ChileanJAR

Chile has different types of soil and climate conditions that favor a wide range of agricultural activities that can generate potential atmospheric contamination like greenhouse gases (GHG). Nevertheless, the contribution of agricultural soils to atmospheric emissions has yet to be measured in Chile. The aim of this study was to assess seasonal variability of CO₂ and N₂O effluxes in situ from a volcanic ash-derived soil under different agronomic management practices. Gas samples were obtained from headspaces of non-fixed closed chambers in an annual crop rotation under a no-till system in an Andisol in southern Chile (36° S). Two N-sources (NH₄⁺ and NO₃^-) and ammonium fertilization plus two lime doses (0.5 and 1 Mg ha^-1) were considered for soil treatments Effluxes of CO₂ and N₂O were determined periodically for 1 yr, and soil variables, such as temperature, water, and mineral N content, were recorded. Results showed that CO₂ effluxes respond to a seasonal pattern. No effect was evidenced when considering crop management practices with a maximum of 53.2 ± 8.5 kg CO₂-C ha^-1 d^-1 in the wet fall period and a minimum of 9.7 ± 2.1 kg CO₂-C ha^-1 d^-1 for summer, fall dry period, and winter. N₂O efflux was highly variable throughout the year and showed no influence of treatments or season variability with a mean of 0.95 kg N₂O-N ha^-1 yr^-1. Soil mineral N variations are not related to GHG effluxes as a single variable. Results indicate that an Andisol under a no-till system in southern Chile has a low N₂O emission potential, and higher CO₂ emissions are mainly produced in wet seasons (wet fall and/or spring).