Understanding the role of nitrogen management in apple orcharding to mitigate nitrous oxide emissions

Intensively managed agricultural systems such as tree-crop orcharding can cause rapid oxidation of carbon and nitrogen (N) leading to high CO₂ and N₂O emissions. Currently there is little data available to estimate GHG emissions from tree-crop systems. We investigated the effect of nitrate application and irrigation on N₂O emissions in a 10-year-old ‘Galaxy’ apple orchard in the cool temperate Huon Valley of southern Tasmania. Fertilizer treatments were applied by fertigation in spring (pre-harvest) and late summer (post-harvest) along with high, medium and low rates of irrigation. N₂0 and C0₂ were collected from static chambers installed within the tree-line, and in the inter-row of the orchard 0, 30 and 60 mins after sealing the chambers. Gas concentrations were analysed using gas chromatography. Soil moisture and soil and air temperature were monitored daily and N content in leaf, fruit and soil were collected pre- and post-fertigation and at harvest. Results will demonstrate the effect of N application, irrigation, temperature and position within the orchard on GHG emissions. Optimising fertilizer rate and timing in combination with irrigation management provides potential for reducing N₂O emissions in temperate tree production horticulture.