Processes and factors controlling N2O production in an intensively managed low carbon calcareous soil under sub-humid monsoon conditions

An automated system for continuous measurement of N2O fluxes on an hourly basis was employed to study N2O emissions in an intensively managed low carbon calcareous soil under sub-humid temperate monsoon conditions. N2O emissions occurred mainly within two weeks of application of NH4+-based fertilizer and total N2O emissions in wheat (average 0.35 or 0.21 kg N ha(-1) season(-1)) and maize (average 1.47 or 0.49 kg N ha(-1) season(-1)) under conventional and optimum N fertilization (300 and 50-122 kg N ha(-1), respectively) were lower than previously reported from low frequency measurements. Results from closed static chamber showed that N2O was produced mainly from nitrification of NH4+-based fertilizer, with little denitrification occurring due to limited readily oxidizable carbon and low soil moisture despite consistently high soil nitrate-N concentrations. Significant reductions in N2O emissions can be achieved by optimizing fertilizer N rates, using nitrification inhibitors, or changing from NH4+- to NO3--based fertilizers. (C) 2011 Elsevier Ltd. All rights reserved.