Fertilization scenarios in sprinkler irrigated corn under Mediterranean conditions: effects on greenhouse gas emissions

Agricultural soils emit greenhouse gases (GHG). Excessive application of N fertilizer may lead to the accumulation of mineral N in the soil, which is susceptible to loss to the environment. The objective of this study was to quantify the effect of two levels of available mineral N before planting (L, low; H, high) and two rates of NH4NO3 fertilizer (0 and 300 kg N ha(-1)) on soil CH4, CO2, and N2O emissions in a sprinkler-irrigated corn (Zea mays L.) field located in northeastern Spain during two growing seasons (2011 and 2012). For both soil N levels at planting, several sampling dates showed higher N2O emissions in the 300 kg N ha(-1) treatment than the 0 kg N ha(-1) treatment. Applications of N fertilizer resulted in a short-lived increase of N2O emitted. Differences among fertilization treatments were found for soil CO2 emissions in 2011 and for soil N2O emissions in 2011 and 2012. No differences were found between treatments for CH4. In the 2012 season, the application of 300 kg N ha(-1) in the L scenario reduced N2O yield-scaled emissions (g N2O-N kg(-1) aboveground N uptake) by 30% due to a significant increase in corn yield (7.6 Mg grain ha(-1)) compared with the treatment without N. Conversely, under the H scenario, N application doubled yield-scaled N2O emissions. Results of this study demonstrate that fertilization strategies need to take into account mineral N levels in the soil before sowing to reduce GHG emissions during the growing season.We would like to thank Ana Bielsa, Mónica Guillén, María José Salvador, and Javier Bareche for laboratory and field assistance. This work was partially supported by the Aragon Government and La Caixa (Grant GA-LC-050/2011), the Comisión Interministerial de Ciencia y Tecnología of Spain (Grants AGL2013-49062-C4-4-R, AGL2010- 22050-C03-01/02, and AGL2009-12897-C02-02), and the European Union (FEDER funds). Daniel Plaza-Bonilla received a “Juan de la Cierva” grant from the Ministerio de Economía y Competitividad of Spain. Finally, we are thankful to three anonymous reviewers for their valuable feedback and suggestions that led to further improvement of this manuscript