title: Global nitrogen budgets in cereals: A 50-year assessment for maize, rice, and wheat production systems.
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 N2 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 N2 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.
authors.affiliation: International Rice Research Institute, IRRI-India, NASC Complex, DPS Marg, Pusa, New Delhi 110012, India.
authors.forename: J K
authors.initials: JK
authors.lastname: Ladha
authors.affiliation: International Rice Research Institute, IRRI-India, NASC Complex, DPS Marg, Pusa, New Delhi 110012, India.
authors.forename: A
authors.initials: A
authors.lastname: Tirol-Padre
authors.affiliation: International Rice Research Institute, IRRI-India, NASC Complex, DPS Marg, Pusa, New Delhi 110012, India.
authors.forename: C K
authors.initials: CK
authors.lastname: Reddy
authors.affiliation: University of Nebraska, Department of Agronomy and Horticulture, 234 Whittier Research Building, Lincoln LE 68583-0857, USA.
authors.forename: K G
authors.initials: KG
authors.lastname: Cassman
authors.affiliation: Dr. YS Parmar University of Horticulture &Forestry, Department of Soil Science &Water Management, Nauni, Solan - 173 230, Himachal Pradesh, India.
authors.forename: Sudhir
authors.initials: S
authors.lastname: Verma
authors.affiliation: Rothamsted Research, Department of Sustainable Soils &Grassland Systems, Harpenden, Herts, AL5 2JQ, UK.
authors.forename: D S
authors.initials: DS
authors.lastname: Powlson
authors.affiliation: University of California, Davis, Department of Plant Sciences, 1 Shields Avenue, Davis, CA 95616, USA.
authors.forename: C
authors.initials: C
authors.lastname: van Kessel
authors.affiliation: Nicholas School of Environment, Duke University, Durham, NC 27708, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: de B Richter
authors.affiliation: Indian Agricultural Research Institute, Division of Agricultural Physics, Pusa Campus, New Delhi 110012, India.
authors.forename: Debashis
authors.initials: D
authors.lastname: Chakraborty
authors.affiliation: Indian Agricultural Research Institute, Centre for Environment Science and Climate Resilient Agriculture, Pusa Campus, New Delhi, 110012, India.
authors.forename: Himanshu
authors.initials: H
authors.lastname: Pathak
mesh_terms: D000069599:Crop Production / Q000191:economics* / Q000266:history / Q000639:trends; D002523:Edible Grain; D005308:Fertilizers / Q000191:economics*; D049673:History, 20th Century; D049674:History, 21st Century; D006801:Humans; D009584:Nitrogen; D012275:Oryza; D014908:Triticum; D003313:Zea mays
chemical_list: D005308:Fertilizers; D009584:Nitrogen