Inhibitor-coated enhanced-efficiency N fertilizers for mitigating NOx and N2O emissions in a high-temperature irrigated agroecosystem

Nitrogen (N) fertilizers have substantially increased global crop yields around the world during recent decades. Nevertheless, the extensive use of N fertilizers at global scale has converted agricultural fertilized soils into an important anthropogenic source of nitrous oxide (N2O) and nitric oxides (NO+NO2 = NOx). The application of enhanced-efficiency N fertilizers, with the addition of urease and nitrification inhibitors (UI and NI, respectively), facilitates the reduction of N2O and NOx emissions and the improvement of agronomic responses. Despite the fact that soil N2O emissions have been widely studied under a large variety of climatic conditions and with different enhanced-efficiency N fertilizer, few studies have focused on soil NOx emissions, particularly in high temperature environments. The main aim of this study, therefore, was the quantification of NO and NO2 fluxes at a high temporal resolution using an automatic measurement system with the capacity to evaluate 5 different treatments with three replicates, and the ambient gas concentration. In addition, N2O emissions were measured with the static chamber method. With respect to the urea (U) treatment, the results confirm a significant mitigation of N2O and NO losses with the use of the new experimental inhibitor, DMPSA, alone or combined with the urease inhibitor NBPT. Overall, NOx emissions decreased by more than 60% in all the treatments in which synthetic inhibitors (both UI and NI) were applied, while N2O emissions were reduced by more than 35% in all the fertilized treatments when compared with urea alone. The high temporal resolution allowed the observation of negative fluxes of NO and NO2 in the different treatments, although these were more frequent and intense in the U+NI treatment. In general, grain and biomass yield were not affected by the use of NI or UI. The combined result was that a substantial reduction of yield-scaled-N2O and yield-scaled-NOx emissions was obtained when these inhibitors were used with urea and, therefore, their use should be recommended for mitigating these emissions whilst maintaining yields.