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In newly irrigated Mediterranean agroecosystems, the combined effect of tillage and N fertilization on soilcarbon dioxide (CO2) and methane (CH4)fluxes is at present poorly understood. The goal of this study was toquantify both soil CO2and CH4emissions as well as crop performance under different tillage systems and Nfertilization rates during three maize (Zea maysL.) growing seasons (2015-2017) in a semiarid area converted toirrigated. Three types of tillage (conventional tillage, CT, reduced tillage, RT, and no-tillage, NT) and threemineral N fertilization rates (0, 200, and 400 kg N ha−1) were compared in a randomized block design withthree replications. Weekly soil CO2and CH4emissions, soil temperature and gravimetric moisture were mea-sured. Moreover, maize above-ground biomass, grain yield, and above-ground C-inputs were quantified. Carbondioxide emissions ranged from 173 to 4378 mg CO2-C m-2d-1. No-tillage showed a greater mean soil CO2fluxthan CT when applying the highest rate of N (400 kg N ha-1). Although some emissions of CH4were observed, alltreatments acted as net CH4sinks during most of the experimental period. A linear multiple relationship betweensoil CO2fluxes and soil gravimetric moisture (0-5 cm depth) and temperature (10 cm depth) were found. In the2015 growing season, greater cumulative CO2emissions were found under NT and RT compared with CT, whilein 2016 N T showed the highest values compared to CT with intermediate values in RT. Differently, in 2017 nodifferences between tillage systems were found. When applying N fertilizer, NT and RT increased maize grainproduction and above-ground C-inputs compared to CT, since a severe soil crusting occurred in this last, whichcaused crop water deficit. The results suggest that tillage intensity and N fertilization rate reduction can increasemaize biomass production and yield which leads to greater C-input that returns to the soil.
We would like to thank the field and laboratory technicians Carlos Cortés, Barbara Jelcic, Javier Bareche and Silvia Martí. This research work was financially supported by the Ministerio de Economía y Competitividad of Spain (project AGL2013-49062-C4-1-R; PhD fellowship BES‐2014‐070039). DPB received a Juan de la Cierva postdoctoral grant from the Ministerio de Economía y Competitividad of Spain (IJCI-2016-27784). |
