Processes and factors controlling N_2O production in an intensively managed low carbon calcareous soil under sub-humid monsoon conditions

摘要

An automated system for continuous measurement of N_2O fluxes on an hourly basis was employed to study N_2O emissions in an intensively managed low carbon calcareous soil under sub-humid temperate monsoon conditions. N_2O emissions occurred mainly within two weeks of application of NH_4~+-based fertilizer and total N_2O 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 N_2O was produced mainly from nitrification of NH_4~+-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 N_2O emissions can be achieved by optimizing fertilizer N rates, using nitrification inhibitors, or changing from NH_4~+- to NO_3~--based fertilizers.