Linear and nonlinear dependency of direct nitrous oxide emissions on fertilizer nitrogen input: A meta-analysis

• Published in: Agriculture, ecosystems & environment Vol. 168; pp. 53 - 65
• Main Authors: Kim, Dong-Gill, Hernandez-Ramirez, Guillermo, Giltrap, Donna
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier B.V 15.03.2013; Elsevier
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; carbon; carbon footprint; data collection; ecosystems; Emission factor; Fundamental and applied biological sciences. Psychology; General agroecology; General agroecology. Agricultural and farming systems. Agricultural development. Rural area planning. Landscaping; General agronomy. Plant production; Generalities. Agricultural and farming systems. Agricultural development; global warming; greenhouse gas emissions; IPCC methodology; Meta-analysis; nitrogen; nitrogen fertilizers; Nitrogen input; Nitrogen, phosphorus, potassium fertilizations; Nitrous oxide; Open-access database; soil quality; Soil-plant relationships. Soil fertility. Fertilization. Amendments; IPCC methodology; Emission factor; Open-access database; Nitrous oxide; Nitrogen input; Meta-analysis; Gas emission; Ecology; Nitrogen; Metaanalysis; Dynamical climatology; Climate change; Intergovernmental Panel on Climate Change; Database; Nonlinearity; Nitrogen protoxide; Nitrogen fertilizer; Open access
• ISSN: 0167-8809; 1873-2305
• DOI: 10.1016/j.agee.2012.02.021

► Dependency of direct N2O emission on N input examined using 26 published datasets. ► N2O response to increased N additions was non-linear in more cases than linear. ► Direct N2O emission factor remains constant or changes nonlinearly with N input. ► We propose a relationship describing N2O response to increasing N input rates. Rising atmospheric concentrations of nitrous oxide (N2O) contribute to global warming and associated climate change. It is often assumed that there is a linear relationship between nitrogen (N) input and direct N2O emission in managed ecosystems and, therefore, direct N2O emission for national greenhouse gas inventories use constant emission factors (EF). However, a growing body of studies shows that increases in direct N2O emission are related by a nonlinear relationship to increasing N input. We examined the dependency of direct N2O emission on N input using 26 published datasets where at least four different levels of N input had been applied. In 18 of these datasets the relationship of direct N2O emission to N input was nonlinear (exponential or hyperbolic) while the relationship was linear in four datasets. We also found that direct N2O EF remains constant or increases or decreases nonlinearly with changing N input. Studies show that direct N2O emissions increase abruptly at N input rates above plant uptake capacity. The remaining surplus N could serve as source of additional N2O production, and also indirectly promote N2O production by inhibiting biochemical N2O reduction. Accordingly, we propose a hypothetical relationship to conceptually describe in three steps the response of direct N2O emissions to increasing N input rates: (1) linear (N limited soil condition), (2) exponential, and (3) steady-state (carbon (C) limited soil condition). In this study, due to the limited availability of data, it was not possible to assess these hypothetical explanations fully. We recommend further comprehensive experimental examination and simulation using process-based models be conducted to address the issues reported in this review.