文摘
Background and aims High nitrous oxide (N2O) emissions may occur during the non-rice growing season of Chinese rice-upland crop rotation systems. However, our understanding of N2O emission during this season is poor due to a scarcity of available field N2O measurements. Methods Using the static manual chamber-GC technique, seasonal N2O emissions during the non-rice growing season were simultaneously measured at two adjacent rice-wheat and rice-rapeseed fields in southwest China for three consecutive annual rotation cycles (May 2005 to May 2008). Results Compared to the control, N fertilizer applications significantly enhanced soil N2O emissions from both wheat and rapeseed systems. Seasonal cumulative N2O fluxes from wheat systems were on average 2.6?kg?N?ha? for the recommended practice (RP [150?kg?N?ha?]) and 5.0?kg?N?ha? for the conventional practice (CP [250?kg?N?ha?]). Lower N2O emissions were observed from the adjacent rapeseed systems. Average cumulative seasonal N2O fluxes from rapeseed were 1.5 and 2.2?kg?N?ha? for the RP and CP treatments, respectively. The first 3?weeks after N fertilization were the “hot moment-of N2O emissions for both the wheat and rapeseed systems. The lowest yield-scaled N2O fluxes for wheat were obtained at the RP treatment (mean: 0.81?kg?N?Mg?) while for rapeseed the CP treatment produced the lowest yield-scaled fluxes (mean: 0.79?kg?N?Mg?). On average, the direct N2O emission factors (EFd) for the wheat system (1.76?%) were over two times higher than for the rapeseed system (0.73?%). Conclusions Intercropping of rapeseed tends to result in lower N2O emissions than wheat for rice-upland crop rotation systems of southwest China, indicating that either the N fertilization or the cropping system need to be considered not only for improving the estimate of regional and/or national N2O fluxes but also for proposing the climate-smart agricultural management practice to reduce N2O emissions from agricultural soils.