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      Global nitrogen budgets in cereals: A 50-year assessment for maize, rice, and wheat production systems

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          Abstract

          Industrially produced N-fertilizer is essential to the production of cereals that supports current and projected human populations. We constructed a top-down global N budget for maize, rice, and wheat for a 50-year period (1961 to 2010). Cereals harvested a total of 1551 Tg of N, of which 48% was supplied through fertilizer-N and 4% came from net soil depletion. An estimated 48% (737 Tg) of crop N, equal to 29, 38, and 25 kg ha −1 yr −1 for maize, rice, and wheat, respectively, is contributed by sources other than fertilizer- or soil-N. Non-symbiotic N 2 fixation appears to be the major source of this N, which is 370 Tg or 24% of total N in the crop, corresponding to 13, 22, and 13 kg ha −1 yr −1 for maize, rice, and wheat, respectively. Manure (217 Tg or 14%) and atmospheric deposition (96 Tg or 6%) are the other sources of N. Crop residues and seed contribute marginally. Our scaling-down approach to estimate the contribution of non-symbiotic N 2 fixation is robust because it focuses on global quantities of N in sources and sinks that are easier to estimate, in contrast to estimating N losses per se, because losses are highly soil-, climate-, and crop-specific.

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          Most cited references34

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          Transformation of the nitrogen cycle: recent trends, questions, and potential solutions.

          Humans continue to transform the global nitrogen cycle at a record pace, reflecting an increased combustion of fossil fuels, growing demand for nitrogen in agriculture and industry, and pervasive inefficiencies in its use. Much anthropogenic nitrogen is lost to air, water, and land to cause a cascade of environmental and human health problems. Simultaneously, food production in some parts of the world is nitrogen-deficient, highlighting inequities in the distribution of nitrogen-containing fertilizers. Optimizing the need for a key human resource while minimizing its negative consequences requires an integrated interdisciplinary approach and the development of strategies to decrease nitrogen-containing waste.
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            Enhanced nitrogen deposition over China.

            China is experiencing intense air pollution caused in large part by anthropogenic emissions of reactive nitrogen. These emissions result in the deposition of atmospheric nitrogen (N) in terrestrial and aquatic ecosystems, with implications for human and ecosystem health, greenhouse gas balances and biological diversity. However, information on the magnitude and environmental impact of N deposition in China is limited. Here we use nationwide data sets on bulk N deposition, plant foliar N and crop N uptake (from long-term unfertilized soils) to evaluate N deposition dynamics and their effect on ecosystems across China between 1980 and 2010. We find that the average annual bulk deposition of N increased by approximately 8 kilograms of nitrogen per hectare (P < 0.001) between the 1980s (13.2 kilograms of nitrogen per hectare) and the 2000s (21.1 kilograms of nitrogen per hectare). Nitrogen deposition rates in the industrialized and agriculturally intensified regions of China are as high as the peak levels of deposition in northwestern Europe in the 1980s, before the introduction of mitigation measures. Nitrogen from ammonium (NH4(+)) is the dominant form of N in bulk deposition, but the rate of increase is largest for deposition of N from nitrate (NO3(-)), in agreement with decreased ratios of NH3 to NOx emissions since 1980. We also find that the impact of N deposition on Chinese ecosystems includes significantly increased plant foliar N concentrations in natural and semi-natural (that is, non-agricultural) ecosystems and increased crop N uptake from long-term-unfertilized croplands. China and other economies are facing a continuing challenge to reduce emissions of reactive nitrogen, N deposition and their negative effects on human health and the environment.
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              Nitrogen Cycles: Past, Present, and Future

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                Author and article information

                Journal
                Sci Rep
                Sci Rep
                Scientific Reports
                Nature Publishing Group
                2045-2322
                18 January 2016
                2016
                : 6
                : 19355
                Affiliations
                [1 ]International Rice Research Institute, IRRI-India, NASC Complex , DPS Marg, Pusa, New Delhi 110012, India
                [2 ]University of Nebraska, Department of Agronomy and Horticulture , 234 Whittier Research Building, Lincoln LE 68583-0857, USA
                [3 ]Dr. YS Parmar University of Horticulture & Forestry, Department of Soil Science & Water Management , Nauni, Solan - 173 230, Himachal Pradesh, India
                [4 ]Rothamsted Research, Department of Sustainable Soils & Grassland Systems , Harpenden, Herts, AL5 2JQ, UK
                [5 ]University of California, Davis, Department of Plant Sciences , 1 Shields Avenue, Davis, CA 95616, USA
                [6 ]Nicholas School of Environment, Duke University , Durham, NC 27708, USA
                [7 ]Indian Agricultural Research Institute, Division of Agricultural Physics , Pusa Campus, New Delhi 110012, India
                [8 ]Indian Agricultural Research Institute, Centre for Environment Science and Climate Resilient Agriculture , Pusa Campus, New Delhi, 110012, India
                Author notes
                Article
                srep19355
                10.1038/srep19355
                4726071
                26778035
                0bdff3c6-2c5b-4d23-9e19-4f83be44cf77
                Copyright © 2016, Macmillan Publishers Limited

                This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/

                History
                : 09 October 2015
                : 11 December 2015
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