Shanchao Yue

Characteristics of N2O production and transport within soil profiles subjected to different nitrogen application rates in China.

To better understand the effect of N fertilizer on the responses of subsoil N2O to N2O emissions in a high-yield plot, we investigated the subsurface N2O concentrations at seven mineral soil depths and analyzed the subsoil N2O fluxes between soil horizons. This study was conducted from 2012 to 2013 in farmland located in the semi-humid area of the Changwu station, Shaanxi, and the results showed that the application of N fertilizer triggered the highest amount of N2O production and effluxes in the various soil layers. With an increase of N fertilizer, N2O effluxes and production significantly increased; the mean variation of 380 kg N ha(-1) treatment was much greater than that of 250 kg N ha(-1) treatment, particularly after fertilization during the maize growing season (MS). N2O concentrations increased within 30 cm and maintained low and stable values. However, N2O fluxes and production decreased with depth (below 30 cm) and then remained low (approximately zero or even negative) at depths of 30-90 cm. The cumulative N2O fluxes in the 0-15 cm soil layer accounted for 99.0% of the total amount in the soil profile, and high fluxes coincided with periods of relatively high production rates. The cumulative production of N2O also remained in step with the cumulative fluxes. In addition, more N fertilizer was applied, greater production occurred in the topsoil. A significantly positive relationship was found between N2O fluxes and mineral N, and a negative relationship was found between the fluxes and the water-filled pore space (WFPS) in the shallow soil. N2O effluxes increased with increasing amounts of N fertilizer, which was primarily due to nitrification on the Loess Plateau.

Effects of plastic film mulching on soil greenhouse gases (CO2, CH4 and N2O) concentration within soil profiles in maize fields on the Loess Plateau, China

Abstract To better understand the effects of plastic film mulching on soil greenhouse gases (GHGs) emissions, we compared seasonal and vertical variations of GHG concentrations at seven soil depths in maize (Zea mays L.) fields at Changwu station in Shaanxi, a semi-humid region, between 2012 and 2013. Gas samples were taken simultaneously every one week from non-mulched (BP) and plastic film-mulched (FM) field plots. The results showed that the concentration of GHGs varied distinctly at the soil-atmosphere interface and in the soil profile during the maize growing season (MS). Both carbon dioxide (CO2) and nitrous oxide (N2O) concentrations increased with increasement of soil depth, while the methane (CH4) concentrations decreased with increasement of soil depth. A strong seasonal variation pattern was found for CO2 and N2O concentrations, as compared to an inconspicuous seasonal variation of CH4 concentrations. The mean CO2 and N2O concentrations were higher, but the mean CH4 concentration in the soil profiles was lower in the FM plots than in the BP plots. The results of this study suggested that plastic film mulching significantly increased the potential emissions of CO2 and N2O from the soil, and promoted CH4 absorption by the soil, particularly during the MS.