Nitrous oxide emissions from applied nitrate fertiliser in commercial cherry orchards

Abstract

The application of nitrate (NO3–) fertiliser is important worldwide in providing nitrogen (N) nutrition to perennial fruit trees. There is little information available on N losses to the environment from commercial cherry orchards, in relation to different timings of NO3– application. The emission of nitrous oxide (N2O) gas is an important greenhouse gas loss from NO3– application, being responsible for 6% of anthropogenic global warming and a catalyst for depletion of stratospheric ozone. In a commercial sweet-cherry orchard in southern Tasmania, we applied 373 g NO3–-N m–2 (equivalent to 90 kg NO3–-N ha–1) either pre- or post-harvest, or equally split between the two, to study the resultant N2O emissions. Emissions averaged 8.37 mg N2O-N m–2 day–1 during the pre-harvest period, primarily driven by a heavy rainfall event, and were significantly greater (P < 0.05) than the average 4.88 × 10–1 mg N2O-N m–2 day–1 from post-harvest NO3– application. Discounting the emissions related to the rainfall event, the resultant average 1.88 mg N2O-N m–2 day–1 for the rest of the pre-harvest emissions remained significantly greater (P < 0.05) than those post-harvest. Ongoing studies will help to build on these results and efforts to minimise N2O emissions in perennial tree cropping systems.