Effect of N dose on soil GHG emissions from a drip-fertigated olive (Olea europaea L.) orchard

Agronomic practices may mitigate greenhouse gas emissions (GHG) from crops. Appropriate nitrogen (N) and irrigation management provide the potential to reduce nitrous oxide (N₂O) and methane (CH₄) emissions. However, there is little information about the combination of both practices on the GHG emissions from olive orchards. This four-year study was conducted to qualitatively compare the effect of N doses applied through two drip irrigation strategies on N₂O and CH₄ emissions in a super-intensive (1010 trees ha^-1) olive orchard. The design (randomised blocks) was asymmetric: 0, 50 and 100 kg N ha^-1 yr^-1 were tested with full irrigation (FI; 2013 to 2016), but only 0 and 50 kg N ha^-1 yr^-1 were tested with regulated deficit irrigation (RDI; 2014 to 2016). The study shows that the soil acted as a main sink of N₂O and CH₄, regardless of the soil water content. Methane oxidation increased with N dose in the FI strategy (significant in 2013 and 2015). Overall, there was a tendency of yield to increase with the N dose without increasing emissions and without depending of the irrigation strategy. However, these results were not significant. Further confirmation of this tendency is necessary; particularly comparing FI + N100 (most promising treatment in terms of profitability) with the RDI + N100 (not available in this study) water-saving strategy.