcome this limitation and maintain food security, densely populated agricultural regions in developing nations now use synthetic nitrogen fertilizers to boost yields. However, nitrogen saturation of aquatic ecosystems was observed here and there, i.e. Taihu Lake, Dianchi Lake and lots of rivers in the watershed. Human activities have more than doubled the annual amount of reactive nitrogen (Nr) entering terrestrial ecosystems since the preindustrial era (Galloway 1998; Green et al 2004). Increased gradually Nr emitted to the atmosphere resulting in the haze, greenhouse effects, acid rain and so on. In this study, we assessed the fate of Nr in the rural area of the Taihu watershed, China. A detailed quantification of Crop Production-Livestock Breeding System (CLS) was constructed in this study. Material flow analysis method and the principle of conservation of mass were used.

Nitrogen balance and use efficiency in the Calapooia River Watershed, Oregon, United States

Feature Presentation, Global impacts of reactive nitrogen, Impact Presentation

Jiajia Lin¹, Jana Compton², George Mueller-Warrant³, William Matthews⁴, Scott Leibowitz⁵

¹National Research Council, based at US Environmental Protection Agency, Western Ecology Division, 200 SW 35th St, Corvallis, OR 97333, Lin.jiajia@epa.gov

²US Environmental Protection Agency, Western Ecology Division, 200 SW 35th St, Corvallis, OR 97333, Compton.Jana@epa.gov

³US Department of Agriculture, Agricultural Research Service, 3420 NW Orchard Ave, Corvallis, OR 97331, George.Mueller-Warrant@ars.usda.gov

⁴Oregon Department of Agriculture, Natural Resources Division, 635 Capitol St NE, Salem, OR 97301, Wmatthews@oda.state.or.us

⁵US Environmental Protection Agency, Western Ecology Division, 200 SW 35th St, Corvallis, OR 97333, Leibowitz.Scott@epa.gov

Abstract

Reducing nitrogen (N) released into the environment through greater N use efficiencies (NUE) is a current challenge in watershed management. Examining N sources and sinks at local scales allows for better watershed-scale N use. We use data on land-use, CAFOs, N deposition, stream chemistry, and crop-level and county-level fertilizer use to assess the N inputs, exports and retention in the Calapooia River Watershed (CRW). The CRW is influenced by intensive agricultural activities, mostly in grass seed crops. Our results demonstrate that fertilizer is the dominant N input on agricultural land, with an average rate of 130 kg N/ha/yr on these subwatersheds. Deposition and alder fixation are the two main sources of N on forested land, with an average rate of <10 kg N/ha/yr. About 50-60% of the annual hydrologic N yield occurs during wet winter and reaches 40 kg N/ha per season. Summer TN yield is minimum, as low as <1 kg N/ha per season. At the CRW scale, annual stream export is 19% of the total N inputs. On average, about 41% of total N input is removed annually via crop harvest among the 58 subwatershed. The proportion of net N input that is “retained” in Calapooia is within the same range of estimates of northeastern watersheds. Our analysis also shows that runoff alone explains 62% of the variance in fractional N export in the U.S. watersheds.

Determining nitrogen removal in US sewage treatment

Feature Presentation, Global impacts of reactive nitrogen, Impact Presentation

Lia R. Cattaneo¹, Robert Bastian², Lisa M. Colosi¹, Allison M. Leach³, James N. Galloway¹

¹University of Virginia, 291 McCormick Road, Charlottesville, VA, 22904 USA, lrc4yd@virginia.edu

²United States Environmental Protection Agency, 1200 Pennsylvania Ave., NW, Washington, D.C. 20460

³University of New Hampshire, 131 Main Street, 107 Nesmith Hall, Durham, NH, 03824 USA

Abstract

Most of the nitrogen (N) in food passes through the human body, is excreted, and enters the wastewater stream. This sewage N is an important component of the food consumption N footprint. The US N-Calculator (a per capita nitrogen footprint tool) calculates N removal from sewage by estimating the proportion of homes connected to wastewater treatment plants (WWTPs) with tertiary treatment N removal technologies. However, this assumes that no N is removed in WWTPs with primary or secondary treatment or in WWTPs with tertiary treatment processes other than nitrogen removal. This paper uses a mass balance approach to revise the factor used in the US N-Calculator to better represent the N removal from sewage treatment in the US. N in wastewater can have several fates: release to the environment through septic systems, release to the environment through WWTPs, release to the environment in disposed sludge, conversion to N₂ in WWTPs, and beneficial use as land-applied sludge. The national average N removal factor (55%) represents N converted to N₂ or used as beneficial sludge compared with the N in wastewater. The removal from just WWTPs was 73%. The new total removal reduces the average US per capita food consumption N footprint by 2.63 kg N, resulting in a total footprint decrease of 6.7%.

Evaluation of historical global gaseous nitrogen emissions from croplands considering NH4+ and NO3- forming fertilizer species in global fertilizer dataset

Feature Presentation, Global impacts of reactive nitrogen, Impact Presentation

Kazuya NISHINA, Akihiko ITO, Seiji HAYASHI

¹National Institute for Environmental Studies 16-2, Onogawa, Tsukuba, 305-8506, JAPAN, https://www.nies.go.jp/chiiki/en/index_en.html, nishina.kazuya@nies.go.jp

Abstract

We developed a new historical global N fertilizer map (half degree resolution) during 1961-2010 based on FAOSTAT and various global dataset. This new map incorporated the fraction of NH₄⁺ (and NO₃^–) into N fertilizer inputs by utilizing fertilizer species information in FAOSTAT. In the data processing, we applied a statistical data imputation method for the missing data in FAOSTAT. The multiple imputation method enabled to fill gaps of the time-series data by the plausible values. In this study, we evaluated NH₃, NO, and N₂O emissions from agricultural soils with biogeochemical model “VISIT” using the developed map. During 1961-2010, synthetic fertilizer consumption increased from 15 Tg-N to 110 Tg-N at global. In this period, the global average fraction of NH₄⁺ was about 80% to synthetic N fertilizer consumption. The most countries showed NH₄⁺ based fertilizer are dominant, however, the ratio NH₄⁺:NO₃^– in N fertilizer inputs shows clear differences among countries and periods. Considering the ratio NH₄⁺:NO₃^– in N fertilizer inputs, the simulated NH₃ volatilization were generally reduced, compared to N fertilizer input dealt as only NH₄⁺input assumption. On the other hand, NO and N₂O emissions shows both positive and negative impacts using the NH₄⁺:NO₃^– fertilizer map. Our new map can be utilized and bring new insights in the global model studies for the assessment of historical terrestrial N cycling changes.

The unexpectedly large nitrogen footprint of Australians

2016 INI, Feature Presentation, Global impacts of reactive nitrogen

Xia Liang¹, Allison M. Leach², James N. Galloway³, Baojing Gu^4,5, Shu Kee Lam¹, Deli Chen¹

¹Crop and Soil Science Section, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Victoria 3010, Australia. E-mail: xial1@student.unimelb.edu.au

²Department of Natural Resources & Earth Systems Science and The Sustainability Institute, University of New Hampshire, 107 Nesmith Hall, 131 Main Street, Durham, NH, 03824, USA.

³Department of Environmental Sciences, University of Virginia, Clark Hall, 291 McCormick Road, P.O. Box 400123, Charlottesville, VA 22904-4123, USA

⁴Department of Land Management, Zhejiang University, Hangzhou 310058, PR China

⁵Policy Simulation Laboratory, Zhejiang University, Hangzhou 310058, PR China

Abstract

Anthropogenic release of reactive nitrogen (Nr; all species of N except N₂) to the global nitrogen (N) cycle is substantial and it negatively affects human and ecosystem health. A novel metric, the N footprint, provides a consumer-based perspective for N use efficiency and connects lifestyle choices with N losses. Here we report the first full-scale assessment of the anthropogenic Nr loss by Australians. Despite its ‘clean and green’ image, Australia has the largest N footprint (47 kg N cap^-1 yr^-1) both in food and energy sectors among all countries that have used the N-Calculator model. About 69% of the Australia’s N footprint is attributed to food production and consumption, with the rest from energy consumption. Beef consumption and production is the major contributor of the high food N footprint, while the heavy dependence on coal for electricity explains the large energy N footprint. Our study demonstrates opportunities for managing N loss and lifestyle choices to reduce the N footprint.

Quantification of the German nitrogen cycle

2016 INI, Feature Presentation, Global impacts of reactive nitrogen

Markus Geupel¹, Jakob Frommer²

¹German Environment Agency, Wörlitzer Platz 1, Dessau, Germany, 06846, www.umweltbundesamt.de, markus.geupel@uba.de

² Stadt Würzburg, Fachbereich Umwelt- und Klimaschutz, Karmelitenstr. 20, 97070 Würzburg, jakob.frommer@stadt.wuerzburg.de

Abstract

Nitrogen and its compounds behave very differently in the environment. While atmospheric nitrogen is practically inert, the oxidised and reduced compounds are reactive. Human activity has led to massive changes to the natural nitrogen cycle over the past century and a drastic increase has been seen in the amounts of reactive nitrogen in the environment. Also in Germany the excessive release of reactive nitrogen compounds into the environment leads to a series of problems which must be urgently addressed. These include the loss of aquatic and terrestrial biodiversity, the impairment of air quality, the increased release of greenhouse gases, and constraints on the use of groundwater as drinking water. To improve knowledge on reasons for this situation we reviewed literature and databases to quantify the German nitrogen cycle. In Germany, some 4.2 million tonnes of reactive nitrogen enter into the nitrogen cycle annually, corresponding to some 50 kg per person. While considerable reductions have been achieved in oxidised nitrogen emissions from fossil fuel burning and also from wastewater management, reductions in the agricultural sector have been much less successful. The failure to meet targets is due in part to the fact that a comprehensive solution to the problems posed by nitrogen is hardly possible by implementing separate technical measures in individual areas. Therefore, it is necessary to adopt an integrated approach to the various problems in all relevant policy areas.

Can Nitrogen Management maintain Grain Protein Content of wheat under elevated CO2? A FACE study

Feature Presentation, Global impacts of reactive nitrogen

Cassandra Walker, Roger Armstrong, Joe Panozzo, Glenn Fitzgerald

Department of Economic Development, Jobs, Transport and Resources, Horsham, Victoria, 3400, cassandra.walker@ecodev.vic.gov.au

Abstract

The impact of different nitrogen (N) management strategies (rate, split-N application, foliar-N application, legume pre-cropping) were assessed for their effectiveness in reversing the reduction of grain protein content in order to maintain grain quality of wheat (cv. Yitpi) under elevated CO₂ (eCO₂) using Free Air Carbon Dioxide Enrichment (FACE).

Preliminary results show that under eCO₂ conditions the plant biomass, grain yield and grain size increased and that grain protein content decreased when no N fertiliser was applied (N0). Significant grain yield responses to increasing rates of N fertiliser (applied at sowing) were observed in Yitpi, with the grain yield under eCO₂ conditions increasing by 63% when 100 kg N/ha (N100) was applied compared with N0; an increased response (59%) was also observed under ambient CO₂ conditions. The largest grain yield response for a N management strategy compared with N0 under eCO₂ conditions was when Yitpi was grown after prior rotation with annual medic pasture (M), with an increase of 74%. Grain protein increased significantly (31%) under eCO₂ conditions at N100 compared with N0, however it seems that vegetative growth demand ‘took preference’ with an increase in dry matter (DC90) of 101% under eCO₂ conditions at N100 compared with N0. Under ambient CO₂ only 50 kg N/ha at sowing was required to gain a similar increase in grain protein content. When comparing the grain protein content of Yitpi sown into medic stubble (M) to that at N0, there was a significant increase (P = 0.05) at ambient CO₂ conditions, however, under eCO₂ conditions no significant response observed.

Solution scenarios and the effect of top down versus bottom up N mitigation measures – Experiences from the Danish Nitrogen Assessment

Feature Presentation, Global impacts of reactive nitrogen

Tommy Dalgaard¹, Steen Brock², Christen D. Børgesen¹, Morten Graversgaard¹, Birgitte Hansen³, Berit Hasler⁴, Ole Hertel⁴, Nicholas John Hutchings¹, Brian Jacobsen⁵, Lars Stoumann Jensen⁶, Chris Kjeldsen¹, Jørgen E Olesen¹, Jan K Schjørring⁶, Torben Sigsgaard⁷, Peter Stubkjær Andersen⁸, Mette Termansen⁴, Henrik Vejre⁸, Mette Vestergaard Odgaard¹, Wim de Vries⁹, and Irene A Wiborg¹⁰

¹Department of Agroecology, Aarhus University, Blichers Allé 20, DK-8830 Tjele, Denmark. tommy.dalgaard@agro.au.dk

² Aarhus University, Dept. of Culture and Society. Jens Chr. Skous Vej 7, DK-8000 Aarhus C, Denmark.

³Geological Survey of Denmark & Greenland – GEUS. Lyseng Allé 1, DK-8270 Højbjerg, Denmark.

⁴Aarhus University, Dept. of Environmental Sciences, Frederiksborgvej 399, DK-4000 Roskilde, Denmark.

⁵University of Copenhagen, Dept. of Food and Resource Economics. Rolighedsvej 25, DK-1870 Frederiksberg C, Denmark.

⁶University of Copenhagen, Dept. of Plant and Environmental Sciences. Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark.

⁷Aarhus University, Dept. of Public Health, Bartholin Allé 2, 8000 Aarhus C, Denmark.

⁸University of Copenhagen, Dept. Geosciences and Natural Resource Management. Rolighedsvej 23, DK-1858 Frb. C, Denmark.

⁹Wageningen University, Alterra. Droevendaalsesteeg 4, 6708PB Wageningen, The Netherlands.

¹⁰SEGES, Knowledge Centre for Agriculture. Agro Food Park 20, DK-8200 Aarhus N, Denmark.

Abstract

This paper presents methods and preliminary results developed within The Danish Nitrogen Research Alliance (www.dNmark.org). This include solution scenarios to meet the N loss reduction goals set by the EU Water Framework Directive, The National Emissions Ceilings Directive, and the paradigm shifting, new 2016 Danish N action plan. Compared to the previous series of action plans 1985-2016, the new action plan shifts from input to output based regulation introduces geographically targeted measures on top of the existing general regulation, with more room for green growth via an intensified use of N and increased economic benefits from production as long as the defined environmental targets are met. We argue that this opens up for new bottom up methods to be developed for locally adapted solutions to the N pollution reduction challenge, top down measures to further increase N use efficiency.

Minimising the land area used by agriculture without petrochemical nitrogen

Feature Presentation, Global impacts of reactive nitrogen

Rowan Eisner, Leonie Seabrook, Clive McAlpine

University of Queensland, Brisbane, Queensland 2067, www.gpem.uq.edu.au/lec, r.eisner@uq.edu.au

Abstract

Biodiversity is threatened in a post-carbon future due to the expansion of agriculture resulting from reduction in the use of petrochemical-based fertilisers. Here we prioritise alternative fertilisers based on their potential to minimise future agricultural expansion. We map the threat to biodiversity globally for the best-case scenario for replacing mineral N. To consider both biofixation and industrial nitrogen fixation, we calculated the footprint for three green manures (azolla, algae and alfalfa), and three options for mineral nitrogen production using renewable energy to power the Haber-Bosch process (wind, photovoltaics and thermal solar). Solar-powered Haber-Bosch would provide the minimum global footprint, with concentrated thermal solar power stations a particularly attractive option since they are best situated in low-rainfall areas where biodiversity is also lower. This approach would also save about 1% of global carbon emissions from the combustion of fossil fuels. Mapping the biodiversity impact of expanding the current solar power station footprint to meet the area required to replace the fossil fuel powered mineral N shows a reduction in biodiversity impact from footprint expansion to less than one ten-thousandth of that which would occur with current management practices in the absence of mineral N. A proactive approach is required in selecting alternatives to mineral N in order to limit the impact of agriculture’s post-carbon footprint on biodiversity.

Turning points of global anthropogenic nitrogen creation and their climate effect

Feature Presentation, Global impacts of reactive nitrogen

Baojing Gu^1,2,*, Xiaotang Ju³_,Yiyun Wu², Jan Willem Erisman^4,5, Albert Bleeker⁶, Stefan Reis^7,8, Mark A. Sutton⁷, Shu Kee Lam⁹, Oene Oenema¹⁰, Rognvald Smith⁷, Deli Chen⁹, Xinyue Ye¹¹

¹Department of Land Management, Zhejiang University, Hangzhou 310058, PR China

²Policy Simulation Laboratory, Zhejiang University, Hangzhou 310058, PR China

³College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, PR China

⁴Louis Bolk Institute, Hoofdstraat 24, 3972 LA Driebergen, The Netherlands

⁵VU Amsterdam, De Boelelaan 1091, 1081 HV Amsterdam, The Netherlands

⁶Netherlands Environmental Assessment Agency (PBL), Postbus 30314, The Netherlands

⁷NERC Centre for Ecology & Hydrology, Bush Estate, Penicuik, Midlothian, EH26 0QB, United Kingdom

⁸University of Exeter Medical School, Knowledge Spa, Truro, TR1 3HD, United Kingdom

⁹Crop and Soil Science Section, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Victoria 3010 Australia

¹⁰Department of Soil Quality, Wageningen University, P.O. Box 47, 6700 AA, Wageningen, The Netherlands

¹¹Department of Geography, Kent State University, Kent, OH 44242, USA

Abstract

Reactive nitrogen (Nr) is both a limiting nutrient for food production and a major cause of global environmental and climate change. Managing Nr is crucial for its sustainable use in an increasingly affluent society (Zhang et al., 2015), especially as it may compromise the mitigation of global warming through interactions with the carbon cycle (Zaehle et al., 2011). The relation between Nr creation/release and carbon dioxide (CO₂) emission/sequestration with respect to economic growth remains uncertain. Here we report on the turning points of Nr creation and release, and CO₂ emission in relation to the growth of gross domestic product (GDP) per capita. Nr creation increases with GDP per capita until reaching a turning point, after which it tends to decrease with further economic growth. A similar pattern is noted for CO₂ emission and Nr release to the atmosphere. However, the ratio of CO₂ emission to Nr release to the atmosphere increases with economic growth without any turning point. This phenomenon suggests that the carbon sink in terrestrial ecosystems will be limited by Nr availability with economic growth in the future, and managing Nr for sustainable development may compromise the mitigation of global warming. Integrated management of carbon and Nr is therefore critical for future sustainable development and mitigation to climate warming.