The utility of a boundary line approach for simulating denitrification and nitrous oxide emissions from a Regosol under summer maize-winter wheat crop rotation in Southwest China

Despite the ever-increasing measurements of denitrification and nitrous oxide (N2O) emissions globally, boundary line analyses of these important processes have only been applied to a limited number of agroecosystems. The primary aims of this study were to determine the responses of denitrification and N2O emissions from a subtropical cropland to several soil parameters through boundary line analyses, and to evaluate the ability of site-specific boundary line models for simulating gaseous nitrogen (N) losses using available soil parameters. We performed 403 measurements of denitrification and N2O emissions from two fields cropped with a winter wheat-summer maize rotation in the Sichuan Basin, Southwest China, from October 2004 to September 2005. Boundary lines were fitted for denitrification and N2O emission data against soil temperature, water content, ammonium and/or nitrate substrates, and heterotrophic respiration rates. The boundary lines were largely in agreement with existing theoretical concepts. By incorporating the regulatory effects of soil temperature, water content, N substrates, and an unknown factor that could be related to ammoniumcontent, the boundary linemodels reasonably simulated the seasonal variations in denitrification and N2O emissions thatwere collected froma field trial in the same region during the maize season in 2012. The models overestimated the denitrification and N2O emissions on the sampling dates by 8% and 22% on average, respectively. We conclude that boundary linemodels are useful tools for estimating gaseous N losses from a given cropland. However, the application of the models is limited by the availability of input data. (C) 2020 Elsevier B.V. All rights reserved.