Effect of irrigation, nitrogen application, and a nitrification inhibitor on nitrous oxide, carbon dioxide and methane emissions from an olive (Olea europaea L.) orchard.

Abstract Drip irrigation combined with nitrogen (N) fertigation is applied in order to save water and improve nutrient efficiency. Nitrification inhibitors reduce greenhouse gas emissions. A field study was conducted to compare the emissions of nitrous oxide (N 2 O), carbon dioxide (CO 2 ) and methane (CH 4 ) associated with the application of N fertiliser through fertigation (0 and 50 kg N ha −1 ), and 50 kg N ha −1  + nitrification inhibitor in a high tree density Arbequina olive orchard. Spanish Arbequina is the most suited variety for super intensive olive groves. This system allows reducing production costs and increases crop yield. Moreover its oil has excellent sensorial features. Subsurface drip irrigation markedly reduced N 2 O and N 2 O + N 2 emissions compared with surface drip irrigation. Fertiliser application significantly increased N 2 O + N 2 , but not N 2 O emissions. Denitrification was the main source of N 2 O. The N 2 O losses (calculated as emission factor) ranging from − 0.03 to 0.14% of the N applied, were lower than the IPCC (2007) values. The N 2 O + N 2 losses were the largest, equivalent to 1.80% of the N applied, from the 50 kg N ha −1  + drip irrigation treatment which resulted in water filled pore space > 60% most of the time (high moisture). Nitrogen fertilisation significantly reduced CO 2 emissions in 2011, but only for the subsurface drip irrigation strategies in 2012. The olive orchard acted as a net CH 4 sink for all the treatments. Applying a nitrification inhibitor (DMPP), the cumulative N 2 O and N 2 O + N 2 emissions were significantly reduced with respect to the control. The DMPP also inhibited CO 2 emissions and significantly increased CH 4 oxidation. Considering global warming potential, greenhouse gas intensity, cumulative N 2 O emissions and oil production, it can be concluded that applying DMPP with 50 kg N ha −1  + drip irrigation treatment was the best option combining productivity with keeping greenhouse gas emissions under control.