Nitrous oxide (N2O) emissions from the Chilean agricultural sector are primarily associated with the use of nitrogen (N) fertilizers, so that the use of nitrification and urease inhibitors May represent a potential mitigation option. However, their effectiveness in volcanic ash soils with high organic matter is still uncertain. In this study, the effect of Dicyandiamide (DCD) and N-(n-butyl) thiophosphoric triamide (NBPT) on soil N2O and CH4 emissions from an oat crop was determined using a fully automated greenhouse gas measuring system. Three urea treatments were evaluated: 120 kg N ha(-1), 120 kg N ha(-1) + DCD and 120 kg N ha(-1) + NBPT (n=3). A zero treatment (-N) was also considered. Annual N2O emissions ranged from 0.36 to 1.00 kg N2O-N ha(-1) (P >0.05) whereas the net uptake of CH4 ranged from 6.72 to 7.00 kg CH4-C ha(-1) (P> 0.05). Increases in N2O emissions were associated with rainfall events, as characteristic of Mediterranean rain fed ecosystems. Soil CH4 uptake did not vary among treatments but had a significant role offsetting N2O emissions, resulting in total emissions ranging from -17.1 to 239.0 kg CO2eq ha(-1) (P <0.001). There was no significant effect of DCD or NBPT on average soil mineral N concentration, and total N2O and CH4 emissions. NBPT significantly increased crop yield and crop N uptake by 27% and 33% respectively (P < 0.05), resulting in greater N use efficiency. The use of DCD did not increase productive parameters, but resulted in a 35% reduction of the N2O-N emission intensity (P < 0.05). The study shows that volcanic ash soils have a relatively low N2O emission potential due to physic-chemical characteristics and that NBPT could be used to increase N use efficiency in crops, while DCD has a potential to reduce N2O losses per unit yield. (C) 2016 Elsevier B.V. All rights reserved.