title: Direct Nitrous Oxide Emissions From Tropical And Sub-Tropical Agricultural Systems - A Review And Modelling Of Emission Factors.
abstract: There has been much debate about the uncertainties associated with the estimation of direct and indirect agricultural nitrous oxide (N2O) emissions in developing countries and in particular from tropical regions. In this study, we report an up-to-date review of the information published in peer-review journals on direct N2O emissions from agricultural systems in tropical and sub-tropical regions. We statistically analyze net-N2O-N emissions to estimate tropic-specific annual N2O emission factors (N2O-EFs) using a Generalized Additive Mixed Model (GAMM) which allowed the effects of multiple covariates to be modelled as linear or smooth non-linear continuous functions. Overall the mean N2O-EF was 1.2% for the tropics and sub-tropics, thus within the uncertainty range of IPCC-EF. On a regional basis, mean N2O-EFs were 1.4% for Africa, 1.1%, for Asia, 0.9% for Australia and 1.3% for Central &South America. Our annual N2O-EFs, estimated for a range of fertiliser rates using the available data, do not support recent studies hypothesising non-linear increase N2O-EFs as a function of applied N. Our findings highlight that in reporting annual N2O emissions and estimating N2O-EFs, particular attention should be paid in modelling the effect of study length on response of N2O.
authors.affiliation: Institute of Biological &Environmental Sciences, School of Biological Sciences, University of Aberdeen, Cruickshank Building, St. Machar Drive, Aberdeen AB24 3UU, UK.
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Albanito
authors.affiliation: Research Centre Hanninghof, Yara International ASA, Hanninghof 35, 48249, Duelmen, Germany.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Lebender
authors.affiliation: Institute of Biological &Environmental Sciences, School of Biological Sciences, University of Aberdeen, Cruickshank Building, St. Machar Drive, Aberdeen AB24 3UU, UK.
authors.forename: Thomas
authors.initials: T
authors.lastname: Cornulier
authors.affiliation: International Maize and Wheat Improvement Center (CIMMYT), Sustainable Intensification Program, NASC complex, New Delhi 110012, India.
authors.forename: Tek B
authors.initials: TB
authors.lastname: Sapkota
authors.affiliation: Research Centre Hanninghof, Yara International ASA, Hanninghof 35, 48249, Duelmen, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Brentrup
authors.affiliation: International Maize and Wheat Improvement Center (CIMMYT), Sustainable Intensification Program, Apdo. Postal 6-641 06600 Mexico, D.F., Mexico.
authors.forename: Clare
authors.initials: C
authors.lastname: Stirling
authors.affiliation: Institute of Biological &Environmental Sciences, School of Biological Sciences, University of Aberdeen, Cruickshank Building, St. Machar Drive, Aberdeen AB24 3UU, UK.
authors.forename: Jon
authors.initials: J
authors.lastname: Hillier