Effect of N dose, fertilisation duration and application of a nitrification inhibitor on GHG emissions from a peach orchard.

Despite only occupying 5% of the worldwide arable area, fruit tree crops are of vital economic importance in many regions. Intensive cropping practices can lead to greenhouse gas (GHG) emissions. In order to reduce these emissions, numerous studies have been made on lowering N inputs or applying nitrification inhibitors (NIs) which tend to maintain or even increase yield while reducing N leaching and nitrogenous emissions to the atmosphere. However, very few studies have been conducted on potential GHG emissions from the peach crop. In this work, a three-year study was carried out in a commercial peach orchard with a split-plot design with three replicates, in which the main factor was N dose (25, 50 and 100 kg N ha-1 year-1, and 50 kg N ha-1 year-1 applied during a shorter period of time in 2015 and 2016; and only 70 kg N ha-1 year-1 in 2017). Subplots in the study were used to analyse the effect of the application of a NI (3,4-dimethylpyrazole phosphate; DMPP). The aim was to qualitatively compare the effect of these factors on N2O, N2O + N2, CH4 and CO2 emissions from a peach orchard soil in order to recommend agricultural practices that minimise emissions without concurrent yield reductions. We show that N2O and N2O + N2 emissions were linked to fertilisation and increased with N dose. The N2O emissions were mitigated (up to 49%) by DMPP up to the 50 kg N ha-1 dose (not significantly). It seems that between 70 and 100 kg N ha-1 the application of DMPP loses effectiveness. Methane oxidation increased with N dose and decreased with DMPP application; CO2 emissions increased with DMPP and were unaffected by N dose. The intermediate N dose (50 kg N ha-1) applied during a shorter period of time increased yield (not significantly) and NUE without increasing GHG emissions.

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.

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

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 (N2O), carbon dioxide (CO2) and methane (CH4) associated with the application of N fertiliser through fertigation (0 and 50kgNha(-1)), and 50kgNha(-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 N2O and N2O+N2 emissions compared with surface drip irrigation. Fertiliser application significantly increased N2O+N2, but not N2O emissions. Denitrification was the main source of N2O. The N2O losses (calculated as emission factor) ranging from -0.03 to 0.14% of the N applied, were lower than the IPCC (2007) values. The N2O+N2 losses were the largest, equivalent to 1.80% of the N applied, from the 50kgNha(-1)+drip irrigation treatment which resulted in water filled pore space >60% most of the time (high moisture). Nitrogen fertilisation significantly reduced CO2 emissions in 2011, but only for the subsurface drip irrigation strategies in 2012. The olive orchard acted as a net CH4 sink for all the treatments. Applying a nitrification inhibitor (DMPP), the cumulative N2O and N2O+N2 emissions were significantly reduced with respect to the control. The DMPP also inhibited CO2 emissions and significantly increased CH4 oxidation. Considering global warming potential, greenhouse gas intensity, cumulative N2O emissions and oil production, it can be concluded that applying DMPP with 50kgNha(-1)+drip irrigation treatment was the best option combining productivity with keeping greenhouse gas emissions under control.

Changes in fine root production and longevity in relation to water and nutrient availability in a Norway spruce stand in northern Sweden.

The PEACH computer simulation model of reproductive and vegetative growth of peach trees (Grossman and DeJong 1994) was adapted to estimate seasonal nitrogen (N) dynamics in organs of mature peach (Prunus persica (L.) Batsch cv. O'Henry) trees grown with high and low soil N availability. Seasonal N accumulation patterns of fruits, leaves, stems, branches, trunk and roots of mature, cropping peach trees were modeled by combining model predictions of organ dry mass accumulation from the PEACH model with measured seasonal organ N concentrations of trees that had been fertilized with either zero or 200 kg N ha(-1) in April. The results provided a comparison of the N use of perennial and annual organs during the growing season for trees growing under both low and high N availability. Nitrogen fertilization increased tree N content by increasing organ dry masses and N concentrations during the fruit growing season. Dry mass of current-year vegetative growth was most affected by N fertilization. Whole-tree N content of fertilized trees was almost twice that of non-fertilized trees. Although N use was higher in fertilized trees, calculated seasonal N accumulation patterns were similar for trees in both treatments. Annual organs exhibited greater responses to N fertilization than perennial organs. Estimated mean daily N use per tree remained nearly constant from 40 days after anthesis to harvest. The calculations indicated that fertilized trees accumulated about 1 g N tree(-1) day(-1), twice that accumulated by non-fertilized trees. Daily N use by the fertilized orchard was calculated to be approximately 1 kg N ha(-1), whereas it was approximately 0.5 kg N ha(-1) for the non-fertilized trees. During the first 25-30 days of the growing season, all N use by growing tissues was apparently supplied by storage organs. Nitrogen release from storage organs for current growth continued until about 75 days after anthesis in both N treatments.