The factors related to carbon dioxide effluxes and production in the soil profiles of rain-fed maize fields

We assessed soil carbon dioxide (CO2) production and transport in high-yield fields and confirmed the main sources and main driving factors of CO2 at different soil depths. Our experiments were performed at the Changwu ecological station, and we utilized a 3-year-old fertility experiment to study the production and effluxes of CO2 within soil profiles. Soil CO2 efflux rates were computed by the concentration gradient method, where CO2 concentrations were measured using flame ionization detector (FID) from situ gas samplers. The results showed that the cumulative production and effluxes of CO2 in the soil decreased with depth; most of CO2 soil production and effluxes occurred in the surface soil (0-15 cm), where the cumulative production and effluxes of CO2 accounted for 723% and 76.3% of the total amounts in the soil profile (0-100 cm), respectively. Higher efflux rates were observed with high production rates from the sixth-leaf stage (V6) to the silking stage (R1), which is a period of rapid maize growth and soil water stress. During that period, mean cumulative effluxes accounted for 52-57% of the annual effluxes. The application of nitrogen fertilizer strongly improved plant growth and grain yield and slightly promoted CO2 production and effluxes. However, nitrogen fertilizer application did not affect the productive contribution rate, i.e., the contribution rate of CO2 production in each soil layer to the entire profile (% of total), which revealed that the production and effluxes of CO2 responded weakly to nitrogen fertilizer. The integrated application of manure and nitrogen fertilizer significantly increased the production and effluxes of CO2 within the soil profiles and significantly improved the productive contribution rates of CO2 in the topsoil. In addition, manure application promoted much greater soil CO2 production throughout the observation period, so the contribution from manure was greater than that from nitrogen fertilizer. (C) 2015 Elsevier B.V. All rights reserved.